Effective selection of soybean cultivars to wildfire disease pathogen Pseudomonas amygdali pv. tabaci

Wildfire, caused by Pseudomonas amygdali pv. tabaci is one of the most destructive bacterial diseases and was recognized as a disease of soybean in 1943. Wildfire has been seen a steady increase in the incidence and prevalence on some cultivars of soybean in Korea by climatic changes but there is little information on effective control measures for wildfire or soybean varieties showing complete resistance to the disease. In this study, the efficient and reliable screening method to evaluate soybean genotype for resistance to P. amygdali pv. tabaci in field had been developed. In order to determine the host resistance of the soybean cultivar against P. amygdali pv. tabaci, development of symptom by infiltration inoculation was evaluated. Significant differences between susceptible plants and resistant plants were observed through these assays. Based on these results, 'Shinpaldal2', 'Daepung' are resistant to wildfire compared to 'Hwangeum', 'Taekwang'. The optimum temperature of this pathogen was between 20-25°C and when the pathogen was in the optimum temperature, the responses of susceptible or resistant cultivar were dramatically different. Prior to initiation of resistance breeding of soybean wildfire, it is imperative to set uniform resistance screening techniques. The obtained results can be effectively used to enhance the selection of wildfire resistance as well as directly applied in resistant soybean development. Resistant lines identified through this assay could be directly used in soybean breeding programs for wildfire resistance.