Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 14-Day Trial for You or Your Team.

Learn More →

Variability and adaptability of Miscanthus species evaluated for energy crop domestication

Variability and adaptability of Miscanthus species evaluated for energy crop domestication Introduction Miscanthus is considered to be a promising candidate for second‐generation energy crops ( Clifton‐Brown , 2004, 2007; Karp & Shield, 2008; Oliver , 2009 ). As a C4 perennial grass capable of producing high biomass in cool climates, Miscanthus is especially suitable for growing in the temperate regions of the world ( Beale & Long, 1995; Beale , 1996; Naidu , 2003; Wang , 2008 ). Field trials of Miscanthus × giganteus conducted on Illinois cropland in the United States yielded more than 30 tons dry biomass ha −1 ( Heaton , 2008a ). If this yield level is achieved for half of the 14.2 million hectares of the US cropland that is currently set aside for conservation, it can supply feedstocks for making 132 billion liters of ethanol ( Somerville , 2010 ). This could offset 20% of gasoline and 30% of CO 2 emission from petroleum used by the United States in 2008 ( Heaton , 2008a ). Miscanthus × giganteus is a sterile triploid hybrid between diploid Miscanthus sinensis and tetraploid Miscanthus sacchariflorus originated in Japan ( Hodkinson , 2002b ). It was introduced to Europe as an ornamental in the 1930s and was tested as a potential energy crop half a century later ( Long, 1987 ). The hybrid displayed a high photosynthetic rate and high water‐ and nutrient‐use efficiencies, making it a candidate for second‐generation energy crops with high net energy output ( Beale & Long, 1997; Beale , 1999; Clifton‐Brown & Lewandowski, 2000a; Lewandowski , 2000; Lewandowski & Schmidt, 2006; Heaton , 2009 ). However, the productive potential of M . × giganteus is limited by its relatively weak abiotic stress tolerance. As demonstrated in the field trials in northern Europe, crop establishment from small rhizome cuttings suffered from a great loss over the first winter ( Clifton‐Brown & Lewandowski, 2000b ). Subsequent studies showed that samples of the parental species, M. sinensis , from temperate Asia were more resistant to cold and drought stress than M . × giganteus ( Clifton‐Brown , 2001, 2002; Lewandowski , 2003 ), and had higher yield when grown under stressed conditions in Europe ( Farrell , 2006 ). Based on these observations, Miscanthus production models predicted that the improvement of abiotic stress tolerance would be key to realizing the yield potential, and improved crops capable of growing broadly in Europe could meet nearly 12% of the 27 EU states' primary energy needs by 2050 ( Hastings , 2009a, b ). These field trials conducted in the United States and Europe are consistent in suggesting that while Miscanthus has a potential to provide a major source of renewable energy, realization of this potential depends heavily on the ability to utilize land located in cold and dry climates. Furthermore, unlike the United States and EU, many countries in the world do not have extra cropland but have only land with poor soil quality and little irrigation resource for bioenergy production. Thus, sustainable bioenergy production in large scales requires domestication that develops new crops capable of producing sufficiently high biomass on marginal and degraded land with unfavorable climatic conditions ( Jørgensen & Schwarz, 2000; Sang, 2011 ). The first round of plant domestication that began approximately 10 000 years ago provided a stable source of food and laid the foundation of the civilization ( Diamond, 2002 ). Food crop domestication was a process of largely unconscious selection for agricultural traits and could have lasted for centuries to millennia ( Harlan, 1992; Purugganan & Fuller, 2009 ). To effectively mitigate climate change, however, this round of domestication of energy crops needs to be completed within a much shorter period of time, most likely years to decades. Under this time constraint, theoretical frameworks and experimental strategies must be developed to facilitate and accelerate the processes of the new crop domestication. The best way of doing this is to rely on what we have learned from studying the processes and mechanisms of the past crop domestications ( Tang , 2010 ). A sufficient level of genetic variation in a crop species is critical for biotic and abiotic stress resistance and for continuous crop improvement ( Tanksley & McCouch, 1997; Clifton‐Brown , 2008 ). Yet the domestication processes featuring strong artificial selection inevitably led to the reduction of genetic diversity from what existed in the wild progenitors ( Buckler , 2001; Zhu , 2007; Burger , 2008 ). Thus, taking a full advantage of variability and adaptability available in the wild progenitors would have been crucial to the success of crop domestication ( Gepts, 2004; Doebley , 2006 ). Here we report the first study designed to exclusively evaluate variation and adaptation of Miscanthus species potentially serving as the wild progenitors of energy crops. The study was conducted in China, where the highest level of Miscanthus diversity including all high‐biomass species is located ( Chen & Renvoize, 2006; Clifton‐Brown , 2008 ). China possesses more than 100 million hectares of marginal and degraded land concentrated in northern and northwestern regions that could be made available for growing second‐generation energy crops. This holds a potential of producing annually 1 billion tons of Miscanthus biofuel feedstocks, and makes northern and northwestern China a desirable place for experimenting energy crop domestication ( Sang, 2011; Sang & Zhu, 2011 ). This study evaluated three species, including Miscanthus lutarioriparius , the tallest growing Miscanthus species endemic to central China, and M. sinensis and M. sacchariflorus , the parental species of M . × giganteus ( Hodkinson , 2002a; Chen & Renvoize, 2006 ). A total of 93 populations of these species were collected across their distribution ranges in China and grown in three locations, Xilinhot of the Neimenggu Autonomous Region (XN), Qingyang of the Gansu Province (QG), and Jiangxia of the Hubei Province (JH). XN, located in the northern grassland of China, is the coldest and driest of all sites, while JH is the warmest and wettest site. QG is located on the Loess Plateau of northwestern China, one of the most eroded zone of the world. Multiple individuals of a population were sampled for the common garden experiment to evaluate within‐ and between‐species variation. Morphological and physiological traits directly relevant to crop establishment and biomass yield were measured for the assessment of adaptive and productive potentials of the wild populations under distinct climatic conditions. Material and methods Plant material Mature seeds of three Miscanthus species were collected across their distributional ranges in China in October and November 2008. A total of 93 populations were sampled for multiple‐location trials, including 48 populations of M. sacchariflorus , 31 populations of M. sinensis , and 14 populations of M. lutarioriparius ( Fig. 1 ; Table S1). For each population, seeds were collected from 20 to 30 well‐spaced individuals, mixed in a paper bag, air‐dried, and stored at room temperature. 1 Map of collection locations of populations studied in the common garden experiments. Triangle: Miscanthus sacchariflorus ; diamond: Miscanthus sinensis ; circle: Miscanthus lutarioriparius . Red squares indicate three field sites where the common garden experiments were conducted. XN, Xilinhot of the Neimenggu Autonomous Region; QG, Qingyang of the Gansu Province; JH, Jiangxia of the Hubei Province. In March 2009, about 200 seeds from each population were germinated in a Petri dish with wet filter paper at 25 °C. After 1 week, ∼50 germinated seeds of a population were planted in float trays in the greenhouse of the Wuhan Botanical Garden. In May and June, young plants that were 15–20 cm tall were transplanted to three field sites ( Fig. 1 ), including XN, QG, and JH. Transplanting started from south to north, in the sequence of JH, QG, and XN. Climatic data were obtained from the meteorological stations located nearest to the experimental sites. From May 2009 to October 2010, monthly average temperature, precipitation, and sunshine hours were shown in Fig. S1. The rest of the germinated seeds were used for chromosome counting. Chromosome squashes were made using root tips of germinating seeds according to the protocols in Martin (1994) . Multiple‐location trials The experiment used a completely random, two‐way factorial design (species, site). A randomized table was generated for 93 populations each with 15 individuals. At each field site, seedlings were planted 1 m apart in a 60 × 24 m layout according to the order of individuals in the table. Thus, each field site was designed to grow∼1400 individuals with a planting density of 1 m 2 per individual. Seedlings were watered every other day during the first week of planting in 2009. Then watering was stopped at JH, but continued twice a week for 1 and 2 months at drier sites, QG and XN, respectively. In 2010, plants at QG and JH were not watered at all throughout the growing season. At XN where there was a severe summer drought, plants were watered twice in July. Fertilization was not applied during the experiment. Plants that grew to the end of the 2010 season were all robust and thus considered to be established from the point of view of energy crop production. The establishment rate of a population, calculated as the ratio of the number of plants alive at the end of the 2010 growing season to the total number of seedlings planted in 2009, was used to evaluate the ability of the population to establish at the site. The proportion of a population that survived at the end of the 2009 growing season was defined as the seedling survival rate. This was determined by the ratio of survived plants counted in October 2009 to the total number of seedlings initially planted. The overwinter survival rate was used to evaluate the cold tolerance of a population, which was calculated as the ratio of the number of successfully sprouted plants in spring of 2010 to the number of living plants recorded in October 2009. The establishment rate was the product of the seedling survival rate and overwinter survival rate for the majority of the populations, except for those in which a small number of plants died following sprouting in 2010. Several growth traits were measured for every individual grown at each site. Three morphological traits, plant height, tiller diameter, and tiller number, were measured at the end of the 2009 and 2010 growing seasons. Throughout the 2010 growing season, plant height was measured every 2 weeks at QG and JH, and every month at XN. Plant height of an individual was measured from the ground to the top of the tallest tiller. The diameter of this tiller was measure at the position of ∼10 cm aboveground. In 2010, when plant height was measured on the 2‐week schedule, flowering time was recorded. An individual with at least one emerged inflorescence was considered to have flowered. At the end of the growing season in October or November of 2010, the tallest tiller of an individual was removed and brought to the laboratory where it was dried at 65 °C for 48 h and weighed for biomass. Statistical analysis anova s were performed to test the effects of site and species on establishment rates, seedling survival rate, and overwinter survival rate. After a significant effect was detected for the interaction term (site × species), post hoc multiple comparisons of marginal means were carried out with the LSMEANS statement in the GLM procedure. Type‐III sums of squares were used for the calculation of F ‐statistics. Principal component analysis was performed to determine the main influence on the establishment at XN and QG. PCA was conducted using the software spss 13.0 for Windows (SPSS Inc., Chicago, IL, USA). For growth traits (plant height, tiller diameter, tiller number, and flowering time) and biomass, because plants were considered to be established only after the winter of 2009–2010, our analyses were focused on the data collected at the end of the 2010 growing season. Further, because the majority of plants failed to survive over the winter at XN, comparisons were made primarily for plants grown at QG and JH. One population, Sa5, failed to establish at JH. So a total of 92 populations of the three species from both QG and JH were analyzed. These traits were analyzed with nested anova s that included species and sites as fixed effect and populations (nested within species) as a random effect. Means were analyzed with a mixed model and populations (nested within species) as a random effect. Type‐III sums of squares were used to calculate F ‐statistics. Post hoc multiple comparisons of marginal means were performed with the LSMEANS statement in the GLM procedure. To estimate the variation among populations within species at both sites, anova s were used to analyze each trait with populations and sites as fix effects. At QG and JH, logistic curves were used to fit the growth as measured by plant height throughout the 2010 growing season. The growth rates were compared between the two sites by plotting the increase of plant height between two measurements against the time when the later measurement was taken. The flowering rate of a species was calculated as the ratio of flowered plants to the total number of growing individuals of the species at the 2‐week recording time. Considering that a large proportion of plants did not flower at QG and M. lutarioriparius flowered during a very short period of time, the correlation analysis between flowering time and morphological traits was only performed for M. sacchariflorus and M. sinensis at JH. To test correlation between traits or traits and latitudes, Spearman's rank correlation coefficient was estimated using Proc CORR. anova and Spearman's rank correlation were conducted using SAS 9.1 (SAS Institute Inc., Cary, NC, USA). Results Establishment Plants that grew vigorously to the end of the 2010 growing season were considered to be established. The establishment rate of a population is approximately determined by the seedling survival rate in 2009 and the rate of surviving over the winter of 2009–2010. When compared among the three species at the three sites, the establishment rates were significantly different between species and were also significantly influenced by sites and site–species interactions (Table S2). When the species were compared at each site, M. sinensis and M. lutarioriparius had significantly lower establishment rates than M. sacchariflorus at XN, and M. sinensis established at a lower rate than the other two species at QG ( Fig. 2a ). At JH, the establishment rates were not significantly different among the three species. 2 Differences of (a) establishment rates, (b) seedling survival rates, and (c) overwinter survival rates between species and field sites. Different letters indicate significant differences at P =0.05. Error bars indicate one standard error. (d) Principle component analysis indicates that overwinter survival rate contributed primarily to the establishment rate. At XN and QG, the overwinter survival rate appeared to be the primary contributor to the different establishment rates between species ( Fig. 2a–c ). This was supported by a principal component analysis indicating that establishment rates and overwinter survival rates were both more than 98% correlated with the first component ( Fig. 2d ). Thus, the differential establishment of these species at the two northern sites was due primarily to their different abilities of overwinter survival. At relatively warm JH, although the overwinter survival rate of M. sacchariflorus was lower than those of other two species, it apparently was not enough to cause a significantly lower establishment rate of the species. In the coldest site, XN, overwinter survival rates were much lower than those at the other two sites ( Fig. 2c ; Fig. S1). Particularly, only small proportions of M. sinensis and M. lutarioriparius populations were able to survive the cold winter at XN. For M. sinensis , 25 of 31 populations failed to survive, and only two out of 14 M. lutarioriparius populations survived (Fig. S2). Of the eight populations of M. sinensis and M. lutarioriparius survived at XN, only two M. sinensis populations had overwinter survival rates higher than 40% and none of the populations had a survival rate higher than 60%. In comparison, M. sacchariflorus had a much higher overwinter survival rate at XN, with 36 of 48 populations survived, of which 14 and 10 populations had overwinter survival rates higher than 40% and 60%, respectively (Fig. S2). In China, M. sinensis and M. sacchariflorus are distributed across wide latitudes. Correlation analyses indicated that overwinter survival rates at XN had positive correlations with the latitudes of population origin for both species ( Fig. 3a and b ). Together, these results suggest that the northern populations of M. sacchariflorus have the strongest cold tolerance of all studied populations. 3 Correlations between overwinter survival rates and the latitudes of population origin. (a), (c), and (e) Miscanthus sacchariflorus at XN, QG, and JH, respectively; (b), (d), and (f) Miscanthus sinensis at XN, QG, and JH, respectively. XN, Xilinhot of the Neimenggu Autonomous Region; QG, Qingyang of the Gansu Province; JH, Jiangxia of the Hubei Province. The relationship between overwinter survival rates and the latitudes of population origin was also examined at other two sites, QG and JH ( Fig. 3c–f ). A significantly positive correlation was found for M. sinensis at QG, suggesting that the southern populations of M. sinensis had trouble to survive the winter at this middle‐latitude site. At JH, however, the correlation for M. sinensis was negative with a marginal significance. For M. sacchariflorus , negative correlations were found at both sites, indicating that southern populations of this species had higher overwinter survival rates at QG and JH. No significant correlation between any rates and the latitudes of population origin was found for M. lutarioriparius , which was most likely due to the narrow latitudinal distribution of the species. Growth For perennial herbaceous energy crops, the aboveground biomass of Miscanthus is harvested annually as biofuel feedstock. In this study, we measured four growth traits that were relevant to biomass yield. These included plant height, tiller diameter, tiller number, and flowering time. Because of the very low establishment rates of M. sinensis and M. lutarioriparius at XN, we focused our comparisons on data from QG and JH. When the three species were compared at both sites, there was a significant site effect on between‐species differences of plant height and tiller number but not tiller diameter (Table S3). For plant height and tiller diameter, there were significant site–species interactions. When we compared the three morphological traits between species at each site, we found that the majority of the comparisons differed significantly between species, except for plant height between M. sinensis and M. sacchariflorus at QG and tiller number between M. sinensis and M. lutarioriparius at QG ( Fig. 4a–c ). 4 Differences of (a) plant height, (b) tiller diameter, (c) tiller number, and (d) biomass between three species at QG and JH. Different letters indicate significant differences at P =0.05. Error bars indicate 1 SE. QG, Qingyang of the Gansu Province; JH, Jiangxia of the Hubei Province. Within‐population sampling made it possible to evaluate between‐population variation within a species. For all three species at both sites, there was a significant within‐species variation exhibited by almost all traits ( Table 1 ). The only exception was the tiller number of M. sinensis . There was a significant site effect on all traits for each species. A significant site–population interaction effect indicated that three traits for M. sacchariflorus and plant height and tiller diameter for M. sinensis responded differently to sites depending on the population. 1 anova of the effects of sites and populations on growth traits and their variation within species Fixed effect df Plant height Tiller diameter Tiller number Biomass F P ‐value F Ñ ‐value F P ‐value F P ‐value Miscanthus sacchariflorus Population 46 1.97 0.0002 9.11 <0.0001 2.53 <0.0001 5.59 <0.0001 Site 1 38.89 <0.0001 5.69 0.0173 203.36 <0.0001 6.59 0.0104 Site × Population 46 2.21 <0.0001 1.02 0.441 1.83 0.0008 1.77 0.0016 Error 778 Miscanthus sinensis Population 30 7.8 <0.0001 5.69 <0.0001 0.42 0.9972 6.35 <0.0001 Site 1 35.25 <0.0001 65.35 <0.0001 178.12 <0.0001 9.12 0.0027 Site × Population 30 3.47 <0.0001 1.72 0.0116 1.11 0.3214 2.59 <0.0001 Error 446 Miscanthus lutarioriparius Population 13 5.91 <0.0001 3.53 <0.0001 2.6 0.0021 2.93 0.0005 Site 1 36.38 <0.0001 28.59 <0.0001 230.56 <0.0001 3.98 0.0471 Site × Population 13 0.78 0.686 0.81 0.646 1.42 0.1496 0.86 0.5937 Error 257 In 2010, the vast majority of plants flowered at JH, with flowering rates of 75.1%, 99.1%, and 93.4% for M. sacchariflorus, M. sinensis , and M. lutarioriparius , respectively. The flowering rates were much lower at QG, with 59.7%, 66.5%, and 7.2% for M. sacchariflorus, M. sinensis , and M. lutarioriparius , respectively ( Fig. 5 ). At QG, the flowering rates of M. sacchariflorus are positively correlated to the latitudes of population origin ( r =0.343, P =0.017), while the correlation is not significant for M. sinensis ( r =0.147, P =0.455). All three species began to flower earlier at JH than QG; M. sacchariflorus and M. sinensis flowered as early as in June at JH but began to flower in August at QG ( Fig. 5 ). 5 Flowering phenology of three species at (a) QG and (b) JH. Proportions of populations of a species that flowered were recorded every 2 weeks in 2010. QG, Qingyang of the Gansu Province; JH, Jiangxia of the Hubei Province. Considering that a large proportion of plants did not flower at QG, the further analyses of flowering time was conducted only for plants grown at JH. At JH, flowering time was significantly different between species ( P <0.0001). Within species, flowering was significantly different between populations of M. sinensis ( P <0.0001) and M. sacchariflorus ( P <0.0001) but not M. lutarioriparius ( P =0.0635). Switching to reproductive growth slowed down vegetative growth and consequently affected the morphological traits. Indeed, we found significantly positive correlations between flowering time (days from January 1 of 2010) and plant height and tiller diameter for M. sinensis and M. sacchariflorus ( Fig. 6a–d ), meaning that later‐flowered populations tended to have taller and thicker tillers. Flowering time was not correlated with tiller number ( Fig. 6e and f ). No significant correlation was found for any of these traits of M. lutarioriparius whose populations had a relatively narrow distribution (data not shown). 6 Associations between flowering time and morphological traits of the two species at JH. (a), (c), and (e) plant height, tiller diameter, and tiller number for Miscanthus sacchariflorus , respectively; (b), (d), and (f) plant height, tiller diameter, and tiller number for Miscanthus sinensis , respectively. JH, Jiangxia of the Hubei Province. At JH, flowering time had a negative correlation with the latitudes of population origin for M. sinensis ( r =−0.564, P <0.0001), indicating northern populations of the species tended to flower earlier. For M. sacchariflorus , the negative correlation was not significant ( r =−0.239, P =0.104). This may be attributed to a high level of within‐population variation in flowering time of the northern populations of M. sacchariflorus (Fig. S3). In 2010, we monitored growth at QG and JH by measuring plant height every 2 weeks. The results showed that M. lutarioriparius grew much taller than other two species from the beginning to the end of the growing season at both locations ( Fig. 7a ). At JH, plants broke bud dormancy in early March of 2010 and all plants that survived the winter began to grow by the end of March. At the colder location, QG, the break of bud dormancy began early in April and was completed for all survived plants by the end of April. In terms of growth rates estimated by the 2‐week increase in plant height, all three species had peaks of growth immediately following the break of dormancy in the spring ( Fig. 7b and c ). At QG, M. lutarioriparius had another growth peak in early August, which allowed its growth to surpass that at JH. The other two species had late growth peaks in September while the growth rate of M. lutarioriparius bottomed. At JH, only M. sinensis had a late growth peak in September. 7 Plant height monitored during the 2010 growing season. (a) Average plant height of a species calculated every 2 weeks following sprouting at QG and JH. Species abbreviations: Sa, Miscanthus sacchariflorus ; Si, Miscanthus sinensis ; Lu, Miscanthus lutarioriparius . Logistic curves were used to fit the data. (b and c) Growth rates measured by the increase of plant height during 2‐week intervals at QG and JH, respectively. QG, Qingyang of the Gansu Province; JH, Jiangxia of the Hubei Province. Biomass In addition to the growth traits, we measured tiller biomass (thereafter biomass) at QG and JH in order to better project the yield potential of the energy crops. When the three species were compared at both sites, biomass was significantly different between species and the differences were significantly influenced by sites (Table S4). When biomass was compared between species at each site, there was a significant difference for all comparisons except for between M. sacchariflorus and M. sinensis at QG ( Fig. 4d ). When biomass was compared within species at both sites, there was a significant between‐population variation for each species ( Table 1 ). The site effect on the within‐species variation of biomass was significant for M. sacchariflorus and M. sinensis but only marginally significant for M. lutarioriparius . The site–population interaction effect was responsible for biomass variation within M. sacchariflorus and M. sinensis but not M. lutarioriparius . We then analyzed relationships between biomass and the growth traits as well as the latitudes of population origin. At both sites, there were positive correlations between biomass and plant height and tiller diameter (Table S5), reflecting that taller and thicker tillers were heavier. In terms of correlation between biomass and tiller number, there were positive correlations for M. sacchariflorus and M. lutarioriparius at JH. Positive correlation was found between biomass and flowering time for M. sacchariflorus ( r =0.240, P <0.0001) and M. sinensis ( r =0.323, P <0.0001), but not for M. lutarioriparius ( r =0.141, P =0.088). Chromosome counting revealed that two populations of M. sacchariflorus , Sa35 and Sa36, and one population of M. lutarioriparius , Lu02, were tetraploid (2n=76), while the rest of the sampled populations of the three species were diploid (2n=38). This extensive survey of chromosome numbers of Miscanthus species suggested that diploid populations were predominant in China, which contrasts to relatively high frequencies of tetraploid populations of M. sacchariflorus found elsewhere such as in Japan ( Hodkinson , 2002b; Nishiwaki , 2011 ). Discussion Estimating the genetic variability of wild progenitors, especially for adaptive and production‐related traits, is a reasonable starting point of new crop domestication ( Sang, 2011 ). By growing plants in the common garden, one can tease apart genetic from environmental effects on the phenotypic variation of adaptive traits. Regarding between‐species differences in the three morphological traits, of 18 within‐site pair‐wise comparisons made at JH and QG, 16 were significantly different ( Fig. 4a–c ). This indicates that there is a high level of genetic variation underlying the morphological divergences between the species. This source of variation is valuable for crop domestication and can be utilized through selection on hybrids derived from crosses between wild species or between crops domesticated independently from different species, as was documented in the domestication of food crops such as rice ( Sang & Ge, 2007a, b ). In addition to the differentiation between species, variation within species is another source of genetic diversity that can be even more directly incorporated into crops. By sampling within populations of each species, we were able to estimate variation between populations of a species (except the establishment rate for which we could not calculate within population variation). For the three morphological traits evaluated, a great deal of variation was detected within each species ( Table 1 ). Both M. sacchariflorus and M. sinensis are widely distributed, whereas M. lutarioriparius occupies a relatively narrow distributional range and ecological niche. It was recognized as a separate species from M. sacchariflorus based on its thicker and taller tillers and vigorous growth along seasonally flooded river banks and lake shores in central China ( Chen & Renvoize, 2006 ). But in a recent taxonomic revision of the genus, M. lutarioriparius was reduced in rank and treated a subspecies of M. sacchariflorus ( Sun , 2010 ). However, our common garden experiments revealed that there were significant differentiations between these two species at all field sites, suggesting they are genetically diverged in these potentially adaptive traits. Thus, no matter which taxonomic status is more convenient in practice, our study shows that M. lutarioriparius consists of populations adapted to the distinct habitats and differentiated genetically from the populations of M. sacchariflorus . Successful establishment under unfavorable field and climatic conditions is an important step that needs to be achieved at the early stage of energy crop domestication ( Sang, 2011 ). The natural distributions of the Miscanthus species center on eastern and southern China, whereas the marginal and degraded land potentially available for growing energy crops is concentrated in northern and northwestern China ( Sang & Zhu, 2011 ). One of the field sites, XN, is out of the natural distributional ranges of the three species. QG is at the western edge of the distribution of M. sacchariflorus and M. sinensis ( Fig. 1 ). Of the two components of the establishment rate, seedling survival rates during the first growing season were less variable between species and between sites ( Fig. 2b ). At the two northern sites with relatively cold winters, the ability of young plants to survive the first winter is the most serious limiting factor for crop establishment, as was shown in the previous studies in Europe ( Clifton‐Brown & Lewandowski, 2000b ). In this study, the establishment rates were the lowest at XN for all three species, which is clearly attributed to the freezing kill during the cold winter at XN (Fig. S1). M. sacchariflorus was much more tolerant to the very low winter temperature at XN than other two species. Particularly, the northern populations of M. sacchariflorus were the most tolerant, which should be a result of their natural adaptation. This serves as a valuable genetic source for developing energy crops for growing in cold regions. Southern populations of M. sinensis are the least cold‐tolerant and had a significantly lower overwinter survival rate at QG than at JH ( Fig. 2c ). But the overwinter survival rates of other two species, M. sacchariflorus and M. lutarioriparius , were not significantly different between QG and JH. This suggests that in places of the Loess Plateau such as QG, M. sacchariflorus, M. lutarioriparius , and the northern populations of M. sinensis had little trouble to survive through the winter. At JH, the northern populations of M. sacchariflorus had lower overwinter survival rates than the southern populations of the species. This was probably influenced by factors other than cold stress. Northern populations of M. sacchariflorus did not grow as vigorously as southern populations at the stage of establishment, which was reflected in relatively low seedling survival rates of its northern populations at JH (Fig. S4). Following the establishment, achieving higher biomass yield is the next important issue to consider for energy crop domestication. Yield is a complex trait influenced by many factors. Plant architecture and the duration and vigorousness of vegetative growth are of direct relevance to biomass yield. Our analyses indicated that tiller biomass was positively correlated with tiller length (plant height) and diameter that basically determined the tiller size. Biomass was positively correlated with flowering times of M. sacchariflorus and M. sinensis , and so were plant height and tiller diameter. Populations of these two species from higher latitudes flowered earlier at both QG and JH, which considerably slowed down their vegetative growth and subsequently limited the tiller size. Flowering too early is disadvantageous for energy crops because it cuts short the growing season permitted by local precipitation and temperature ( Clifton‐Brown , 2008; Heaton , 2008b ). In their natural habitats in China, M. sacchariflorus and M. sinensis flowered mostly in September and October (data not shown). When they were transplanted to QG and JH, a much wider range of flowering times was observed, from June to October in 2010 ( Fig. 5 ). The earliest flowering plants were among the northern populations of M. sacchariflorus at JH, which could be due to a reaction to warmer temperature and/or different patterns of day length change. The degree of variation indicated that there was a high level of genetic variation controlling flowering time in M. sacchariflorus and M. sinensis , which may be a result of adaptation of the species to a wide range of latitudes ( Clifton‐Brown , 2008; Stewart , 2009 ). This variation can be a complicating factor for crop domestication on one hand, but an opportunity for optimizing the length of crop growing seasons on the other hand. In addition to flowering time, the time of breaking bud dormancy and sprouting is another factor determining the length of the growing season of perennial plants. Although the Miscanthus species flowered earlier at JH than at QG, they sprouted earlier at warmer JH ( Fig. 7a ). At both sites, M. lutarioriparius flowered near the end of the growing season. While the relatively long growing season could have contributed to its high biomass, this was clearly not the only reason. At both locations, M. lutarioriparius had higher growth rates than other two species. The natural populations of M. lutarioriparius are adapted to habitats with a higher water table and grow taller than other two species (Fig. S5), which implies that ample water supply might have been responsible to its higher productivity. However, the common garden experiments showed that M. lutarioriparius grew much bigger than other two species at either location, indicating that the higher productivity of the species is genetically based. It is noteworthy that the plant height of M. lutarioriparius at QG was initially lower than that at JH, but surpassed it from July ( Fig. 7a ). At the end, the average biomass of the species at the drier site, QG, overtook that at JH, which was due primarily to a late growth peak at QG ( Fig. 7b ). It is unclear why M. lutarioriparius had the surge of growth at QG given that both temperature and precipitation were higher at JH and its native habitats alike (Fig. S1). One possibility is that a larger amount of solar radiation at QG than at JH might have played an important role in promoting the growth of the species ( Dohleman , 2009; Dohleman & Long, 2009 ). In any event, this adaptive plasticity makes M. lutarioriparius a valuable genetic resource for developing energy crops with high biomass yield for regions that are colder and drier than its natural habitats. Moreover, the sharp growth peak of M. lutarioriparius in early August was not found in other two species at QG, suggesting that they responded differently to environmental factors promoting growth. The genetic and physiological mechanisms underlying biomass production of the Miscanthus species awaits further investigation. Acknowledgements We thank the Bureau of Yellow River Water and Soil Conservation Control in Xifeng, the Yellow River Committee Xifeng Scientific Experimental Station for Water and Soil Conservation, and the Inner Mongolia Grassland Ecosystem Research Station of the Chinese Academy of Sciences for providing experimental field, technical assistance, and climatic data. Wei Huang and Jinbo Zhang of the Wuhan Botanical Garden assisted field work and data analyses; Zhe Cai, Zhaoshan Wang, and Ruoxun Wei of the Institute of Botany, the Chinese Academy of Sciences helped field collections. The manuscript was improved by valuable comments of anonymous reviewers. The work was supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (KSCX2‐YW‐G‐034) and an open competition grant from the State Key Laboratory of Systematic & Evolutionary Botany at the Institute of Botany, the Chinese Academy of Sciences. References Beale CV , Bint DA , Long SP ( 1996 ) Leaf photosynthesis in the C4‐grass Miscanthus × giganteus , growing in the cool temperate climate of southern England . Journal of Experimental Botany , 47 , 267 – 273 . Beale CV , Long SP ( 1995 ) Can perennial C 4 grasses attain high efficiencies of radiant energy conversion in cool climates? Plant, Cell and Environment , 18 , 641 – 650 . Beale CV , Long SP ( 1997 ) Seasonal dynamics of nutrient accumulation and partitioning in the perennial C 4 ‐grasses Miscanthus × giganteus and Spartina cynosuroides . Biomass and Bioenergy , 12 , 419 – 428 . Beale CV , Morison JIL , Long SP ( 1999 ) Water use efficiency of C 4 perennial grasses in a temperate climate . Agricultural and Forest Meteorology , 96 , 103 – 115 . Buckler ES , Thornsberry JM , Kresovich S ( 2001 ) Molecular diversity, structure and domestication of grasses . Genetics Research , 77 , 213 – 218 . Burger JC , Chapman MA , Burke JM ( 2008 ) Molecular insights into the evolution of crop plants . American Journal of Botany , 95 , 113 – 122 . Chen SL , Renvoize SA ( 2006 ) Miscanthus . In: Flora of China , Vol. 22 (eds Wu ZY , Raven PH , Hong DY ), pp. 581 – 583 . Science Press, Missouri Botanical Garden Press , Beijing, St Louis. Clifton‐Brown JC , Breuer J , Jones MB ( 2007 ) Carbon mitigation by the energy crop Miscanthus . Global Change Biology , 13 , 2296 – 2307 . Clifton‐Brown JC , Chiang YC , Hodkinson TR ( 2008 ) Miscanthus : genetic resources and breeding potential to enhance bioenergy production. In: Genetic Improvement of Bioenergy Crops (ed. Vermerris W ), pp. 273 – 294 . Springer Science , New York. Clifton‐Brown JC , Lewandowski I ( 2000a ) Water use efficiency and biomass partitioning of three different Miscanthus genotypes with limited and unlimited water supply . Annals of Botany , 86 , 191 – 200 . Clifton‐Brown JC , Lewandowski I ( 2000b ) Overwintering problems of newly established Miscanthus plantations can be overcome by identifying genotypes with improved rhizome cold tolerance . New Phytologist , 148 , 287 – 294 . Clifton‐Brown JC , Lewandowski I , Andersson B et al . ( 2001 ) Performance of 15 Miscanthus genotypes at five sites in Europe . Agronomy Journal , 93 , 1013 – 1019 . Clifton‐Brown JC , Lewandowski I , Bangerth F , Jones MB ( 2002 ) Comparative responses to water stress in stay‐green, rapid‐ and slow senescing genotypes of the biomass crop, Miscanthus . New Phytologist , 154 , 335 – 345 . Clifton‐Brown JC , Stampfl PF , Jones MB ( 2004 ) Miscanthus biomass production for energy in Europe and its potential contribution to decreasing fossil fuel carbon emissions . Global Change Biology , 10 , 509 – 518 . Diamond J ( 2002 ) Evolution, consequences and future of plant and animal domestication . Nature , 418 , 700 – 707 . Doebley JF , Gaut BS , Smith BD ( 2006 ) The molecular genetics of crop domestication . Cell , 127 , 1309 – 1321 . Dohleman FG , Heaton EA , Leakey ADB , Long SP ( 2009 ) Does greater leaf‐level photosynthesis contribute to greater solar energy conversion efficiency in Miscanthus when compared to switchgrass? Plant, Cell and Environment , 32 , 1525 – 1537 . Dohleman FG , Long SP ( 2009 ) More productive than maize in the Midwest : how does Miscanthus do it? Plant Physiology , 150 , 2104 – 2115 . Farrell AD , Clifton‐Brown JC , Lewandowski I , Jones MB ( 2006 ) Genotypic variation in cold tolerance influences the yield of Miscanthus . Annals of Applied Biology , 149 , 337 – 345 . Gepts P ( 2004 ) Crop domestication as a long‐term selection experiment . Plant Breeding Reviews , 24 , 1 – 44 . Harlan JR ( 1992 ) Crops and Man , 2nd edn . American Society of Agronomy and Crop Science Society of America , Madison, WI. Hastings A , Clifton‐Brown J , Wattenbach M , Mitchell C , Smith P ( 2009a ) The development of MISCANFOR, a new Miscanthus crop growth model : towards more robust yield predictions under different climatic and soil conditions. Global Change Biology Bioenergy , 1 , 154 – 170 . Hastings A , Clifton‐Brown J , Wattenbach M , Mitchell CP , Stampfl P , Smith P ( 2009b ) Future energy potential of Miscanthus in Europe . Global Change Biology Bioenergy , 1 , 180 – 196 . Heaton EA , Dohleman FG , Long SP ( 2008a ) Meeting US biofuel goals with less land : the potential of Miscanthus. Global Change Biology , 14 , 2000 – 2014 . Heaton EA , Dohleman FG , Long SP ( 2009 ) Seasonal nitrogen dynamics of Miscanthus × giganteus and Panicum virgatum . Global Change Biology Bioenergy , 1 , 297 – 307 . Heaton EA , Flavell RB , Mascia PN , Thomas SR , Dohleman FG , Long SP ( 2008b ) Herbaceous energy crop development : recent progress and future prospects. Current Opinion in Biotechnology , 19 , 202 – 209 . Hodkinson TR , Chase MW , Lledo MD , Salamin N , Renvoize SA ( 2002a ) Phylogenetics of Miscanthus, Saccharum and related genera ( Saccharinae, Andropogoneae, Poaceae ) based on DNA sequences from ITS nuclear ribosomal DNA and plastid trnL intron and trnL‐F intergenic spacers . Journal of Plant Research , 115 , 381 – 392 . Hodkinson TR , Chase MW , Takahashi C , Leitch IJ , Bennett MD , Renvoize SA ( 2002b ) The use of DNA sequencing (ITS and trnL ‐ F ), AFLP, and fluorescent in situ hybridization to study allopolyploid Miscanthus (Poaceae) . American Journal of Botany , 89 , 279 – 286 . Jørgensen U , Schwarz KU ( 2000 ) Why do basic research? A lesson from commercial exploitation of Miscanthus . New Phytologist , 148 , 190 – 193 . Karp A , Shield I ( 2008 ) Bioenergy from plants and the sustainable yield challenge . New Phytologist , 179 , 15 – 32 . Lewandowski I , Clifton‐Brown JC , Andersson B et al . ( 2003 ) Environment and harvest time affects the combustion qualities of Miscanthus genotypes . Agronomy Journal , 95 , 1274 – 1280 . Lewandowski I , Clifton‐Brown JC , Scurlock JMO , Huisman W ( 2000 ) Miscanthus : European experience with a novel energy crop. Biomass and Bioenergy , 19 , 209 – 227 . Lewandowski I , Schmidt U ( 2006 ) Nitrogen, energy and land use efficiencies of Miscanthus , reed canary grass and triticale as determined by the boundary line approach . Agriculture, Ecosystems and Environment , 112 , 335 – 346 . Long SP ( 1987 ) The productivity of C4 cord‐grasses and galingale . In: Energy from Biomass I (eds Grassi G , Zibetta H ), pp. 95 – 99 . Commission of the European Communities/Elsevier Applied Science , London. Martin R , Busch W , Herrmann RG , Wanner G ( 1994 ) Efficient preparation of plant chromosomes for high‐resolution scanning electron microscopy . Chromosome Research , 2 , 411 – 415 . Naidu SL , Moose SP , Al‐Shoaibi AK , Raines CA , Long SP ( 2003 ) Cold tolerance of C4 photosynthesis in Miscanthus × giganteus : adaptation in amounts and sequence of C4 photosynthetic enzymes. Plant Physiology , 132 , 1688 – 1697 . Nishiwaki A , Mizuguti A , Kuwabara S et al . ( 2011 ) Discovery of natural Miscanthus (Poaceae) triploid plants in sympatric populations of Miscanthus sacchariflorus and Miscanthus sinensis in southern Japan . American Journal of Botany , 98 , 154 – 159 . Oliver RJ , Finch JW , Taylor G ( 2009 ) Second generation bioenergy crops and climate change : a review of the effects of elevated atmospheric CO 2 and drought on water use and the implications for yield. Global Change Biology Bioenergy , 1 , 97 – 114 . Purugganan MD , Fuller DQ ( 2009 ) The nature of selection during plant domestication . Nature , 457 , 843 – 848 . Sang T ( 2011 ) Toward the domestication of lignocellulosic energy crops : learning from food crop domestication. Journal of Integrative Plant Biology , 53 , 96 – 104 . Sang T , Ge S ( 2007a ) The puzzle of rice domestication . Journal of Integrative Plant Biology , 49 , 760 – 768 . Sang T , Ge S ( 2007b ) Genetics and phylogenetics of rice domestication . Current Opinion in Genetics and Development , 17 , 533 – 538 . Sang T , Zhu W ( 2011 ) China's bioenergy potential . Global Change Biology Bioenergy , 3 , 79 – 90 . Somerville C , Yongs H , Taylor C , Davis SC , Long SP ( 2010 ) Feedstocks for lignocellulosic biofuels . Science , 329 , 790 – 792 . Stewart JR , Toma Y , Fernández FG , Nishiwaki A , Yamada T , Bollero G ( 2009 ) The ecology and agronomy of Miscanthus sinensis , a species important to bioenergy crop development, in its native range in Japan : a review. Global Change Biology Bioenergy , 1 , 126 – 153 . Sun Q , Lin Q , Yi ZL , Yang ZR , Zhou FS ( 2010 ) A taxonomic revision of Miscanthus s.l . (Poaceae) from China . Botanical Journal of the Linnean Society , 164 , 178 – 220 . Tang H , Sezen U , Paterson AH ( 2010 ) Domestication and plant genomes . Current Opinion in Plant Biology , 13 , 160 – 166 . Tanksley SD , McCouch SR ( 1997 ) Seed banks and molecular maps : unlocking genetic potential from the wild. Science , 277 , 1063 – 1066 . Wang D , Portis AR , Moose SP , Long SP ( 2008 ) Cool C4 photosynthesis : Pyruvate P i dikinase expression and activity corresponds to the exceptional cold tolerance of carbon assimilation in Miscanthus × giganteus . Plant Physiology , 148 , 557 – 567 . Zhu Q , Zheng X , Luo J , Gaut BS , Ge S ( 2007 ) Multilocus analysis of nucleotide variation of Oryza sativa and its wild relatives : severe bottleneck during domestication of rice. Molecular Biology and Evolution , 24 , 857 – 888 . http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png GCB Bioenergy Wiley

Variability and adaptability of Miscanthus species evaluated for energy crop domestication

Download PDF
12 pages

Loading next page...
 
/lp/wiley/variability-and-adaptability-of-miscanthus-species-evaluated-for-uuPPwBMxP7

References (65)

Publisher
Wiley
Copyright
Copyright © 2012 Blackwell Publishing Ltd
ISSN
1757-1693
eISSN
1757-1707
DOI
10.1111/j.1757-1707.2011.01108.x
Publisher site
See Article on Publisher Site

Abstract

Introduction Miscanthus is considered to be a promising candidate for second‐generation energy crops ( Clifton‐Brown , 2004, 2007; Karp & Shield, 2008; Oliver , 2009 ). As a C4 perennial grass capable of producing high biomass in cool climates, Miscanthus is especially suitable for growing in the temperate regions of the world ( Beale & Long, 1995; Beale , 1996; Naidu , 2003; Wang , 2008 ). Field trials of Miscanthus × giganteus conducted on Illinois cropland in the United States yielded more than 30 tons dry biomass ha −1 ( Heaton , 2008a ). If this yield level is achieved for half of the 14.2 million hectares of the US cropland that is currently set aside for conservation, it can supply feedstocks for making 132 billion liters of ethanol ( Somerville , 2010 ). This could offset 20% of gasoline and 30% of CO 2 emission from petroleum used by the United States in 2008 ( Heaton , 2008a ). Miscanthus × giganteus is a sterile triploid hybrid between diploid Miscanthus sinensis and tetraploid Miscanthus sacchariflorus originated in Japan ( Hodkinson , 2002b ). It was introduced to Europe as an ornamental in the 1930s and was tested as a potential energy crop half a century later ( Long, 1987 ). The hybrid displayed a high photosynthetic rate and high water‐ and nutrient‐use efficiencies, making it a candidate for second‐generation energy crops with high net energy output ( Beale & Long, 1997; Beale , 1999; Clifton‐Brown & Lewandowski, 2000a; Lewandowski , 2000; Lewandowski & Schmidt, 2006; Heaton , 2009 ). However, the productive potential of M . × giganteus is limited by its relatively weak abiotic stress tolerance. As demonstrated in the field trials in northern Europe, crop establishment from small rhizome cuttings suffered from a great loss over the first winter ( Clifton‐Brown & Lewandowski, 2000b ). Subsequent studies showed that samples of the parental species, M. sinensis , from temperate Asia were more resistant to cold and drought stress than M . × giganteus ( Clifton‐Brown , 2001, 2002; Lewandowski , 2003 ), and had higher yield when grown under stressed conditions in Europe ( Farrell , 2006 ). Based on these observations, Miscanthus production models predicted that the improvement of abiotic stress tolerance would be key to realizing the yield potential, and improved crops capable of growing broadly in Europe could meet nearly 12% of the 27 EU states' primary energy needs by 2050 ( Hastings , 2009a, b ). These field trials conducted in the United States and Europe are consistent in suggesting that while Miscanthus has a potential to provide a major source of renewable energy, realization of this potential depends heavily on the ability to utilize land located in cold and dry climates. Furthermore, unlike the United States and EU, many countries in the world do not have extra cropland but have only land with poor soil quality and little irrigation resource for bioenergy production. Thus, sustainable bioenergy production in large scales requires domestication that develops new crops capable of producing sufficiently high biomass on marginal and degraded land with unfavorable climatic conditions ( Jørgensen & Schwarz, 2000; Sang, 2011 ). The first round of plant domestication that began approximately 10 000 years ago provided a stable source of food and laid the foundation of the civilization ( Diamond, 2002 ). Food crop domestication was a process of largely unconscious selection for agricultural traits and could have lasted for centuries to millennia ( Harlan, 1992; Purugganan & Fuller, 2009 ). To effectively mitigate climate change, however, this round of domestication of energy crops needs to be completed within a much shorter period of time, most likely years to decades. Under this time constraint, theoretical frameworks and experimental strategies must be developed to facilitate and accelerate the processes of the new crop domestication. The best way of doing this is to rely on what we have learned from studying the processes and mechanisms of the past crop domestications ( Tang , 2010 ). A sufficient level of genetic variation in a crop species is critical for biotic and abiotic stress resistance and for continuous crop improvement ( Tanksley & McCouch, 1997; Clifton‐Brown , 2008 ). Yet the domestication processes featuring strong artificial selection inevitably led to the reduction of genetic diversity from what existed in the wild progenitors ( Buckler , 2001; Zhu , 2007; Burger , 2008 ). Thus, taking a full advantage of variability and adaptability available in the wild progenitors would have been crucial to the success of crop domestication ( Gepts, 2004; Doebley , 2006 ). Here we report the first study designed to exclusively evaluate variation and adaptation of Miscanthus species potentially serving as the wild progenitors of energy crops. The study was conducted in China, where the highest level of Miscanthus diversity including all high‐biomass species is located ( Chen & Renvoize, 2006; Clifton‐Brown , 2008 ). China possesses more than 100 million hectares of marginal and degraded land concentrated in northern and northwestern regions that could be made available for growing second‐generation energy crops. This holds a potential of producing annually 1 billion tons of Miscanthus biofuel feedstocks, and makes northern and northwestern China a desirable place for experimenting energy crop domestication ( Sang, 2011; Sang & Zhu, 2011 ). This study evaluated three species, including Miscanthus lutarioriparius , the tallest growing Miscanthus species endemic to central China, and M. sinensis and M. sacchariflorus , the parental species of M . × giganteus ( Hodkinson , 2002a; Chen & Renvoize, 2006 ). A total of 93 populations of these species were collected across their distribution ranges in China and grown in three locations, Xilinhot of the Neimenggu Autonomous Region (XN), Qingyang of the Gansu Province (QG), and Jiangxia of the Hubei Province (JH). XN, located in the northern grassland of China, is the coldest and driest of all sites, while JH is the warmest and wettest site. QG is located on the Loess Plateau of northwestern China, one of the most eroded zone of the world. Multiple individuals of a population were sampled for the common garden experiment to evaluate within‐ and between‐species variation. Morphological and physiological traits directly relevant to crop establishment and biomass yield were measured for the assessment of adaptive and productive potentials of the wild populations under distinct climatic conditions. Material and methods Plant material Mature seeds of three Miscanthus species were collected across their distributional ranges in China in October and November 2008. A total of 93 populations were sampled for multiple‐location trials, including 48 populations of M. sacchariflorus , 31 populations of M. sinensis , and 14 populations of M. lutarioriparius ( Fig. 1 ; Table S1). For each population, seeds were collected from 20 to 30 well‐spaced individuals, mixed in a paper bag, air‐dried, and stored at room temperature. 1 Map of collection locations of populations studied in the common garden experiments. Triangle: Miscanthus sacchariflorus ; diamond: Miscanthus sinensis ; circle: Miscanthus lutarioriparius . Red squares indicate three field sites where the common garden experiments were conducted. XN, Xilinhot of the Neimenggu Autonomous Region; QG, Qingyang of the Gansu Province; JH, Jiangxia of the Hubei Province. In March 2009, about 200 seeds from each population were germinated in a Petri dish with wet filter paper at 25 °C. After 1 week, ∼50 germinated seeds of a population were planted in float trays in the greenhouse of the Wuhan Botanical Garden. In May and June, young plants that were 15–20 cm tall were transplanted to three field sites ( Fig. 1 ), including XN, QG, and JH. Transplanting started from south to north, in the sequence of JH, QG, and XN. Climatic data were obtained from the meteorological stations located nearest to the experimental sites. From May 2009 to October 2010, monthly average temperature, precipitation, and sunshine hours were shown in Fig. S1. The rest of the germinated seeds were used for chromosome counting. Chromosome squashes were made using root tips of germinating seeds according to the protocols in Martin (1994) . Multiple‐location trials The experiment used a completely random, two‐way factorial design (species, site). A randomized table was generated for 93 populations each with 15 individuals. At each field site, seedlings were planted 1 m apart in a 60 × 24 m layout according to the order of individuals in the table. Thus, each field site was designed to grow∼1400 individuals with a planting density of 1 m 2 per individual. Seedlings were watered every other day during the first week of planting in 2009. Then watering was stopped at JH, but continued twice a week for 1 and 2 months at drier sites, QG and XN, respectively. In 2010, plants at QG and JH were not watered at all throughout the growing season. At XN where there was a severe summer drought, plants were watered twice in July. Fertilization was not applied during the experiment. Plants that grew to the end of the 2010 season were all robust and thus considered to be established from the point of view of energy crop production. The establishment rate of a population, calculated as the ratio of the number of plants alive at the end of the 2010 growing season to the total number of seedlings planted in 2009, was used to evaluate the ability of the population to establish at the site. The proportion of a population that survived at the end of the 2009 growing season was defined as the seedling survival rate. This was determined by the ratio of survived plants counted in October 2009 to the total number of seedlings initially planted. The overwinter survival rate was used to evaluate the cold tolerance of a population, which was calculated as the ratio of the number of successfully sprouted plants in spring of 2010 to the number of living plants recorded in October 2009. The establishment rate was the product of the seedling survival rate and overwinter survival rate for the majority of the populations, except for those in which a small number of plants died following sprouting in 2010. Several growth traits were measured for every individual grown at each site. Three morphological traits, plant height, tiller diameter, and tiller number, were measured at the end of the 2009 and 2010 growing seasons. Throughout the 2010 growing season, plant height was measured every 2 weeks at QG and JH, and every month at XN. Plant height of an individual was measured from the ground to the top of the tallest tiller. The diameter of this tiller was measure at the position of ∼10 cm aboveground. In 2010, when plant height was measured on the 2‐week schedule, flowering time was recorded. An individual with at least one emerged inflorescence was considered to have flowered. At the end of the growing season in October or November of 2010, the tallest tiller of an individual was removed and brought to the laboratory where it was dried at 65 °C for 48 h and weighed for biomass. Statistical analysis anova s were performed to test the effects of site and species on establishment rates, seedling survival rate, and overwinter survival rate. After a significant effect was detected for the interaction term (site × species), post hoc multiple comparisons of marginal means were carried out with the LSMEANS statement in the GLM procedure. Type‐III sums of squares were used for the calculation of F ‐statistics. Principal component analysis was performed to determine the main influence on the establishment at XN and QG. PCA was conducted using the software spss 13.0 for Windows (SPSS Inc., Chicago, IL, USA). For growth traits (plant height, tiller diameter, tiller number, and flowering time) and biomass, because plants were considered to be established only after the winter of 2009–2010, our analyses were focused on the data collected at the end of the 2010 growing season. Further, because the majority of plants failed to survive over the winter at XN, comparisons were made primarily for plants grown at QG and JH. One population, Sa5, failed to establish at JH. So a total of 92 populations of the three species from both QG and JH were analyzed. These traits were analyzed with nested anova s that included species and sites as fixed effect and populations (nested within species) as a random effect. Means were analyzed with a mixed model and populations (nested within species) as a random effect. Type‐III sums of squares were used to calculate F ‐statistics. Post hoc multiple comparisons of marginal means were performed with the LSMEANS statement in the GLM procedure. To estimate the variation among populations within species at both sites, anova s were used to analyze each trait with populations and sites as fix effects. At QG and JH, logistic curves were used to fit the growth as measured by plant height throughout the 2010 growing season. The growth rates were compared between the two sites by plotting the increase of plant height between two measurements against the time when the later measurement was taken. The flowering rate of a species was calculated as the ratio of flowered plants to the total number of growing individuals of the species at the 2‐week recording time. Considering that a large proportion of plants did not flower at QG and M. lutarioriparius flowered during a very short period of time, the correlation analysis between flowering time and morphological traits was only performed for M. sacchariflorus and M. sinensis at JH. To test correlation between traits or traits and latitudes, Spearman's rank correlation coefficient was estimated using Proc CORR. anova and Spearman's rank correlation were conducted using SAS 9.1 (SAS Institute Inc., Cary, NC, USA). Results Establishment Plants that grew vigorously to the end of the 2010 growing season were considered to be established. The establishment rate of a population is approximately determined by the seedling survival rate in 2009 and the rate of surviving over the winter of 2009–2010. When compared among the three species at the three sites, the establishment rates were significantly different between species and were also significantly influenced by sites and site–species interactions (Table S2). When the species were compared at each site, M. sinensis and M. lutarioriparius had significantly lower establishment rates than M. sacchariflorus at XN, and M. sinensis established at a lower rate than the other two species at QG ( Fig. 2a ). At JH, the establishment rates were not significantly different among the three species. 2 Differences of (a) establishment rates, (b) seedling survival rates, and (c) overwinter survival rates between species and field sites. Different letters indicate significant differences at P =0.05. Error bars indicate one standard error. (d) Principle component analysis indicates that overwinter survival rate contributed primarily to the establishment rate. At XN and QG, the overwinter survival rate appeared to be the primary contributor to the different establishment rates between species ( Fig. 2a–c ). This was supported by a principal component analysis indicating that establishment rates and overwinter survival rates were both more than 98% correlated with the first component ( Fig. 2d ). Thus, the differential establishment of these species at the two northern sites was due primarily to their different abilities of overwinter survival. At relatively warm JH, although the overwinter survival rate of M. sacchariflorus was lower than those of other two species, it apparently was not enough to cause a significantly lower establishment rate of the species. In the coldest site, XN, overwinter survival rates were much lower than those at the other two sites ( Fig. 2c ; Fig. S1). Particularly, only small proportions of M. sinensis and M. lutarioriparius populations were able to survive the cold winter at XN. For M. sinensis , 25 of 31 populations failed to survive, and only two out of 14 M. lutarioriparius populations survived (Fig. S2). Of the eight populations of M. sinensis and M. lutarioriparius survived at XN, only two M. sinensis populations had overwinter survival rates higher than 40% and none of the populations had a survival rate higher than 60%. In comparison, M. sacchariflorus had a much higher overwinter survival rate at XN, with 36 of 48 populations survived, of which 14 and 10 populations had overwinter survival rates higher than 40% and 60%, respectively (Fig. S2). In China, M. sinensis and M. sacchariflorus are distributed across wide latitudes. Correlation analyses indicated that overwinter survival rates at XN had positive correlations with the latitudes of population origin for both species ( Fig. 3a and b ). Together, these results suggest that the northern populations of M. sacchariflorus have the strongest cold tolerance of all studied populations. 3 Correlations between overwinter survival rates and the latitudes of population origin. (a), (c), and (e) Miscanthus sacchariflorus at XN, QG, and JH, respectively; (b), (d), and (f) Miscanthus sinensis at XN, QG, and JH, respectively. XN, Xilinhot of the Neimenggu Autonomous Region; QG, Qingyang of the Gansu Province; JH, Jiangxia of the Hubei Province. The relationship between overwinter survival rates and the latitudes of population origin was also examined at other two sites, QG and JH ( Fig. 3c–f ). A significantly positive correlation was found for M. sinensis at QG, suggesting that the southern populations of M. sinensis had trouble to survive the winter at this middle‐latitude site. At JH, however, the correlation for M. sinensis was negative with a marginal significance. For M. sacchariflorus , negative correlations were found at both sites, indicating that southern populations of this species had higher overwinter survival rates at QG and JH. No significant correlation between any rates and the latitudes of population origin was found for M. lutarioriparius , which was most likely due to the narrow latitudinal distribution of the species. Growth For perennial herbaceous energy crops, the aboveground biomass of Miscanthus is harvested annually as biofuel feedstock. In this study, we measured four growth traits that were relevant to biomass yield. These included plant height, tiller diameter, tiller number, and flowering time. Because of the very low establishment rates of M. sinensis and M. lutarioriparius at XN, we focused our comparisons on data from QG and JH. When the three species were compared at both sites, there was a significant site effect on between‐species differences of plant height and tiller number but not tiller diameter (Table S3). For plant height and tiller diameter, there were significant site–species interactions. When we compared the three morphological traits between species at each site, we found that the majority of the comparisons differed significantly between species, except for plant height between M. sinensis and M. sacchariflorus at QG and tiller number between M. sinensis and M. lutarioriparius at QG ( Fig. 4a–c ). 4 Differences of (a) plant height, (b) tiller diameter, (c) tiller number, and (d) biomass between three species at QG and JH. Different letters indicate significant differences at P =0.05. Error bars indicate 1 SE. QG, Qingyang of the Gansu Province; JH, Jiangxia of the Hubei Province. Within‐population sampling made it possible to evaluate between‐population variation within a species. For all three species at both sites, there was a significant within‐species variation exhibited by almost all traits ( Table 1 ). The only exception was the tiller number of M. sinensis . There was a significant site effect on all traits for each species. A significant site–population interaction effect indicated that three traits for M. sacchariflorus and plant height and tiller diameter for M. sinensis responded differently to sites depending on the population. 1 anova of the effects of sites and populations on growth traits and their variation within species Fixed effect df Plant height Tiller diameter Tiller number Biomass F P ‐value F Ñ ‐value F P ‐value F P ‐value Miscanthus sacchariflorus Population 46 1.97 0.0002 9.11 <0.0001 2.53 <0.0001 5.59 <0.0001 Site 1 38.89 <0.0001 5.69 0.0173 203.36 <0.0001 6.59 0.0104 Site × Population 46 2.21 <0.0001 1.02 0.441 1.83 0.0008 1.77 0.0016 Error 778 Miscanthus sinensis Population 30 7.8 <0.0001 5.69 <0.0001 0.42 0.9972 6.35 <0.0001 Site 1 35.25 <0.0001 65.35 <0.0001 178.12 <0.0001 9.12 0.0027 Site × Population 30 3.47 <0.0001 1.72 0.0116 1.11 0.3214 2.59 <0.0001 Error 446 Miscanthus lutarioriparius Population 13 5.91 <0.0001 3.53 <0.0001 2.6 0.0021 2.93 0.0005 Site 1 36.38 <0.0001 28.59 <0.0001 230.56 <0.0001 3.98 0.0471 Site × Population 13 0.78 0.686 0.81 0.646 1.42 0.1496 0.86 0.5937 Error 257 In 2010, the vast majority of plants flowered at JH, with flowering rates of 75.1%, 99.1%, and 93.4% for M. sacchariflorus, M. sinensis , and M. lutarioriparius , respectively. The flowering rates were much lower at QG, with 59.7%, 66.5%, and 7.2% for M. sacchariflorus, M. sinensis , and M. lutarioriparius , respectively ( Fig. 5 ). At QG, the flowering rates of M. sacchariflorus are positively correlated to the latitudes of population origin ( r =0.343, P =0.017), while the correlation is not significant for M. sinensis ( r =0.147, P =0.455). All three species began to flower earlier at JH than QG; M. sacchariflorus and M. sinensis flowered as early as in June at JH but began to flower in August at QG ( Fig. 5 ). 5 Flowering phenology of three species at (a) QG and (b) JH. Proportions of populations of a species that flowered were recorded every 2 weeks in 2010. QG, Qingyang of the Gansu Province; JH, Jiangxia of the Hubei Province. Considering that a large proportion of plants did not flower at QG, the further analyses of flowering time was conducted only for plants grown at JH. At JH, flowering time was significantly different between species ( P <0.0001). Within species, flowering was significantly different between populations of M. sinensis ( P <0.0001) and M. sacchariflorus ( P <0.0001) but not M. lutarioriparius ( P =0.0635). Switching to reproductive growth slowed down vegetative growth and consequently affected the morphological traits. Indeed, we found significantly positive correlations between flowering time (days from January 1 of 2010) and plant height and tiller diameter for M. sinensis and M. sacchariflorus ( Fig. 6a–d ), meaning that later‐flowered populations tended to have taller and thicker tillers. Flowering time was not correlated with tiller number ( Fig. 6e and f ). No significant correlation was found for any of these traits of M. lutarioriparius whose populations had a relatively narrow distribution (data not shown). 6 Associations between flowering time and morphological traits of the two species at JH. (a), (c), and (e) plant height, tiller diameter, and tiller number for Miscanthus sacchariflorus , respectively; (b), (d), and (f) plant height, tiller diameter, and tiller number for Miscanthus sinensis , respectively. JH, Jiangxia of the Hubei Province. At JH, flowering time had a negative correlation with the latitudes of population origin for M. sinensis ( r =−0.564, P <0.0001), indicating northern populations of the species tended to flower earlier. For M. sacchariflorus , the negative correlation was not significant ( r =−0.239, P =0.104). This may be attributed to a high level of within‐population variation in flowering time of the northern populations of M. sacchariflorus (Fig. S3). In 2010, we monitored growth at QG and JH by measuring plant height every 2 weeks. The results showed that M. lutarioriparius grew much taller than other two species from the beginning to the end of the growing season at both locations ( Fig. 7a ). At JH, plants broke bud dormancy in early March of 2010 and all plants that survived the winter began to grow by the end of March. At the colder location, QG, the break of bud dormancy began early in April and was completed for all survived plants by the end of April. In terms of growth rates estimated by the 2‐week increase in plant height, all three species had peaks of growth immediately following the break of dormancy in the spring ( Fig. 7b and c ). At QG, M. lutarioriparius had another growth peak in early August, which allowed its growth to surpass that at JH. The other two species had late growth peaks in September while the growth rate of M. lutarioriparius bottomed. At JH, only M. sinensis had a late growth peak in September. 7 Plant height monitored during the 2010 growing season. (a) Average plant height of a species calculated every 2 weeks following sprouting at QG and JH. Species abbreviations: Sa, Miscanthus sacchariflorus ; Si, Miscanthus sinensis ; Lu, Miscanthus lutarioriparius . Logistic curves were used to fit the data. (b and c) Growth rates measured by the increase of plant height during 2‐week intervals at QG and JH, respectively. QG, Qingyang of the Gansu Province; JH, Jiangxia of the Hubei Province. Biomass In addition to the growth traits, we measured tiller biomass (thereafter biomass) at QG and JH in order to better project the yield potential of the energy crops. When the three species were compared at both sites, biomass was significantly different between species and the differences were significantly influenced by sites (Table S4). When biomass was compared between species at each site, there was a significant difference for all comparisons except for between M. sacchariflorus and M. sinensis at QG ( Fig. 4d ). When biomass was compared within species at both sites, there was a significant between‐population variation for each species ( Table 1 ). The site effect on the within‐species variation of biomass was significant for M. sacchariflorus and M. sinensis but only marginally significant for M. lutarioriparius . The site–population interaction effect was responsible for biomass variation within M. sacchariflorus and M. sinensis but not M. lutarioriparius . We then analyzed relationships between biomass and the growth traits as well as the latitudes of population origin. At both sites, there were positive correlations between biomass and plant height and tiller diameter (Table S5), reflecting that taller and thicker tillers were heavier. In terms of correlation between biomass and tiller number, there were positive correlations for M. sacchariflorus and M. lutarioriparius at JH. Positive correlation was found between biomass and flowering time for M. sacchariflorus ( r =0.240, P <0.0001) and M. sinensis ( r =0.323, P <0.0001), but not for M. lutarioriparius ( r =0.141, P =0.088). Chromosome counting revealed that two populations of M. sacchariflorus , Sa35 and Sa36, and one population of M. lutarioriparius , Lu02, were tetraploid (2n=76), while the rest of the sampled populations of the three species were diploid (2n=38). This extensive survey of chromosome numbers of Miscanthus species suggested that diploid populations were predominant in China, which contrasts to relatively high frequencies of tetraploid populations of M. sacchariflorus found elsewhere such as in Japan ( Hodkinson , 2002b; Nishiwaki , 2011 ). Discussion Estimating the genetic variability of wild progenitors, especially for adaptive and production‐related traits, is a reasonable starting point of new crop domestication ( Sang, 2011 ). By growing plants in the common garden, one can tease apart genetic from environmental effects on the phenotypic variation of adaptive traits. Regarding between‐species differences in the three morphological traits, of 18 within‐site pair‐wise comparisons made at JH and QG, 16 were significantly different ( Fig. 4a–c ). This indicates that there is a high level of genetic variation underlying the morphological divergences between the species. This source of variation is valuable for crop domestication and can be utilized through selection on hybrids derived from crosses between wild species or between crops domesticated independently from different species, as was documented in the domestication of food crops such as rice ( Sang & Ge, 2007a, b ). In addition to the differentiation between species, variation within species is another source of genetic diversity that can be even more directly incorporated into crops. By sampling within populations of each species, we were able to estimate variation between populations of a species (except the establishment rate for which we could not calculate within population variation). For the three morphological traits evaluated, a great deal of variation was detected within each species ( Table 1 ). Both M. sacchariflorus and M. sinensis are widely distributed, whereas M. lutarioriparius occupies a relatively narrow distributional range and ecological niche. It was recognized as a separate species from M. sacchariflorus based on its thicker and taller tillers and vigorous growth along seasonally flooded river banks and lake shores in central China ( Chen & Renvoize, 2006 ). But in a recent taxonomic revision of the genus, M. lutarioriparius was reduced in rank and treated a subspecies of M. sacchariflorus ( Sun , 2010 ). However, our common garden experiments revealed that there were significant differentiations between these two species at all field sites, suggesting they are genetically diverged in these potentially adaptive traits. Thus, no matter which taxonomic status is more convenient in practice, our study shows that M. lutarioriparius consists of populations adapted to the distinct habitats and differentiated genetically from the populations of M. sacchariflorus . Successful establishment under unfavorable field and climatic conditions is an important step that needs to be achieved at the early stage of energy crop domestication ( Sang, 2011 ). The natural distributions of the Miscanthus species center on eastern and southern China, whereas the marginal and degraded land potentially available for growing energy crops is concentrated in northern and northwestern China ( Sang & Zhu, 2011 ). One of the field sites, XN, is out of the natural distributional ranges of the three species. QG is at the western edge of the distribution of M. sacchariflorus and M. sinensis ( Fig. 1 ). Of the two components of the establishment rate, seedling survival rates during the first growing season were less variable between species and between sites ( Fig. 2b ). At the two northern sites with relatively cold winters, the ability of young plants to survive the first winter is the most serious limiting factor for crop establishment, as was shown in the previous studies in Europe ( Clifton‐Brown & Lewandowski, 2000b ). In this study, the establishment rates were the lowest at XN for all three species, which is clearly attributed to the freezing kill during the cold winter at XN (Fig. S1). M. sacchariflorus was much more tolerant to the very low winter temperature at XN than other two species. Particularly, the northern populations of M. sacchariflorus were the most tolerant, which should be a result of their natural adaptation. This serves as a valuable genetic source for developing energy crops for growing in cold regions. Southern populations of M. sinensis are the least cold‐tolerant and had a significantly lower overwinter survival rate at QG than at JH ( Fig. 2c ). But the overwinter survival rates of other two species, M. sacchariflorus and M. lutarioriparius , were not significantly different between QG and JH. This suggests that in places of the Loess Plateau such as QG, M. sacchariflorus, M. lutarioriparius , and the northern populations of M. sinensis had little trouble to survive through the winter. At JH, the northern populations of M. sacchariflorus had lower overwinter survival rates than the southern populations of the species. This was probably influenced by factors other than cold stress. Northern populations of M. sacchariflorus did not grow as vigorously as southern populations at the stage of establishment, which was reflected in relatively low seedling survival rates of its northern populations at JH (Fig. S4). Following the establishment, achieving higher biomass yield is the next important issue to consider for energy crop domestication. Yield is a complex trait influenced by many factors. Plant architecture and the duration and vigorousness of vegetative growth are of direct relevance to biomass yield. Our analyses indicated that tiller biomass was positively correlated with tiller length (plant height) and diameter that basically determined the tiller size. Biomass was positively correlated with flowering times of M. sacchariflorus and M. sinensis , and so were plant height and tiller diameter. Populations of these two species from higher latitudes flowered earlier at both QG and JH, which considerably slowed down their vegetative growth and subsequently limited the tiller size. Flowering too early is disadvantageous for energy crops because it cuts short the growing season permitted by local precipitation and temperature ( Clifton‐Brown , 2008; Heaton , 2008b ). In their natural habitats in China, M. sacchariflorus and M. sinensis flowered mostly in September and October (data not shown). When they were transplanted to QG and JH, a much wider range of flowering times was observed, from June to October in 2010 ( Fig. 5 ). The earliest flowering plants were among the northern populations of M. sacchariflorus at JH, which could be due to a reaction to warmer temperature and/or different patterns of day length change. The degree of variation indicated that there was a high level of genetic variation controlling flowering time in M. sacchariflorus and M. sinensis , which may be a result of adaptation of the species to a wide range of latitudes ( Clifton‐Brown , 2008; Stewart , 2009 ). This variation can be a complicating factor for crop domestication on one hand, but an opportunity for optimizing the length of crop growing seasons on the other hand. In addition to flowering time, the time of breaking bud dormancy and sprouting is another factor determining the length of the growing season of perennial plants. Although the Miscanthus species flowered earlier at JH than at QG, they sprouted earlier at warmer JH ( Fig. 7a ). At both sites, M. lutarioriparius flowered near the end of the growing season. While the relatively long growing season could have contributed to its high biomass, this was clearly not the only reason. At both locations, M. lutarioriparius had higher growth rates than other two species. The natural populations of M. lutarioriparius are adapted to habitats with a higher water table and grow taller than other two species (Fig. S5), which implies that ample water supply might have been responsible to its higher productivity. However, the common garden experiments showed that M. lutarioriparius grew much bigger than other two species at either location, indicating that the higher productivity of the species is genetically based. It is noteworthy that the plant height of M. lutarioriparius at QG was initially lower than that at JH, but surpassed it from July ( Fig. 7a ). At the end, the average biomass of the species at the drier site, QG, overtook that at JH, which was due primarily to a late growth peak at QG ( Fig. 7b ). It is unclear why M. lutarioriparius had the surge of growth at QG given that both temperature and precipitation were higher at JH and its native habitats alike (Fig. S1). One possibility is that a larger amount of solar radiation at QG than at JH might have played an important role in promoting the growth of the species ( Dohleman , 2009; Dohleman & Long, 2009 ). In any event, this adaptive plasticity makes M. lutarioriparius a valuable genetic resource for developing energy crops with high biomass yield for regions that are colder and drier than its natural habitats. Moreover, the sharp growth peak of M. lutarioriparius in early August was not found in other two species at QG, suggesting that they responded differently to environmental factors promoting growth. The genetic and physiological mechanisms underlying biomass production of the Miscanthus species awaits further investigation. Acknowledgements We thank the Bureau of Yellow River Water and Soil Conservation Control in Xifeng, the Yellow River Committee Xifeng Scientific Experimental Station for Water and Soil Conservation, and the Inner Mongolia Grassland Ecosystem Research Station of the Chinese Academy of Sciences for providing experimental field, technical assistance, and climatic data. Wei Huang and Jinbo Zhang of the Wuhan Botanical Garden assisted field work and data analyses; Zhe Cai, Zhaoshan Wang, and Ruoxun Wei of the Institute of Botany, the Chinese Academy of Sciences helped field collections. The manuscript was improved by valuable comments of anonymous reviewers. The work was supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (KSCX2‐YW‐G‐034) and an open competition grant from the State Key Laboratory of Systematic & Evolutionary Botany at the Institute of Botany, the Chinese Academy of Sciences. References Beale CV , Bint DA , Long SP ( 1996 ) Leaf photosynthesis in the C4‐grass Miscanthus × giganteus , growing in the cool temperate climate of southern England . Journal of Experimental Botany , 47 , 267 – 273 . Beale CV , Long SP ( 1995 ) Can perennial C 4 grasses attain high efficiencies of radiant energy conversion in cool climates? Plant, Cell and Environment , 18 , 641 – 650 . Beale CV , Long SP ( 1997 ) Seasonal dynamics of nutrient accumulation and partitioning in the perennial C 4 ‐grasses Miscanthus × giganteus and Spartina cynosuroides . Biomass and Bioenergy , 12 , 419 – 428 . Beale CV , Morison JIL , Long SP ( 1999 ) Water use efficiency of C 4 perennial grasses in a temperate climate . Agricultural and Forest Meteorology , 96 , 103 – 115 . Buckler ES , Thornsberry JM , Kresovich S ( 2001 ) Molecular diversity, structure and domestication of grasses . Genetics Research , 77 , 213 – 218 . Burger JC , Chapman MA , Burke JM ( 2008 ) Molecular insights into the evolution of crop plants . American Journal of Botany , 95 , 113 – 122 . Chen SL , Renvoize SA ( 2006 ) Miscanthus . In: Flora of China , Vol. 22 (eds Wu ZY , Raven PH , Hong DY ), pp. 581 – 583 . Science Press, Missouri Botanical Garden Press , Beijing, St Louis. Clifton‐Brown JC , Breuer J , Jones MB ( 2007 ) Carbon mitigation by the energy crop Miscanthus . Global Change Biology , 13 , 2296 – 2307 . Clifton‐Brown JC , Chiang YC , Hodkinson TR ( 2008 ) Miscanthus : genetic resources and breeding potential to enhance bioenergy production. In: Genetic Improvement of Bioenergy Crops (ed. Vermerris W ), pp. 273 – 294 . Springer Science , New York. Clifton‐Brown JC , Lewandowski I ( 2000a ) Water use efficiency and biomass partitioning of three different Miscanthus genotypes with limited and unlimited water supply . Annals of Botany , 86 , 191 – 200 . Clifton‐Brown JC , Lewandowski I ( 2000b ) Overwintering problems of newly established Miscanthus plantations can be overcome by identifying genotypes with improved rhizome cold tolerance . New Phytologist , 148 , 287 – 294 . Clifton‐Brown JC , Lewandowski I , Andersson B et al . ( 2001 ) Performance of 15 Miscanthus genotypes at five sites in Europe . Agronomy Journal , 93 , 1013 – 1019 . Clifton‐Brown JC , Lewandowski I , Bangerth F , Jones MB ( 2002 ) Comparative responses to water stress in stay‐green, rapid‐ and slow senescing genotypes of the biomass crop, Miscanthus . New Phytologist , 154 , 335 – 345 . Clifton‐Brown JC , Stampfl PF , Jones MB ( 2004 ) Miscanthus biomass production for energy in Europe and its potential contribution to decreasing fossil fuel carbon emissions . Global Change Biology , 10 , 509 – 518 . Diamond J ( 2002 ) Evolution, consequences and future of plant and animal domestication . Nature , 418 , 700 – 707 . Doebley JF , Gaut BS , Smith BD ( 2006 ) The molecular genetics of crop domestication . Cell , 127 , 1309 – 1321 . Dohleman FG , Heaton EA , Leakey ADB , Long SP ( 2009 ) Does greater leaf‐level photosynthesis contribute to greater solar energy conversion efficiency in Miscanthus when compared to switchgrass? Plant, Cell and Environment , 32 , 1525 – 1537 . Dohleman FG , Long SP ( 2009 ) More productive than maize in the Midwest : how does Miscanthus do it? Plant Physiology , 150 , 2104 – 2115 . Farrell AD , Clifton‐Brown JC , Lewandowski I , Jones MB ( 2006 ) Genotypic variation in cold tolerance influences the yield of Miscanthus . Annals of Applied Biology , 149 , 337 – 345 . Gepts P ( 2004 ) Crop domestication as a long‐term selection experiment . Plant Breeding Reviews , 24 , 1 – 44 . Harlan JR ( 1992 ) Crops and Man , 2nd edn . American Society of Agronomy and Crop Science Society of America , Madison, WI. Hastings A , Clifton‐Brown J , Wattenbach M , Mitchell C , Smith P ( 2009a ) The development of MISCANFOR, a new Miscanthus crop growth model : towards more robust yield predictions under different climatic and soil conditions. Global Change Biology Bioenergy , 1 , 154 – 170 . Hastings A , Clifton‐Brown J , Wattenbach M , Mitchell CP , Stampfl P , Smith P ( 2009b ) Future energy potential of Miscanthus in Europe . Global Change Biology Bioenergy , 1 , 180 – 196 . Heaton EA , Dohleman FG , Long SP ( 2008a ) Meeting US biofuel goals with less land : the potential of Miscanthus. Global Change Biology , 14 , 2000 – 2014 . Heaton EA , Dohleman FG , Long SP ( 2009 ) Seasonal nitrogen dynamics of Miscanthus × giganteus and Panicum virgatum . Global Change Biology Bioenergy , 1 , 297 – 307 . Heaton EA , Flavell RB , Mascia PN , Thomas SR , Dohleman FG , Long SP ( 2008b ) Herbaceous energy crop development : recent progress and future prospects. Current Opinion in Biotechnology , 19 , 202 – 209 . Hodkinson TR , Chase MW , Lledo MD , Salamin N , Renvoize SA ( 2002a ) Phylogenetics of Miscanthus, Saccharum and related genera ( Saccharinae, Andropogoneae, Poaceae ) based on DNA sequences from ITS nuclear ribosomal DNA and plastid trnL intron and trnL‐F intergenic spacers . Journal of Plant Research , 115 , 381 – 392 . Hodkinson TR , Chase MW , Takahashi C , Leitch IJ , Bennett MD , Renvoize SA ( 2002b ) The use of DNA sequencing (ITS and trnL ‐ F ), AFLP, and fluorescent in situ hybridization to study allopolyploid Miscanthus (Poaceae) . American Journal of Botany , 89 , 279 – 286 . Jørgensen U , Schwarz KU ( 2000 ) Why do basic research? A lesson from commercial exploitation of Miscanthus . New Phytologist , 148 , 190 – 193 . Karp A , Shield I ( 2008 ) Bioenergy from plants and the sustainable yield challenge . New Phytologist , 179 , 15 – 32 . Lewandowski I , Clifton‐Brown JC , Andersson B et al . ( 2003 ) Environment and harvest time affects the combustion qualities of Miscanthus genotypes . Agronomy Journal , 95 , 1274 – 1280 . Lewandowski I , Clifton‐Brown JC , Scurlock JMO , Huisman W ( 2000 ) Miscanthus : European experience with a novel energy crop. Biomass and Bioenergy , 19 , 209 – 227 . Lewandowski I , Schmidt U ( 2006 ) Nitrogen, energy and land use efficiencies of Miscanthus , reed canary grass and triticale as determined by the boundary line approach . Agriculture, Ecosystems and Environment , 112 , 335 – 346 . Long SP ( 1987 ) The productivity of C4 cord‐grasses and galingale . In: Energy from Biomass I (eds Grassi G , Zibetta H ), pp. 95 – 99 . Commission of the European Communities/Elsevier Applied Science , London. Martin R , Busch W , Herrmann RG , Wanner G ( 1994 ) Efficient preparation of plant chromosomes for high‐resolution scanning electron microscopy . Chromosome Research , 2 , 411 – 415 . Naidu SL , Moose SP , Al‐Shoaibi AK , Raines CA , Long SP ( 2003 ) Cold tolerance of C4 photosynthesis in Miscanthus × giganteus : adaptation in amounts and sequence of C4 photosynthetic enzymes. Plant Physiology , 132 , 1688 – 1697 . Nishiwaki A , Mizuguti A , Kuwabara S et al . ( 2011 ) Discovery of natural Miscanthus (Poaceae) triploid plants in sympatric populations of Miscanthus sacchariflorus and Miscanthus sinensis in southern Japan . American Journal of Botany , 98 , 154 – 159 . Oliver RJ , Finch JW , Taylor G ( 2009 ) Second generation bioenergy crops and climate change : a review of the effects of elevated atmospheric CO 2 and drought on water use and the implications for yield. Global Change Biology Bioenergy , 1 , 97 – 114 . Purugganan MD , Fuller DQ ( 2009 ) The nature of selection during plant domestication . Nature , 457 , 843 – 848 . Sang T ( 2011 ) Toward the domestication of lignocellulosic energy crops : learning from food crop domestication. Journal of Integrative Plant Biology , 53 , 96 – 104 . Sang T , Ge S ( 2007a ) The puzzle of rice domestication . Journal of Integrative Plant Biology , 49 , 760 – 768 . Sang T , Ge S ( 2007b ) Genetics and phylogenetics of rice domestication . Current Opinion in Genetics and Development , 17 , 533 – 538 . Sang T , Zhu W ( 2011 ) China's bioenergy potential . Global Change Biology Bioenergy , 3 , 79 – 90 . Somerville C , Yongs H , Taylor C , Davis SC , Long SP ( 2010 ) Feedstocks for lignocellulosic biofuels . Science , 329 , 790 – 792 . Stewart JR , Toma Y , Fernández FG , Nishiwaki A , Yamada T , Bollero G ( 2009 ) The ecology and agronomy of Miscanthus sinensis , a species important to bioenergy crop development, in its native range in Japan : a review. Global Change Biology Bioenergy , 1 , 126 – 153 . Sun Q , Lin Q , Yi ZL , Yang ZR , Zhou FS ( 2010 ) A taxonomic revision of Miscanthus s.l . (Poaceae) from China . Botanical Journal of the Linnean Society , 164 , 178 – 220 . Tang H , Sezen U , Paterson AH ( 2010 ) Domestication and plant genomes . Current Opinion in Plant Biology , 13 , 160 – 166 . Tanksley SD , McCouch SR ( 1997 ) Seed banks and molecular maps : unlocking genetic potential from the wild. Science , 277 , 1063 – 1066 . Wang D , Portis AR , Moose SP , Long SP ( 2008 ) Cool C4 photosynthesis : Pyruvate P i dikinase expression and activity corresponds to the exceptional cold tolerance of carbon assimilation in Miscanthus × giganteus . Plant Physiology , 148 , 557 – 567 . Zhu Q , Zheng X , Luo J , Gaut BS , Ge S ( 2007 ) Multilocus analysis of nucleotide variation of Oryza sativa and its wild relatives : severe bottleneck during domestication of rice. Molecular Biology and Evolution , 24 , 857 – 888 .

Journal

GCB Bioenergy – Wiley

Published: Jan 1, 2012

There are no references for this article.