Email: ngmmahi.singh865@gmail.com

Spot blotch disease (caused by Bipolaris sorokiniana) results in significant yield loss in wheat. To identify the genetic regulators for spot blotch resistance, we evaluated 1500 elite wheat lines in two diverse environments. A highly significant negative association was observed between the area under the disease progress curve (AUDPC) and stay-green traits, indicating that the disease drastically affects the total greenness of the plant.

Additionally, a negative association was observed between the AUDPC and days to heading (DH), and a positive association between stay green traits and DH, underscoring the substantial impact of DH on disease dynamics.

Further, we performed genome-wide association mapping using three different GWAS models: MLM, FarmCPU, and BLINK, which identified a total of 180 SNPs associated with the area under the disease progress curve (AUDPC) and 148 SNPs with stay-green traits.

There were 7 marker-trait associations (MTAs) that remained stable across environments for AUDPC, and out of those, 3 MTAs (3B_6127880, 5B_546704556, and 5B_546132836) were shared between AUDPC and other stay-green traits. However, a separate supporting GWAS in genotypes with similar DH, showed only MTA 3B_6127880, stable for AUDPC.

Time course analysis of the candidate genes associated with these MTAs in susceptible and resistant genotypes under spot blotch conditions prioritized genes which are expressed differentially and associated with early defense signaling and late defense response to spot blotch. Notably two CGs TraesCS3B02G014400 (coding for expansin) and TraesCS3B02G015000 (uncharacterized protein) were induced significantly against SB disease.

These findings can enable efforts to selectively breed genotypes with favorable alleles, superior haplotypes or prioritized candidate genes for improving resistance against spot blotch in wheat.