Evaluation of squash (Cucurbita pepo L.) genotypes for resistance to cucurbit chlorotic yellows virus

Authors: KAVALAPPARA, SARITHA - University Of Georgia; BAG, SUDEEP - University Of Georgia; LUCKEW, ALEXANDER - University Of Georgia; MCGREGOR, CECILIA - University Of Georgia; CULBREATH, ALBERT - University Of Georgia; Simmons, Alvin

Submitted to: Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2024
Publication Date: 3/10/2024
Citation: Kavalappara, S.R., Bag, S., Luckew, A., Mcgregor, C.E., Culbreath, A.K., Simmons, A.M. 2024. Evaluation of squash (Cucurbita pepo L.) genotypes for resistance to cucurbit chlorotic yellows virus. Horticulturae. 10(3):264. https://doi.org/10.3390/horticulturae10030264.
DOI: https://doi.org/10.3390/horticulturae10030264

Interpretive Summary: The Cucurbit chlorotic yellows virus (CCYV) is a plant pathogen that is transmitted by whitefly pests. This is a global agricultural problem because curcurbit crops, including summer squash in the United States, lack resistance to this virus. Research was done to validate resistance to CCYV by selected germplasm lines that had appeared to have some resistance to this virus based on our previous observations. All of the Plant Introduction (PI) accessions tested (including PI 512749, PI 615141, PI 136448, PI 442312, PI 458731, and PI 420328), had low amounts of the virus and displayed delayed and less symptoms as compared with the susceptible commercial cultivar Gentry. These results support that these accessions are potential sources of resistance to CCYV for use in breeding programs so that growers may have some relief from the problems of this virus in their cucurbit crops.

Technical Abstract: Cucurbit chlorotic yellows virus (CCYV), a Crinivirus transmitted by whiteflies, poses a significant threat to cucurbit crops globally. Summer squash (Cucurbita pepo L.), an important vegetable crop in the Southeastern United States, is particularly affected. The absence of commercially available resistant summer squash cultivars necessitates the exploration of resistant sources. Cucurbita germplasms with potential resistance to CCYV were previously identified through field screening. In this study, we describe the controlled greenhouse screening of these germplasm lines aimed at validating resistance to CCYV infection. The susceptible cultivar Gentry used as control exhibited early and severe symptoms in response to CCYV infection. In contrast, all the PI accessions tested, including PI 512749, PI 615141, PI 136448, PI 442312, PI 458731, and PI 420328, displayed delayed and less severe symptoms. Nevertheless, CCYV RNA accumulated in all the PI accessions. Lower symptom severity while harboring a considerable amount of CCYV indicates their inherent tolerance to the yellowing disease induced by CCYV. When comparing CCYV RNA accumulation in PI accessions with the commercial cultivar ‘Gentry’, lower virus titers were observed across all tested accessions. Specifically, PI 420328 and PI 458731 exhibited significantly reduced CCYV titers compared to the susceptible cultivar in both mass exposure and clip cage experiments. These accessions, displaying reduced symptoms and lower virus titers, hold promise as sources of resistance to CCYV in breeding programs. This study also highlights the importance of utilizing a reliable method to assay the resistance or tolerance of selected germplasm to infection by CCYV.