Journal of Plant Diseases and Protection

Singh, M.; Chandel, V.; Hallan, V.; Ram, R.; Zaidi, A.

doi: 10.1007/BF03356278pmid: N/A

Patchouli (Pogostemon cablin) was found infected with a viral disease showing mosaic symptoms on the leaves in the Chand-pur farm at Institute of Himalayan Bioresource Technology campus, Palampur, Himachal Pradesh, India. After ELISA, RT-PCR, IC-PCR and sequencing, the virus was identified as Peanut stripe virus (PStV). Sequence comparison with corresponding sequences of established potyviruses showed 52–93% homol-ogy at nucleotide level. Peanut stripe virus was eliminated from Patchouli plants using meristem tip culture. MS medium amended with benzylaminopurine (2 mg l−1) and indole3-bu-tyric acid (0.05 mg l−1) was used for shoot proliferation and rooting of plants, respectively. More than 88.89% virus-free plants were obtained from 0.2 mm of meristem as shown by indirect ELISA whereas 80.55% virus-free plants were obtained from 0.3 mm size of meristem as indicated by RT-PCR.

Koenig, R.; Holtschulte, B.; Deml, G.; Lüddecke, P.; Schuhmann, S.; Maaß, C.; Richert-Pöggeler, K.

doi: 10.1007/BF03356279pmid: N/A

The genome composition of Beet necrotic yellow vein virus (BNYVV) was analysed in rootlets of field-grown sugar beets belonging to a variety which in spite of carrying the Rz1 resistance gene had developed strong rhizomania symptoms in a small area of France. This area was located in a borderline region between the distribution areas of P type BNYVV on one side and of A and B type BNYVV on the other. All five samples contained P type RNA 5. RNAs 1 to 4 were derived either solely from the A, B or P types or from mixtures of B and P types. It remains to be shown whether or not these RNA reassortments are responsible for the observed resistance breaking. By means of immunosorbent electron microscopy other sugarbeet viruses, i.e. Beet soil-borne virus, Beet virus Q, Beet mosaic virus, Turnip mosaic virus or Beet black scorch virus were not detected in these samples.

Kaemmerer, D.

doi: 10.1007/BF03356280pmid: N/A

With bacterial ring rot affected potato lots must be decontaminated under official control without causing a risk for the dissemination of the disease. Therefore, at the Bavarian State Research Center for Agriculture (LFL) in Freising a research project is conducted to investigate, which characteristics (temperature and retention period) during anaerobic digestion must be given to eliminate Clavibacter michiganensis sub-sp. sepedonicus. Most biogas plants are run at temperatures between 35 and 55°C. Hence, at first a method was developed to study and describe thermosensitivity of the organism in digester material in the relevant temperature range. For this purpose the streptomycin resistant mutant Cms 4053 strep (NCPPB collection, UK) was used. Viable organisms could be exactly quantified after being incubated for ten minutes at different temperatures by combining an enrichment step on growing medium supplemented with streptomycin with real-time PCR (ABI Prism 7000) using TaqMan® probes (TaqMan® BIO-PCR). It could be shown, that the number of colony forming units (cfu) linearily declines between 35 and 55°C with rising temperatures during equal incubation time periods. Every temperature increase of 8°C reduced the number of cfu by a log10 unit.

Klueken, A.; Borgemeister, C.; Hau, B.

doi: 10.1007/BF03356281pmid: N/A

Non-toxigenic strains of Aspergillus flavus (Link) can be used as biological control agents to reduce the contamination of grains such as maize with carcinogenic and immunotoxic aflatoxins. Based on its sclerotial morphology, A. flavus is commonly divided into two types: L strains and S strains. In this study, we applied the non-toxigenic A. flavus L strain BN030D to the soil of five maize fields in Djidja, central Benin, to investigate its effects on the composition of the prevailing fungal communities, on the ratio of A. flavus L strains and S strains, and on the vegetative compatibility of L strains with BN030D. Soil samples were taken before the strain application, and soil and cob samples were taken after BN030D treatment, i.e., at maize harvest. BN030D did not affect the composition of A. flavus, Fusarium spp., Penicillium spp. and A. niger in the soil. There was no significant difference between the number of A. flavus L and S strains in the control and (subsequent) treatment plots before treatment, but significantly more L than S strains in soil and maize after BN030D treatment. About 1% of all L strains isolated from the untreated soil samples were vegetatively compatible to BN030D, confirming the natural presence of the non-toxigenic A. flavus L strain in the study area. Additionally, 59% (soil) and 26% (maize) of all strains isolated from the treated samples belonged to the BN030D vegetative compatibility group. BN030D spread over time and space from the release area into the non-treated buffer area. The implications of these findings for strategies to reduce aflatoxin contamination of maize and the potentials of such a competitive replacement approach for biological control of A. flavus in West Africa are discussed.

Munda, A.; Radisek, S.; Šuštar-Vozlic, J.; Javornik, B.

doi: 10.1007/BF03356282pmid: N/A

Bean anthracnose caused by Colletotrichum lindemuthianum is one of the most destructive diseases in all bean growing areas. AFLP analysis was used to assess genetic variability and relationships among C. lindemuthianum isolates from Slovenia. Isolates were obtained from different common bean growing regions in Slovenia and have previously been characterized as races 23, 55, 103 and 131. AFLP clustering revealed two main groups that did not clearly correspond to race classification based on pathogenicity towards differential common bean cultivars. Local common bean germplasm as well as the set of 12 international differential bean cultivars were evaluated for resistance against the four C. lindemuth-ianum races that occur in Slovenia. None of the 26 local common bean landraces and cultivars was resistant to all four races; however, six genotypes reacted as moderately resistant. Considerably higher level of resistance was recorded among differential common bean cultivars, particularly those derived from the Mesoamerican germplasm. Introgression of some major anthracnose resistance genes from the Mesoamerican germplasm is therefore recommended to develop resistant common bean cultivars for our production system.

Soares, M.; Zanuncio, J.; Leite, G.; Wermelinger, E.; Serrão, J.

doi: 10.1007/BF03356283pmid: N/A

The efficiency of biological control programs with predators depends on knowing defense behaviour of caterpillars to avoid or to reduce predation. The objective was to evaluate whether caterpillars of Thyrinteina arnobia (Lepidoptera: Geometridae) associate different defense behaviours against the predator Podisus distinctus (Heteroptera: Pentatomidae) and to describe them. Adults of this predator were released in three wood screen cages (50 cm × 40 cm × 40 cm) and maintained without food for two days. Caterpillars of T. arnobia of different instars were released inside each cage. Behaviour patterns of these caterpillars were evaluated during 6 consecutive hours. The caterpillars, initially, explored the environment and they assumed camouflage position. They attacked the predators with the jaws. A new defense behaviour was observed in 43% of T. arno bia caterpillars. They hung from silk threads in the cage when upset by the predators. Caterpillars of this herbivore presented different defense behaviour including camouflage, attacking the predator with its jaws and hung from silk threads. This last one is the most efficient defense behaviour against the predator P. distinctus.

doi: 10.1007/BF03356284pmid: N/A