Final Report: Soilborne Pathogens of Sesame

Final Report: Soilborne Pathogens of Sesame

Pathogenicity testing of the soilborne fungi, Corynespora cassiicola and Macrophomina spp. were conducted to determine their ability to cause diseases on two sesame cultivars, using different methods of inoculation. At the same time, glasshouse experiments were conducted to test the resistance responses of sesame cultivars to the root-lesion nematodes, Pratylenchus thornei or P. neglectus, as well as an experiment to test the growth response of sesame to arbuscular mycorrhizal fungi (AMF). The C. cassiicola isolate used was found to be pathogenic to the two sesame varieties, white cv. '6855' and black cv. 'Black Savannah', both as a root rot and target spot causing fungus using different methods of inoculation. The root dipping inoculation with C. cassiicola for root rot disease displayed inconsistencies due to the harmful effect of root wounding which could be misconstrued as effect of the fungal inoculum. Macrophomina phaseolina and M. tecta were found pathogenic, causing charcoal rot in sesame. Moreover, the results of inoculation methods evaluation in this study provided a basis for selecting methods for use in sesame pathology research. Sesame cvs black and white were rated as provisionally resistant to P. neglectus. Insufficient numbers of plants grew to maturity in the P. thornei experiment to assess resistance/ susceptibility. Modifications have since been developed to improve plant germination and establishment for future glasshouse experiments. White sesame cv. '6855' was highly dependent on AMF for plant biomass and height and black sesame cv. “Black Savanah” was moderately dependent. Future experiments with root-lesion nematodes should also investigate the effect of the addition of AMF to the soil to improve plant growth and for effects on nematode reproduction. In addition, on a separate USQ on-going disease scoping sesame trap crop trials with the Broadacre Cropping Initiative project, under the Queensland Department of Agriculture and Fisheries, have shown several soilborne fungal and bacterial species present in representative paddocks across southeast Queensland. Distribution and identities of these microorganisms were determined to identify which ones could potentially affect sesame production.

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