Pathotypes of Colletotrichum sublineolum in Response to Sorghum Populations with Different Levels of Genetic Diversity in Sete Lagoas‐MG

Sorghum anthracnose is one of the most important and destructive diseases of sorghum. Genetic resistance has been the most efficient strategy to control the disease, but the high variability of the pathogen population in Brazil has resulted in only modest efficacy. Accordingly, we investigated the variability of Colletotrichum sublineolum in response to sorghum populations with three levels of genetic diversity: pure stand, three‐way hybrids and physical mixtures of three‐way hybrids. Six plots of each treatment were planted in different areas and at different dates. A total of 480 isolates, that is 40 single‐conidium isolates per plot, were collected from the field experiment to characterize the variability of the pathogen in each host population. Isolates were inoculated in a greenhouse on a differential line set composed of eight sorghum inbred lines. Our results reveal that the pathogen populations derived from three‐way combinations had higher pathotype diversity than did those derived from pure stand host populations. More complexly, virulent phenotypes were also developed in genetically diverse stands compared to pure stand host populations. The diversification of the host population limits pathogen adaptation, thus resulting in a significantly higher number of pathotypes. The results of this study will improve the management of sorghum anthracnose in the field by helping sorghum breeders maintain disease resistance.