Molecular identity and cultural variability of Athelia rolfsii TMSR-001 and its relative pathogenicity to tomato genotypes

Abstract

Athelia rolfsii (syn. Sclerotium rolfsii), is a destructive soilborne fungal pathogen that causes massive yield losses and plant mortality in tropical countries. In this study, we characterized a Philippine isolate of Athelia rolfsii (TMSR-001) that causes southern blight in tomatoes and evaluated the response of 20 tomato genotypes to southern blight in screen house trials. Athelia rolfsii TMSR-001 was pathogenic to tomato, and its optimal radial growth was recorded in the V8 juice agar medium and oatmeal agar (OA) medium with a 90.00 mm colony growth three days post-incubation (dpi). Sclerotial masses were observed on media, where A. rolfsii (TMSR-001) had poor and moderate mycelial density. The highest number of sclerotial masses was observed in Quarter Strength Potato Dextrose Agar and V8 medium. All tomato genotypes were susceptible to A. rolfsii infection. However, disease severity (% DS) varied significantly (p ≤ 0.05) among the tested tomato genotypes. The USDA 358811 and Marimax showed relatively low susceptibility to the pathogen (DS of 51.85%). The PH 8679 and Cherry were the most susceptible genotypes, with DS of 94.46% and 92.59%, respectively. This study identified Athelia rolfsii TMSR-001 as a tomato southern blight pathogen. The fungus exhibited variable responses to culture media, highlighting the significant role of nutrition in the growth and survival of A. rolfsii. Further selection of disease-resistant tomatoes is warranted. To our knowledge, this is the first screening study conducted on tomato plants in response to the infection of A. rolfsii in the Philippines.