The flower is the primary infection site of Sclerotinia sclerotiorum in the disease cycle of Sclerotinia white mold in rapeseed. Therefore, designing and breeding floral resistance cultivars would be an efficient strategy to control this disease. Nevertheless, a standardized system for evaluating floral resistance to this pathogen is currently lacking. To resolve this gap, we developed a mycelial suspension inoculation method for rapeseed flowers under both greenhouse and field conditions. Furthermore, we established a disease severity rating system for individual flowers and a floral resistance rating system for germplasms through field assays for 35 core rapeseed germplasms. The practicality and effectiveness of the floral resistance evaluation system were further validated in both greenhouse and field. With this system, we identified R4879 (Hungry Gap) as a flower-resistant germplasm in two-year field trials. Taken together, this study provides a methodological foundation for evaluation of rapeseed floral resistance to S. sclerotiorum, thereby supporting breeding for floral resistant rapeseed varieties.
Li et al. (Sun,) studied this question.