Number of lesions, severity and incubation period of isolates of Corynespora cassiicola in soybean cultivars

ABSTRACT: This study checked the severity and incubation period of isolates of Coryneporacassiicola (C.c) in soybean cultivars, as well verified whether the position of leaflets influences the susceptibility of the plant to target spot. The experiment was conducted in randomized block with 8 isolates of C.c and 8 soybean cultivars factorial scheme, with five repetitions each block. The plants were inoculated with suspension from 2x104 conidia mL-1. The number of lesions per leaf and the incubation period (IP) were evaluated. The ISO 4S isolate caused greater number of lesions in plants. BMX Potência RR, BMX Força RR, and NA 5909 RG had the lowest occurrence of lesions, while the cultivar BMX Elite IPRO showed the highest number of lesions. More lesions were detected in the lower leaf compared to the upper leaf of the plants. The longest IP was observed for ISO 4S in both leaflets, while the lowest IP for ISO 1A, 3A and 2A in the lower leaf, and for ISO 11S and 1S in the median leaf. For cultivars, significant difference in IP was observed only in the lower leaf, with the longest and shortest IP detected for BMX Elite IPRO and BRS 284, respectively. In general, the upper leaf of the plants presented the shortest IP while the lower leaf had the longest IP.