Evaluation of defense gene expression and the virulence factor Cac1 in the interaction between Phaseolus vulgaris and Colletotrichum lindemuthianum

Anthracnose is one of the most limiting diseases in bean cultivation, leading to decreased yield. Mechanisms associated with the induction of the bean defense response during the interaction with Colletotrichum lindemuthianum have been studied, but little is known about the expression of certain virulence factors of this fungus during the infection process. The aim of this study was to evaluate specific molecular determinants triggered during the interaction between C. lindemuthianum and bean plants. For this purpose, qPCR was used to evaluate changes in the expression of the virulence factor Cac1 in two isolates of C. lindemuthianum (Cl(a) and Cl(b)) with contrasting virulence profiles, and to correlate them with the expression of plant defense genes PR1, PR3, PR4, and POD during the early stages post-infection. Molecular ITS analysis showed that both isolates belonged to the Orbiculare clade; however, they clustered differently, a characteristic associated with their distinct virulence profiles. When they were inoculated in bean plants, the Cl(a) isolate was more virulent than the Cl(b) isolate, generating the highest severity value. The Cl(b) isolate induced higher expression of the evaluated plant defense genes than the Cl(a) isolate. However, the virulence factor Cac1 of C. lindemuthianum showed significantly higher expression in Cl(a) than in Cl(b). These results suggest that the Sutagao bean cultivar exhibits a lower expression of defense genes exposed to an isolate of C. lindemuthianum expressing the virulence factor Cac1 in the initial stages of infection.