Discovering QTLs related to spot blotch disease in spring wheat ( Triticum aestivum L.) genome

Spot blotch (SB) is a major constraint to wheat ( Triticum aestivum L.) production in South Asia's warmer plains. It is also known as leaf blight, caused by Bipolaris sorokiniana and causes significant yield loss in Eastern Gangetic Plain Zone of India. The aim of this study was to map SB resistance via composite interval mapping (CIM) in the PBW343/IC252874 population, which comprised of 165 doubled haploid lines (DHLs), across two years in India. The area under the disease progress curve (AUDPC) value for each genotype was calculated using the disease severity. The area under the disease progression curve was developed to determine disease progression. The SB severity was measured at the three different plant growth stages viz. GS63, GS69, and GS77. The phenotypic analysis of these lines revealed a constant variance in disease severity, implying that SB resistance is most likely polygenic. The phenotypic data was used to map Quantitative trait loci (QTL) using SSR markers. The presence of quantitative inheritance with transgressive segregation for SB resistance in the population was also revealed. The QTLs were discovered on 12 chromosomes i.e. 1B, 1D, 2A, 2B, 2D, 3B, 4A, 4D, 5A, 5B, 6A, and 7A. We have also found two consistent QTLs on the chromosomes, 2B and 5B with the average percentage variance explained (PVE) of 17.9% and 19.9% respectively. These current finding reveals new genomic regions linked to spot blotch disease, which could be useful for wheat breeding strategies considering disease resistance with further validation.