Two independent dominant resistance genes confer resistance to spot blotch in wheat.

Bipolaris sorokiniana-induced spot blotch constitutes a major wheat disease in warm, humid production regions globally. Elucidating its genetic control is essential for breeding cultivars that mitigate yield and quality losses. We evaluated F2 and F2:3 generations from a WE35 × S2199 cross for resistance phenotypes. Genetic analysis revealed that resistance was controlled by two independent dominant genes: the previously identified Sb3 and a novel resistance gene designated SbWE35. Bulked segregant RNA-Seq (BSR-Seq) analysis using a segregating population from a cross between WE35 and a spot blotch susceptible line 621-18-3 mapped SbWE35 to chromosome 4BL. Fine mapping delimited SbWE35 to a 0.07 cM interval between markers YK12918 and YK13104 corresponding to 1.08 Mb in the Chinese Spring reference genome. Comparative genetic mapping revealed substantial overlap between the SbWE35 and Sb4 intervals, suggesting that SbWE35 and Sb4 may represent the same genetic locus, although formal allelism tests are required for confirmation. KEY MESSAGE : We identifiedSbWE35, a wheat spot blotch resistance gene, and demonstrated that resistance to spot blotch is controlled by two independent dominant genes,Sb3andSbWE35.