Three Sclerotinia species as the cause of white mold on pea in Chongqing and Sichuan of China

Abstract White mold of pea caused by Sclerotinia sclerotiorum is a common disease in China. However, we discovered that the diverse Sclerotinia species could cause white mold on pea plants in Chongqing and Sichuan of China during recent disease surveys. Thus, the objective of this study was to confirm the causal agents from diseased pea plants. The obtained isolates of white mold from Chongqing and Sichuan were identified by morphological characters and molecular characterization to determine the pathogen species, and their pathogenicity was confirmed on pea through completing Koch's postulates. Fungal isolates of Sclerotinia-like were obtained from diseased plants or sclerotia. Based on morphological characteristics and molecular characterization, 30 isolates were identified to three species, six isolates as S. minor, seven as S. sclerotiorum, and 17 as S. trifoliorum. In pathogenicity tests on pea cultivars Zhongwan 4 and Longwan 1, all 30 isolates caused typical symptoms of white mold on the inoculated plants, and the inoculated pathogens were re-isolated from the diseased plants. This study confirmed that white mold of pea was caused by three Sclerotinia species, S. sclerotiorum, S. minor and S. trifoliorum in Chongqing and Sichuan. It is the first report that S. minor and S. trifoliorum cause white mold of pea in Southwest China.