Table_1_Mapping of quantitative trait locus reveals PsXI gene encoding xylanase inhibitor as the candidate gene for bruchid (Callosobruchus spp.) resistance in pea (Pisum sativum L.).xlsx

Pea (Pisum sativum L.) is an important legume crop for both food and feed. Bruchids (Callosobruchus spp.) are destructive insect pests of pea in the field and during storage. In this study, we identified a major quantitative trait locus (QTL) controlling seed resistance to C. chinensis (L.) and C. maculatus (Fab.) in field pea using F2 populations derived from a cross between PWY19 (resistant) and PHM22 (susceptible). QTL analysis in the two F2 populations grown in different environments consistently identified a single major QTL, qPsBr2.1, controlling the resistance to both bruchid species. qPsBr2.1 was mapped onto linkage group 2 between DNA markers 18339 and PSSR202109 and explained 50.91% to 70.94% of the variation in resistance, depending on the environment and bruchid species. Fine mapping narrowed down qPsBr2.1 to a genomic region of 1.07 Mb on chromosome 2 (chr2LG1). Seven annotated genes were found in this region, including Psat2g026280 (designated as PsXI), which encodes a xylanase inhibitor and was considered as a candidate gene for bruchid resistance. PCR amplification and sequence analysis of PsXI suggested the presence of an insertion of unknown length in an intron of PWY19, which causes variation in the open reading frame (ORF) of PsXI. Moreover, the subcellular localization of PsXI differed between PWY19 and PHM22. These results together suggested that PsXI encoding xylanase inhibitor is responsible for the bruchid resistance of the field pea PWY19.

豌豆（Pisum sativum L.）是兼具食用与饲用价值的重要豆科作物。豆象（Callosobruchus spp.）是大田豌豆在田间及仓储阶段的毁灭性害虫。本研究以抗虫品系PWY19与感虫品系PHM22杂交获得的F2群体为材料，定位到了控制豌豆种子对绿豆象[C. chinensis (L.)]及蚕豆象[C. maculatus (Fab.)]抗性的主效数量性状位点（quantitative trait locus, QTL）。在不同种植环境下的两个F2群体中开展的QTL分析，均稳定检测到单个主效QTL qPsBr2.1，该位点可同时调控豌豆对两种豆象的抗性。qPsBr2.1被定位在连锁群2的DNA标记18339与PSSR202109之间，依据种植环境与豆象种类的差异，该位点可解释50.91%至70.94%的抗性表型变异。精细定位将qPsBr2.1缩小至2号染色体（chr2LG1）上1.07 Mb的基因组区域，该区域内共注释得到7个功能基因，其中包括Psat2g026280（命名为PsXI），其编码木聚糖酶抑制剂（xylanase inhibitor），被认定为豆象抗性的候选基因（candidate gene）。对PsXI的聚合酶链式反应（polymerase chain reaction, PCR）扩增及序列分析结果显示，抗虫品系PWY19的PsXI基因内含子中存在一段未知长度的插入序列，该插入变异会导致PsXI的开放阅读框（open reading frame, ORF）发生改变。此外，PWY19与PHM22的PsXI蛋白亚细胞定位（subcellular localization）存在显著差异。上述研究结果共同表明，编码木聚糖酶抑制剂的PsXI基因是大田豌豆PWY19获得豆象抗性的关键遗传因子。