Field response and genetic variability of elite spring bread wheat (Triticum aestivum L.) genotypes for septoria tritici blotch under natural infection in Northwest Ethiopia

Fungal diseases cause significant yield loss to wheat production. Septoria tritici blotch (STB), caused by the ascomycete fungus Zymoseptoria trtici, is one of the major fungal diseases affecting wheat production worldwide. In Ethiopia, STB is a severe problem that causes significant yield loss in high and mid-altitude wheat-growing areas. The use of resistant varieties is one of the sustainable disease management strategies, particularly for resource-poor farmers in developing countries. Two hundred and fifty bread wheat genotypes were evaluated to identify septoria tritici resistant genotypes and estimate the extent of genetic variability for resistance to STB and other economically important traits using alpha lattice design under natural infestation in two STB hotspot environments. Analysis of variance revealed highly significant differences among genotypes, environment, and genotype × environment interaction for all traits measured. The genetic coefficient of variance was lower than the phenotypic coefficient of variance for all traits studied, and both test environments showed the influence of the environment on trait expression. High and moderate heritability values were observed for the septoria disease severity parameters, indicating that the STB resistance trait was less influenced by the environment. The days to heading and plant height were inversely correlated with disease severity. This suggests that genotypes with tall plant height and long maturity period could be resistant to septoria tritici blotch through escape mechanisms. Four of the genotypes, namely, G-215, G-255, G-257, and G-258, were found to be resistant across all locations. These and other promising genotypes will be used in future breeding programmes to select or develop high-yielding and STB-resistant bread wheat genotypes that can be deployed in septoria tritici blotch-prone areas. Highly susceptible genotypes will also be used as controls for STB resistance breeding programmes.