Response of Soybean [ Glycine max (L.) Merr] Genotypes to Red Leaf Blotch Disease in Ethiopia

Red leaf blotch (RLB) poses as a major threat to soybean production globally, and is an immediate threat in Africa, where the disease manifests with considerable severity. Strong resistance in soybean has yet to be identified, therefore, it is imperative that large genetic screens be conducted to provide plant breeders with material for developing cultivars with enhanced resistance or tolerance. To address this need, 360 genetically diverse soybean genotypes were screened in RLB hot spots in Ethiopia on research stations in Metu, Pawe, and Asosa. The planting followed an 18 x 20 alpha lattice design with two replications in the 2023 and 2024 growing seasons and the genotypes were evaluated for their reactions to RLB based on severity scores and the Area Under the Disease Progress Curve (AUDPC). Individual location analyses of variance (ANOVA) revealed highly significant differences among the genotypes for RLB at Metu and Asosa at the R6 growth stage, as well as for the AUDPC values at Metu. Combined analysis of variance revealed highly significant differences among genotypes and genotype-by-location interaction for RLB severity at the R6 growth stage. In this study, none of these genotypes exhibited complete resistance to the disease; however, nearly 10% of the genotypes showed moderate resistance to RLB, which is a promising find that could be useful for breeding programs aimed at improving genetic defense to RLB.