Virus-Resistant Melons Released

A plant pathologist with USDA's Agricultural Research Service in Griffin, GA, Gillaspie and ARS horticulturalist Robert L. Jarret screened 670 germplasm accessions in the Griffin watermelon collection to find the resistant lines. All told, 1,530 watermelon accessions are housed at Griffin and another 300 at the National Seed Storage Laboratory in Fort Collins, CO.

How resistant to the virus are the new lines compared to commercial varieties now on the market? Gillaspie says that in a 1992 field test with the most resistant line, only six percent of the plants became infected after being intentionally exposed to the virus. That compares to 95 percent infection of the commercial variety Baby Bush watermelon, he says.

Gillaspie says the resistant lines came from what are known as eguisi watermelons, which originated in Africa, in what is now Nigeria. "About 25 percent of our collection are eguisi and most of the virus resistance appears to be found in these melons," he says. The four lines that have been released came from eguisi melons from Nigeria and Zaire.

Gillaspie says he initially screened them in greenhouse and field studies against a Florida strain of the virus. Then, four of the most resistant lines were tested in the greenhouse against virus strains from Florida, Arizona, California, New York, Israel and Italy.

Gillaspie says he's received a lot of interest in the resistant melons from breeders in Florida, where the virus problem appears to be acute. Gillaspie stresses that limited quantities of seed for the new lines are available only to public and private breeders who must cross the lines with commercial types to develop new hybrids for public sale.

He says it could take five years or more for breeders to incorporate the resistant lines into the sweet-tasting melons that are popular summer picnic fare. -- By Sean Adams ARS.

A. Graves Gillaspie, Jr. is at the Plant Genetic Conservation Resources Unit, Griffin, Georgia, phone (770) 412-4777.