Unraveling the Genetic Architecture of Sclerotinia Basal Stalk Rot Resistance in Sunflower through Genome-Wide Association Mapping

Abstract Text: Sclerotinia basal stalk rot (BSR), caused by the necrotrophic fungal pathogen Sclerotinia sclerotiorum, poses a major threat to global sunflower production. Resistance to BSR is quantitatively inherited and genetically complex. To understand the genetic basis of resistance, a genome-wide association study (GWAS) was conducted using two S. sclerotiorum isolates of varying aggressiveness (NEB 274 and BN 166) on a diverse panel of 287 sunflower genotypes. BSR response was evaluated using two disease descriptors: mean days to death (MD) and area under the mortality curve (AUMC). High-density genotyping from whole-genome re-sequencing identified 3.2 million single nucleotide polymorphisms (SNPs) for association analysis. For isolate BN 166, seven QTLs were associated with AUMC and six with MD, while for isolate NEB 274, five common QTLs were linked to both traits, with an additional three QTLs specific to AUMC and one to MD. Candidate genes underlying these loci include Glutathione S-transferase T3, Disease resistance protein RPV1, and NBS-LRR proteins, suggesting potential mechanisms for resistance. These findings provide valuable genetic markers for marker-assisted selection and offer new insights into breeding sunflowers with enhanced resistance to BSR.