Southwest peanut producers are clamoring for a peanut that's resistant to Sclerotinia blight, a disease that can reduce yields as much as 60 percent and once established in a field is virtually impossible to eliminate.
Treatment costs range from $125 to $150 per acre.
“We estimate that 50 percent of the peanut acreage in Oklahoma is infested with Sclerotinia,” says Kelly Chenault, USDA-ARS Research Biologist at the Plant Science Laboratory in Stillwater.
Western Oklahoma, she says is clear of the disease but some 190,000 West Texas acres are vulnerable to infection.
“Seminole, Texas, has Sclerotinia; Hobbs, New Mexico, does not,” she says.
Hassan Melouk, research plant pathologist, says Georgia peanut farmers do not have Sclerotinia. Neither do growers in Florida or Alabama. Farmers in South Texas, south of San Antonio, have never seen it. North Carolina and Virginia are infected. “The more canopy an area has the more disease is likely,” he says. “Also, soils are different from one growing area to another.”
The disease moves with seed. “Once you get it you don't get rid of it, Melouk says. “One field had Sclerotinia established in 1981 and, even after seven or eight years of crop rotation with cotton, sorghum, and wheat it's still there.”
Breeding for resistance, given the potential damage, the long-term infestations and the high costs of controls, is critical.
Melouk and Chenault are making progress and hope to have Sclerotinia resistant lines available commercially within the next few years.
“We have one runner line and one Spanish line we plan to release in two or three years,” Chenault says. “Both are high oleic, have improved resistance to Sclerotinia blight, good yield potential and good seed quality. We still have to do sensory testing, UPPT for at least one year, and seed increase before we can release them.
“The runner line is designed to replace Tamrun OLO1, which was moderately resistant and high oleic, but also ended up having a hard roasted kernel problem. Buying points have made it clear to growers that they won't buy anything that is not high oleic from now on.”
Chenault and Melouk have three or four runner lines with excellent resistance to Sclerotinia blight, “much better than the ones to be released soon,” Chenault says. “These lines have been crossed with lines to introduce the high oleic trait into them. Southwest Runner has also been crossed with a high oleic line. Jupiter will be crossed with lines to boost Sclerotinia blight resistance and introduce the high oleic trait, producing a resistant, high oleic Virginia type peanut.”
Speed is important for peanut farmers who have been hammered by poor weather and depressed prices.
As they wait for new varieties Chenault and Melouk suggest growers plant GAO2C, which is (in field trials) moderately resistant to Sclerotinia blight and high oleic in nature with satisfactory yield and quality.
Melouk and Chenault are working with both traditional and transgenic breeding techniques and say the process from initial selections to variety release is much faster than it used to be. DNA markers, for instance, speeds the screening process. “With new testing procedures we can screen much faster than we used to,” Chenault says.
They face another obstacle: Currently, GMO peanuts are not acceptable in the edible market. “We hope to have something ready when it is accepted,” he says.