In the Southeastern U.S., cucurbit production is vulnerable to the sweetpotato whitefly Bemisia tabaci and the viruses it transmits. There are limited control methods for the whitefly pest, including mulches, row covers, and spray programs. Unfortunately, none of these practices reduce the whitefly populations to zero, leaving whiteflies behind to transmit viruses. Therefore, host resistance is the best management practice, and the identification of resistant genotypes to whitefly transmitted viruses is a top priority. To aid watermelon breeding for resistance, 21 Citrullus genotypes were evaluated over two field seasons in Tifton, GA in 2022 and 2023. The traits evaluated were viral disease severity (AUDPC), Cucurbit leaf crumple virus (CuLCrV), Cucurbit yellow stunting disorder virus (CYSDV), and Cucurbit chlorotic yellows virus (CCYV) viral loads and in 2022 only, whitefly counts were collected to evaluate whitefly preference. Leaf tissue was collected 5 weeks after transplanting (WAT) in 2022 and 7 WAT in 2023. Total nucleic acids were extracted, and qPCR was performed to determine viral loads. Grif 16444 was the only genotype that had lower adult whitefly counts, indicating non-preference of this genotype. Over the two years there were three consistent genotypes with the statistically lowest AUDPC, two C. mucosospermus (PI 595203 and PI 494528) and one C. ecirrhosus (Grif 16444). In 2022, these three genotypes had significantly lower CuLCrV viral loads than the cultivar checks, however, in 2023 due to low CuLCrV presence there were no significant differences. For CYSDV and CCYV, there were no genotypes with significantly lower viral loads than the cultivar checks in both years. These wild crop relatives provide sources of resistance that can be used by breeders to improve cultivated watermelon.
