Department of Biology, Utah State University, Logan, UT, 84322, USA.
Theor Appl Genet. 2021 Sep;134(9):2749-2766. doi: 10.1007/s00122-021-03856-5. Epub 2021 Jun 12.
Polygenic genome-wide association mapping identified two regions of the cowpea genome associated with different components of resistance to its major post-harvest pest, the seed beetle Callosobruchus maculatus. Cowpea (Vigna unguiculata) is an important grain and fodder crop in arid and semi-arid regions of Africa, Asia, and South America, where the cowpea seed beetle, Callosobruchus maculatus, is a serious post-harvest pest. Development of cultivars resistant to C. maculatus population growth in storage could increase grain yield and quality and reduce reliance on insecticides. Here, we use a MAGIC (multi-parent, advanced-generation intercross) population of cowpea consisting of 305 recombinant inbred lines (RILs) to identify genetic variants associated with resistance to seed beetles. Because inferences regarding the genetic basis of resistance may depend on the source of the pest or the assay protocol, we used two divergent geographic populations of C. maculatus and two complementary assays to measure several aspects of resistance. Using polygenic genome-wide association mapping models, we found that the cowpea RILs harbor substantial additive-genetic variation for most resistance measures. Variation in several components of resistance, including larval development time and survival, was largely explained by one or several linked loci on chromosome 5. A second region on chromosome 8 explained increased seed resistance via the induction of early-exiting larvae. Neither of these regions contained genes previously associated with resistance to insects that infest grain legumes. We found some evidence of gene-gene interactions affecting resistance, but epistasis did not contribute substantially to resistance variation in this mapping population. The combination of mostly high heritabilities and a relatively consistent and simple genetic architecture increases the feasibility of breeding for enhanced resistance to C. maculatus.
多基因全基因组关联作图鉴定出与豇豆对其主要采后害虫豆象不同抗性成分相关的两个基因组区域。豇豆（Vigna unguiculata）是非洲、亚洲和南美洲干旱和半干旱地区的一种重要粮食和饲料作物，在这些地区，豇豆象 Callosobruchus maculatus 是一种严重的采后害虫。培育对 C. maculatus 种群在储存中生长具有抗性的品种可以提高粮食产量和质量，并减少对杀虫剂的依赖。在这里，我们使用由 305 个重组自交系（RIL）组成的豇豆 MAGIC（多亲本、高级世代互交）群体，鉴定与抗豆象有关的遗传变异。由于对抗性遗传基础的推断可能取决于害虫的来源或测定方案，我们使用了两个不同地理种群的 C. maculatus 和两种互补的测定方法来衡量几种抗性。使用多基因全基因组关联作图模型，我们发现豇豆 RIL 对大多数抗性测量具有大量的加性遗传变异。包括幼虫发育时间和存活率在内的几种抗性成分的变异主要由染色体 5 上的一个或几个连锁基因座解释。染色体 8 上的第二个区域通过诱导早期退出的幼虫来提高种子抗性。这两个区域都不包含先前与侵害豆科作物的昆虫有关的基因。我们发现一些证据表明基因-基因相互作用影响抗性，但上位性并没有为这个作图群体的抗性变异做出很大贡献。大多数高遗传力和相对一致和简单的遗传结构的结合增加了对 C. maculatus 增强抗性的育种可行性。
