Detection and mapping of gm13, a QTL governing recessive resistance to rice gall midge

The Asian rice gall midge (RGM, Orseolia oryzae Wood-Mason) is a major devastating insect pest of rice, causing continuous damage from seedling to tillering stage. Its larvae invade the basal meristematic tissues of rice shoots, secreting effectors that induce the formation of characteristic hollow, tube-like structures known as 'silver-shoot', which inhibits panicle development. Deploying resistant cultivars harboring RGM resistance genes remains the most effective, environment-friendly, and sustainable management strategy, yet the discovery of novel resistance loci remains critical. We found that rice variety NY74 employs a combination of antixenotic and antibiotic defenses against RGM, without a hypersensitive response during the first 16 days of infestation. Genetic segregation analysis revealed that resistance in NY74 is governed by a single recessive locus, designated as gm13. Initial mapping using bulked segregant analysis (BSA) localized gm13 to chromosome 8L. The identified quantitative trait locus (QTL) individually explained 41.7 % of the phenotypic variation, with likelihood of odd (LOD) score 14.3. Subsequently, high-resolution linkage analysis segregating progenies further refined the locus to an 82 kb interval between 18.33 Mb and 18.41 Mb. Functional annotation of the candidate region identified a resistance gene homolog, gene1, as the most promising candidate gene, characterized by a leucine-rich repeat domain. Both the gene location and recessive genetic mode distinguish gm13 from other RGM resistance locus. Our findings provide a valuable genetic resource for breeding programs and advance the molecular understanding of rice immunity against gall midge.