Evaluation of Virulence to Adlays of Korean Isolates of Bipolaris coicis Using a Disease Rating Scale

Abstract

The virulence of 33 isolates of Bipolaris coicis from diverse geographic origins in Korea was evaluated on six adlay cultivars or lines under controlled environmental conditions. To evaluate infection levels of B. coicis isolates in adlay plants, a 10-class disease rating scale was developed based on the qualitative and quantitative differences of lesions on adlay leaves infected. There were significant differences in virulence among isolates of B. coicis, although the differences were quantitative rather than qualitative. Significant differences also were observed among cultivar-isolate interactions in the analysis of variance. All isolates of B. coicis, except KG-9515, were pathogenic on adlay plants. BC-20136, the most virulent isolate, was capable of causing highly susceptible reactions on the adlay cultivars or lines. Significant differences in levels of resistance were found among six adlay cultivars or lines tested. The disease rating scale may be a reliable criterion to evaluate a large number of adlays for resistance to leaf blight or B. coicis isolates for virulence to adlays.