USDA’s southern pea cultivar development
In Charleston, S.C., USDA plant geneticist Richard Fery has spent his career striving to meet the demands of growers and processors by developing varieties of southern pea and pepper that fit the changes in how growers and processors operate.
Vigna unguiculata (aka southern pea or cowpea) is an important vegetable crop in the southeast U.S. The crop is not only an important processing crop, but is also a popular home garden and fresh market item. Ninety percent of the processed crop is the so-called pinkeye southern pea. However, there are many cultivar types, and in the last 40 years, Fery has worked on all of them. The focus of Fery’s cowpea research is yield and nematode resistance, but aesthetics have played a big part in his work, as well.
Stores and farmer’s markets feature popular varieties like “pinkeye,” “crowders” and “creams,” either in the pod or freshly shelled and ready to eat or cook. Historically, even the cowpeas destined for the processing plant were harvested and processed fresh.
In the last generation, growers have moved away from hand harvesting to utilizing mechanized pea-viners and, most recently, to using grain combines. The current harvesting methodology is cheaper, because it relies on less manpower. However, the grower mustwait to harvest the crop until it’s dried. After harvest, the majority of southern pea crops are sent to processing plants, where they are either canned or frozen.
Consumers expect frozen cowpeas to look like fresh cowpeas: green. As it dries, the fresh green pea with the pink eye turns cream colored. To help the freezing industry meet consumer expectations, Fery developed two popular cowpea varieties that maintain their green coats through the drying, blanching and freezing process. To do this, he first had to identify the phenotypes and the genes that help certain varieties of beans keep their color.
About 35 years ago, researchers at Auburn University discovered a gene called Green Testa (testa means seed coat). Twenty years ago, Fery and his colleagues at USDA found a gene that produces and maintains a green seed and a green seed coat. They called the gene Green Cotyledon, and Fery bred it into a classical pinkeye cowpea. The result was a variety called Charleston Greenpack, which Fery released in 1997. Charleston Greenpack was quickly accepted by the frozen food industry, and Fery reports that today it is probably the leading freezing variety.
Despite the success of Charleston Greenpack, Fery used germplasm from the variety to develop a new cultivar to replace it. “Color loss is a critical problem in production systems where preharvest chemical desiccants are used to facilitate mechanical harvesting operations. The seven-day delay between application of the desiccant and initiation of harvesting operations can result in serious color degradation,” he wrote in 2007.
In 2006, Fery released GreenPack-DG. (DG stands for double green.) Because this variety has both the Green Cotyledon gene and the Green Testa gene, the color is greener and more uniform than the dry seeds of its parent cultivars. In addition, the seeds are less susceptible to color loss due to delayed harvesting. This gives the farmer leeway to leave his crop in the field without degrading color. “Charleston Greenpack must be harvested immediately after pod drying to ensure a high-color product, but GreenPack-DG has a considerably larger harvest window,” Fery reported in HortScience, just after he released the variety.
In 2008, Fery began a new breeding program to develop pinkeye-type southern pea lines with yield potential equivalent to leading blackeye-type bean cultivars.
Utilizing GreenPack-DG and the high-yielding blackeye bean cultivar California Blackeye #46 as the parental lines, Fery has been working to break the yield barrier in pinkeye-type southern peas.
Despite the availability of high-tech equipment, Fery and his colleagues rely on traditional breeding methods. “I’ve asked industry if they want GMO,” says the geneticist. “Industry doesn’t want GMO. Industry is doing okay without GMOs, and they just don’t want to deal with the image, I guess.” Fery notes that despite the growing number of genetically modified crops in the U.S. (soy, corn, cotton, tomatoes, salmon, etc.), the technique is not as popular in specialty crops. In fact, USDA researchers in Charleston do not do any GMO work.
Crossing GreenPack-DG and CB-46 using a single-seed-descent (SSD) breeding procedure, Fery has been able to quickly advance progeny populations at the rate of three or more generations per year. Last spring, he had 50,000 seeds of the first segregating population of the cross (F2). He and his colleagues grew 20,000 to 30,000 F2 plants in the field. The SSD procedure enabled Fery to monitor the success of the cross and make necessary adjustments. Using SSD also afforded Fery the opportunity to select the plants with the highest yield before the lines ‘fixed’. The researchers selected 400 to 500 high yielding F2 plants. In winter 2009-2010, Fery grew two additional generations in the greenhouse. In summer 2010, Fery planted 30 lines from the F5 generation. The next step is to select the plants from the F5 generation and begin growing F6.
“This next month or so, we’re going back in the greenhouse with F6 lines, then in winter/spring, we’ll have F7 lines in the greenhouse and next spring/summer we should have an F8 generation in the field,” he reports. “F8 lines are quite homozygous, so I feel safe doing bulking.” Fery will grow a whole plot out and harvest all the plants together. In the subsequent three to four years, the researcher will conduct replicated field tests, to gain the confidence that what he has bred is better than what he’s trying to replace.
Ultimately, Fery will enter his lines in regional trials, to test them in 10 or 12 locations throughout the southeastern U.S. There are fewer testing locations today than in years past, however, due to budget constraints at land grant universities and other public breeding programs. Still, the project is right on schedule, and growers in the southeastern U.S. should benefit from the research by 2017.
Read about Fery’s research into nematode resistant peppers next month.
The author is a freelance writer based in Massachusetts and a monthly contributor to Growing.