Unveiling the mechanistic regulation of host genetic resistance in oilseed brassica against Sclerotinia sclerotiorum: A comprehensive study across developmental growth stages

Abstract

Sclerotinia sclerotiorum, causing Sclerotinia stem rot, poses a significant threat to oilseed Brassica crops, necessitating 
the identication of resistant genotypes. Previous studies often used single pathogen isolates or plant-developmental 
stages to identify resistance. Our recent study revealed diverse resistance mechanisms in Brassicaceae genotypes 
against S. sclerotiorum, emphasizing the need for understanding these mechanisms. We evaluated ten Brassicaceae 
genotypes at four plant developmental stages against six diverse S. sclerotiorum isolates from India, assessing both 
structural and physiological resistance traits. Results showed significant (P ≤ 0.05) effects of host genotype, 
developmental stage, pathogen isolate, and their interactions on resistance components. S. alba SA1 consistently 
displayed resistance, making it an ideal candidate for resistance breeding. Other genotypes exhibited age and isolate 
dependency, and resistance varied among developmental stages. The study identied nine suitable host genotypes as 
differentials for characterizing S. sclerotiorum pathotypes and delineated six distinct pathotypes. Stem physical strength 
and physio-biochemical attributes were genotype-specic and dependent on plant developmental stage. S. alba 
genotypes exhibited higher stem physical strength, while other genotypes displayed superior physio-biochemical traits. 
Disease pressure was negatively correlated with stem lignin content, indicating its role in durable resistance, while a 
positive correlation was observed between disease severity and total soluble sugar. The study emphasizes the 
importance of combining structural and physiological resistance for developing cultivars with durable resistance to S. 
sclerotiorum in oilseed Brassica.