Biofumigant activities against <i>Sclerotinia sclerotiorum</i> in <i>Brassica juncea</i> : Natural variation, evaluation, and mechanisms

The development of biological control strategies for disease prevention and management is essential for sustainable agriculture. However, the lack of an effective screening system for biofumigant activities has notably hindered their widespread application. In the present study, we established an effective screening system for assessing biofumigant activities against Sclerotinia sclerotiorum, which was subsequently validated in mustard (Brassica juncea L.) lines. Among the mustard lines examined, the predominant individual glucosinolate (GSLs) identified were 2-propenyl (Allyl) and 3-Butenyl (Butl) GSLs. Notably, Allyl GSLs exhibited nearly double the biofumigant activity compared to Butyl GSLs. Furthermore, the total GSLs demonstrated a stronger correlation with biofumigant activities in these mustard lines, leading to the development of a rapid determination approach utilizing the palladium chloride (PC) method as a primary screening indicator. In response to the biofumigant activities derived from mustard, the mycelial growth of S. sclerotiorum was significantly inhibited. Furthermore, seven hub genes in S. sclerotiorum were identified by RNA sequencing analysis. This study not only established an effective screening system for biofumigant activities against S. sclerotiorum but also explored the underlying mechanisms, which may facilitate the broader promotion and application of biofumigation methods in the future.