Discovering chromosomal regions related to spot blotch disease in wheat (Triticum aestivum L.) by QTL analysis

Spot blotch (SB) is a major constraint to wheat ( Triticum aestivum L.) production in South Asia's warmer plains. SB, also known as leaf blight, is caused by Bipolaris sorokiniana and causes significant yield losses in India's Eastern Gangetic Plain Zone. 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 phenotypic analysis of these lines revealed a constant variance in disease severity, implying that SB resistance is most likely polygenic. DHLs' phenotypic data was also used to map QTLs 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. A new QTL was detected on chromosome 4D being linked to SB in both years. We have also found two consistent QTLs on the chromosomes, 2B and 5B with the average PVE of 17.9% and 19.9% respectively. These findings reveal new genomic areas linked to spot blotch disease, which could be used in disease resistance breeding strategies in wheat advancement with further validation.