Pathogenic Variability and Race Structure of Colletotrichum lindemuthianum Isolates From Common Bean in Ethiopia

Bean anthracnose, caused by Colletothricum lindemuthianum, poses a significant threat to common bean production in Ethiopia. The objective of this study was to determine the pathogenic variability and race structure and distribution of bean anthracnose in four selected zones (Metekel, Sidama, Wolaita and Halaba) of Ethiopia. Field surveys were conducted at 5–7 km intervals, focusing on diseased plant parts of common bean. The severity, incidence and prevalence of bean anthracnose were assessed and determined, and a total of 74 bean anthracnose isolates were obtained for further analysis. The isolates were tested on the 12 standard differential cultivars. The results revealed a wide range of pathogenic variability, with severity ranging from 0% to 24.1%, incidence from 0% to 87% and prevalence from 0% to 100%. The 74 isolates were classified into 32 distinct pathogenic races with 20 of them being newly identified races specific to Ethiopia. Dibate district had the highest number of races (12), whereas Sodo_Zuria and Borecha district had only one. Race 128 was widely distributed, and race 3770 was the most virulent, infecting 8 of the 12 differential cultivars. Around 14% of the isolates were virulent to one differential cultivar, whereas 4.1% to eight cultivars. These findings have important implications for developing resistant cultivars by deploying resistance genes into an improved cultivar and ensuring sustainable common bean production in Ethiopia and other related countries.