Characterization of diversity in Colletotrichum lindemuthianum in Parana, Brazil, suggest breeding strategies for anthracnose resistance in common bean

Anthracnose is a major disease of common bean in Parana and other Brazilian states. The changing virulence of Colletotrichum lindemuthianum complicates breeding for anthracnose resistance. An objective of this study was to characterize the virulence and genetic diversity of 19 isolates of C. lindemuthianum from Parana. Virulence was characterized by inoculating each isolate on an international set of 12 common bean differential cultivars. Thirteen virulent races were identified. This is the first report of races 24 and 345 in Parana. Race 24 has also been reported in Mato Grosso. Race 345 is new to Parana and Brazil and both races are new to the world. This virulence diversity confirmed the extensive and changing nature of C. lindemuthianum in Parana. To study the genetic diversity, we sequenced the internal transcribed spacer of the ribosomal DNA of the 19 isolates. This revealed a high level of genetic polymorphism among the isolates. The resistance index (RI) of each of the 12 differential cultivars to the 13 races uncovered in this study was very similar to the RI of the same differential cultivars to the 63 races reported in Parana from 1994 to 2017. The Middle American and Andean differential cultivars that were resistant to the 13 races were also resistant to the 63 races. These results suggest that combining certain anthracnose resistance genes of Middle American origin and Andean origin is an effective strategy to manage the virulence diversity of C. lindemuthianum in Parana and in similar areas of Brazil and other countries.