Disease-Resistant Cowpeas Now Available

A cowpea strain identified by Agricultural Research Service scientists could give rise to new commercial cultivars with resistance to cowpea stunt disease.

Cowpea stunt is caused by two viral “cohorts”: cucumber mosaic virus (CMV) and blackeye cowpea mosaic virus (BICMV). In Georgia, South Carolina, Alabama and other states, about 1.5 million acres of cowpeas are grown for human consumption, silage or “green manure.” Worldwide, cowpeas rank among the top five food fiber crops since they can tolerate poor, dry soils. In some U.S. cultivars, severe cowpea stunt outbreaks can cause losses of up to 86 percent.

Breeding stunt-resistant cowpeas has proven difficult, and controlling the disease with pesticides isn’t economical. ARS plant pathologist Graves Gillaspie and assistant curator James Chalkley hope to remedy the situation with the cowpea germplasm line GC-86L-98.

Their enthusiasm stems from trial results since 1998 showing it resists CMV, and is immune to BICMV. By “resistant,” Gillaspie explains, the plant can still flower and bear seed despite some late-season CMV infection. In susceptible cultivars, like Coronet, symptoms can include stunted growth, yellow, curled leaves and poor seed yield. GC-86L-98 is immune to BICMV because no infection occurs, adds Gillaspie, with ARS’ Plant Genetic Resources Conservation Unit in Griffin, Ga.

Now, plant breeders can grow GC-86L-98 in plots as a germplasm resource for passing stunt-resistance genes into elite commercial cultivars. Its heritage can be traced to “PI 441918,” a cowpea collected from a Brazilian marketplace in 1978. Samples were later sent to the ARS Griffin lab and maintained there as part of a national cowpea germplasm collection.

GC-86L-98, which represents the ARS scientists’ top selection of stunt-resistant plants from the Brazilian cowpea, produces large, tasty white seeds, Gillaspie says. Seed requests can be e-mailed to him at [email protected], or submitted via the National Plant Germplasm System website at:

http://www.ars-grin.gov/npgs/orders.html

ARS is the U.S. Department of Agriculture’s primary scientific research agency.