水稻拟禾本科根结线虫抗性基因qRKN3的精细定位与候选基因分析

拟禾本科根结线虫对江西水稻生产造成重大威胁。Ch121是项目组自主选育的抗病水稻品种。申请人利用抗病Ch121和感病Kos构建的CSSLs群体在3号染色体定位到1个抗拟禾本科根结线虫主效QTLqRKN3，贡献率23%。进而构建了携有qRKN3区段的染色体单片段代换系，Kos-qRKN3 Ch121，渗入区段位于3号染色体RM6417-RM6783之间约1209Kb。Kos-qRKN3 Ch121与Kos间抗性差异显著，证明qRKN3真实存在。本研究拟在此基础上进一步构建高密度覆盖qRKN3的染色体片段代换系精细定位qRKN3；结合抗病近等基因系NIL-qRKN3CC和Kos的转录组测序结果，筛选定位区间内差异基因为抗病候选基因；通过干涉和过表达验证其功能；并利用关联分析法发掘其功能性突变位点和有利等位变异；为水稻抗拟禾本科根结线虫分子机理研究提供参考，为分子育种提高抗根结线虫病提供资源。

Root-knot nematodes (RKN), Meloidogyne graminicola has emerged as a major threat to rice in Jiangxi province. In our previous study, rice variety Ch121 showed relatively high level of resistance to RKN. Chromosome segment substitution lines (CSSLs) derived from a cross between the resistant variety Ch121 and a RKN susceptible variety Kos were generated for RKN resistance quantitative trait loci (QTLs) mapping. Genome-wide analysis of the linkage map constructed from the CSSLs showed that a major RKN resistance QTL, designated as qRKN3, was located on chromosomes 3 and its contribution rate to the total phenotypic variance reached 23%. Furthermore, single segment substitution line with qRKN3 was developed. The target fragment was located within 1209Kb region between markers RM6417-RM6783 on chromosomes 3. Phenotypic characterization showed significant difference between susceptible parent Kos and Kos-qRKN3 Ch121, which confirmed that qRKN3 was the true QTL for Ch121 resistance to RKN. To obtain fine location of this QTL, we conducted fine mapping in the secondary generation Based on these findings, more CSSLs will be constructed with the aim of fine-mapping of qRKN3. The whole genome expression profiles of resistant near-isogenic line and Kos after M. graminicola inoculation will be analyzed using RNA-seq technique. Taking the results of QTL mapping and RNA-seq together, the candidate genes will be screened to determine their resistance to RKN. Subsequently, the strongest candidates that involved in resistance to RKNs will be overexpressed in rice to validate their biological function. In addition, the sequence of the candidate gene in rice germplasm resources will be analyzed to see their functional mutational-sites. And the genes with potential beneficial value will be explored using the association analysis. This study will preliminarily ascertain the genetic and molecular mechanism of qRKN3 resistance to rice RKN, and provide theoretical basis for molecular design breeding.