journal article
LitStream Collection
Home
Hammond, J. J.; Gardner, C. O.
doi: 10.2135/cropsci1974.0011183X001400010002xpmid: N/A
A general model for the analysis of variety cross diallels was modified for use when the populations represent different cycles of selection from one parent variety. The a and d parameters in the improved populations are functions of a and d in the parent variety assuming negligible mutation effects. The modified model permits the simultaneous estimation of a polynomial regression in a and in d. The regression equation in homozygous effects (a) is a direct measure of weighted average change in gene frequency, and the equation in heterozygous effects (d) is a measure of the approach to fixation of the favorable alleles. If favorable genes are dominant, the first derivative of the equation in heterozygous effects evaluated at zero gives the cycle at which the weighted average gene frequency will be 0.5.
Busbice, T. H.; Hunt, O. J.; Elgin, J. H.; Peaden, R. N.
doi: 10.2135/cropsci1974.0011183X001400010003xpmid: N/A
Selection for forage yield based on polycross‐ and selfprogeny performance was practiced on two broadbased alfalfa (Medicago sativa L.) populations by selecting the best 10% as parents for experimental synthetic varieties. Random samples of 60 plants from populations A and B were assessed for breeding value to compare the efficiencies of the polycross‐ and the self‐progeny test methods. The best six plants from each population and from each test method were selected as parents for synthetic varieties. The Syn 2 generations of several experimental synthetics were evaluated near Raleigh, N. C.; Reno, Nevada; and Prosser, Washington. Selection based on both methods of progeny testing was ineffective in increasing yield. The study indicated the importance of genotype ✕ environment interactions on selection experiments.
doi: 10.2135/cropsci1974.0011183X001400010004xpmid: N/A
Symbiotic nitrogen fixation of two field grown soybean [Glycine max (L.) Merr.] varieties, ‘Chippewa 64’ and ‘Clay,’ was measured at 7 to 10 day intervals starting at flowering, using the acetylene reduction assay. At he end of flowering, treatments were applied which were designed to alter the relationship between the photosynthetic source and sink components in the plants. The treatments were supplemental light, 25% shade, 50% depodding, 60% defoliation, and control.
Lawn, R. J.; Fischer, K. S.; Brun, William A.
doi: 10.2135/cropsci1974.0011183X001400010005xpmid: N/A
Reciprocal intervarietal grafts were made in all root: shoot combinations using seedlings of eight soybean (Glycine max (L.) Merr.) genotypes, grown in sandfilled pots in the greenhouse. After grafting, the plants were inoculated with Rhizobium japonicum (USDA strain #138) and watered with a low‐nitrogen nutrient solution. Two replicate plants of each root:shoot combination were sampled at each of four times, 28, 38, 50, and 58 days after grafting, for photosynthetic rate of leaves; leaf area, shoot and root dry weight; and number, fresh weight, and acetylene reduction activity of nodules.
doi: 10.2135/cropsci1974.0011183X001400010006xpmid: N/A
Two field experiments were conducted to determine the effect of 1) grafting onto root genotypes with different nitrogen fixation rates, and 2) supplemental nitrogen applied at the time of declining nodule activity (end of flowering), on nodulation, seed yield, and protein yield of ‘Chippewa 64’ and ‘Clay’ soybeans (Glycine max (L.) Merr.). The experiments were conducted in situations of low available soil nitrogen to ensure a strong reliance on symbiotic nitrogen fixation. In the first study, seedling shoots of both varieties were grafted onto four roofstocks: ‘Wayne’, ‘Altona’, Chippewa 64 and Clay.
Nelson, C. J.; Asay, K. H.; Horst, G. L.; Hilderbrand, E. S.
doi: 10.2135/cropsci1974.0011183X001400010007xpmid: N/A
A system for rapid measurement of net carbon exchange (NCE) by leaves of clonal lines of forage grasses growing in the fidd has been developed. Air‐sealed leaf chambers of laminated construction connected to a manifold permit the determination of the average NCE of several leaves measured simultaneously. With 4 replications and more than 10 genotypes, the average NCE from 6 individual leaf measurements per plot was adequate to detect statistical differences of 2.0 mg dm−2 hour−1 between 2 genotypes with 83% power. Two units of six leaf chambers, each operating simultaneously, are monitored by one infrared CO2 analyzer, allowing the average NCE rates of 20 plots/hour to be accurately measured. The system is reliable, rapid, relatively simple, and uses intact leaves for field measurement. The technique is being used to determine genetic variability, heritability, and potential use of NCEin a tall fescue (Festuca arundinacea Schreb.) breeding program.
Pulgar, Claudio E.; Laude, Horton M.
doi: 10.2135/cropsci1974.0011183X001400010008xpmid: N/A
The extent and persistence of growth depression in alfalfa (Medicago sativa L.) following heat stress was established under controlled conditions by comparing stressed with unstressed plants of the same clone. Temperatures were used that simulated the periodic heat extremes of the field. Significant reduction in number and length of shoots in the regrowth was obtained within 7 days of stress. The period of depressed growth was extended as the intensity of stress was increased either by elevating temperature or lengthening exposure time. Measurable reduction in shoot numbers and size persisted up to 6 weeks following a stress which produced no visible evidence of tissue mortality.
doi: 10.2135/cropsci1974.0011183X001400010009xpmid: N/A
Female fertility was determined in greenhouse and field‐grown chemical male‐sterile lines (C‐lines) of wheat (Triticum aestivum L.) following application of 2‐chloroethylphosphonic acid (Ethephon) as a gametocide. In greenhouse studies, number of seed per spike and percent of F1 hybrid seed produced on C‐lines did not differ significantly from male‐sterile B‐lines following hand pollination for both lines. At pre‐, early, mid‐, and late boot stages, all rates of Ethephon resulted in 87% or more F1 seed. Progeny from seed set on plants treated in the field in 1970 and 1971 showed that the percent outcrossing ranged from 5 to 100%. Based on the percent hybrid seed obtained, the optimumst ages for field application in ‘Nugaines’ wheat were pre, early, and midboot at chemical dosages of 1,500 to 3,000 ppm. Sensitivity to Ethephon treatment appeared to be greater in the greenhouse than in the field. Under field conditions significant increases in seed set on nonbagged spikes over that of bagged spikes for field grown C‐lines were shown. This observation coupled with the significant occurrence of hybrid seed produced on C‐lines grown in the field or in the greenhouse indicate that female fertility was high following chemical sterilization by Ethephon
doi: 10.2135/cropsci1974.0011183X001400010010xpmid: N/A
Several morphological traits were examined in smooth bromegrass (Bromus inermis Leyss.) Significant differences were found among genotypes for leaf length, leaf width, culm diameter, plant height, and plant color. General combining ability was significant at the 1% level for leaf width, culm diameter, and plant color. Specific combining ability was significant at the 5% level for leaf length and plant height.
Showing 1 to 10 of 55 Articles