Evaluation of Plant Introduction Lines of Yellow Squash (Cucurbita pepo) for Resistance against Single Infection of Cucurbit Chlorotic Yellows Virus and Cucurbit Leaf Crumple Virus

Whitefly-transmitted viruses have emerged as a major threat to cucurbit production in the United States during the past several decades. Cucurbit chlorotic yellows virus (CCYV), Cucurbit yellow stunting disorder virus (CYSDV), and Cucurbit leaf crumple virus (CuLCrV) are the main arthropod-borne plant viruses in cucurbit crops, including yellow squash (Cucurbita pepo). Symptoms of these viruses include interveinal chlorosis, chlorotic spots, yellowing, and curling of the leaves. The evaluation of specific viruses affecting a plant is challenging because of the prevalence of mixed infections in naturally infected fields. To devise an efficient breeding-based management approach, two PI lines (PI 171625 and PI 171627) were screened in a greenhouse to assess their resistance to individual infections of CCYV and CuLCrV. These lines were compared against a susceptible cultivar Gentry in two separate trials. PI 171627 displayed delayed symptoms, a reduced virus load, and a smaller area under the disease progress curve (AUDPC) compared with PI 171625 and susceptible cultivar Gentry when the plants were infected with CCYV. However, the AUDPC for CuLCrV was the same for both genotypes and the commercial line. Accession PI 171627, which displayed delayed and milder symptoms, could potentially provide a source for resistance against CCYV for breeding program. Future research is needed to comprehend the underlaying mechanism to understand this response.