032 Resistance to Papaya Ringspot Virus in Watermelon

Abstract

Watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] is a major crop in the southern U.S., where the most important virus diseases are papaya ringspot virus (PRSV), watermelon mosaic virus-2, and zucchini yellow mosaic. The most economical control of virus diseases of watermelon is probably through genetic resistance. Watermelon has not been screened extensively for resistance to PRSV. The objective of this research was to develop a suitable method for screening watermelons for resistance to PRSV and then to screen the USDA germplasm collection. To date, we have developed an effective method and have nearly completed the screening. Several of the 1283 accessions have shown resistance to the virus. Methods tests involved 10 isolates of PRSV, several watermelon accessions and multiple inoculation procedures. Seedlings were screened in greenhouse flats with six replications per test. Tests were rated visually on a 0 to 9 scale (0 = no damage, 9 = plant dead), as well as with ELISA to detect the presence of virus. The watermelon germplasm collection was screened in four separate runs of 1283 accessions with `Charleston Gray' as the susceptible check. This research will be useful for those interested in effective screening methods, and sources of resistance for development of improved watermelon cultivars.