Higher copy number of an Arachis hypogaea glutamate receptor-like candidate gene is associated with increased resistance to tomato spotted wilt virus

Abstract

Orthotospovirus tomatomaculae (tomato spotted wilt virus, TSWV) is one of the most destructive viruses of the peanut (Arachis hypogaea L.) crop, with significant economic consequences. Genetic resistance is desired to prevent major yield losses for growers. SSD6 and its progeny NC94022 have been introduced as resistance sources for breeding new varieties. Genetic evaluation of NC94022-derived populations previously reported multiple quantitative trait loci for resistance on chromosome Arahy.01. Subsequently, an insertion region from NC94022, and its parent SSD6, was found from whole genome sequencing. A unique quadrupled glutamate receptor-like (GLR) gene was identified within the insertion region as a potential candidate gene for resistance. Eight populations were derived from crosses made between a single recombinant inbred line (RIL) containing the insertion region and four copies of the GLR gene, and eight unique parents without those. Field evaluation over three generations revealed a significant increase in TSWV resistance when the insertion region was present with high GLR copy number. All populations showed improved resistance when compared with susceptible varieties and their unique parents, while only a few were as resistant as NC94022 or the RIL parent, perhaps due to GLR gene copy number variation that may be attributed to early generation heterozygosity. These results suggest that improved TSWV resistance from SSD6 or NC94022 may be most efficiently selected by screening for higher GLR gene copy number.