Integrated transcriptome and BSA-seq analysis identifies a novel QTL for Meloidogyne graminicola resistance in rice HuaHang31.

Abstract

Key message: A novel QTL on chromosome 11 with 7 candidate genes regulating nematode resistance was identified by RNA-seq-based transcriptome and BSA-seq combination analyses, revealing the possible interactions between nematodes and plants. The resistant rice germplasms against Meloidogyne graminicola, which is a plant-parasitic nematode posing a significant threat to rice production, are very limited. Here, we identified HuaHang31 (HH31), an indica rice variety, as a novel source of high resistance against to M. graminicola through large-scale screening of 297 rice accessions using PF-127 assays. Histopathological and histochemical analyses revealed that HH31 significantly reduced nematode penetration, delayed juvenile development, and triggered reactive oxygen species accumulation and hypersensitive response in root tip cells post-infection. RNA-seq-based transcriptome profiling of HH31 and susceptible IR64 roots at 3-, 7-, and 12-days post-inoculation (dpi) highlighted the up-regulation of phenylpropanoid, flavonoid, lignin biosynthesis, and phytohormone signaling pathways (jasmonic acid, salicylic acid, ethylene) in HH31, suggesting their pivotal roles in nematode resistance. Additionally, bulk segregant analysis of two F₂ populations derived from HH31 crosses with susceptible varieties mapped a novel quantitative trait locus (QTL) on chromosome 11 (4.7-8.2 Mb). Within this region, seven nonsynonymous nucleotide-binding site-leucine-rich repeat genes exhibited root-specific expression and responsiveness to nematode infection, implicating their roles in resistance. Importantly, this QTL represents a distinct genomic region compared to previously reported resistance loci, highlighting its novelty. This study provides a new understanding of the genetic basis of nematode resistance and a valuable source for the development of nematode-resistant rice varieties, offering a sustainable strategy to mitigate yield losses caused by this pervasive pathogen.