Wild peanut species may have DNA that can provide keys to improved stress tolerance, higher yield, and better quality for domestic varieties, says Charles Simpson, whose 48-year career as a Texas A&M AgriLife research plant breeder has been devoted to looking for specific genes in wild peanuts to make domestic varieties better.
In many of those years, he spent several months at a time in South America, where peanuts originated, searching for new, undescribed wild peanuts, and identifying genetic traits that allow them to thrive in climates as varied as the sub-Amazon rain forest or elevations as high as 2,000 meters (6,561 feet) above sea level, and in seasons of heavy rainfall or as dry as a West Texas drought.
Simpson, who has worked closely with peanut researchers all over the world, recently mourned the loss of close friend and colleague, Ing. Antonio Krapovickas, an Argentine botanist with whom he spent countless days bouncing over rutted roadways and many nights hunkered down by a campfire discussing peanuts, theories, and life in general.
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Although he officially retired several years ago, Simpson’s schedule tells a different story. He continues to work in his laboratory and greenhouses at the Texas A&M AgriLife Research and Extension Center in Stephenville, where he maintains a collection of wild peanut species. He crosses some of them with domestic varieties, looking for traits that will make peanuts more drought tolerant, disease resistant, and/or productive.
So far, 81 wild peanut species and only one cultivated species have been described. Simpson has co-authored descriptions for 20 of the wild species.
COLLECTION OF WILD SPECIES
Until 1996, he and team members collected wild species in various South American countries, left a sample with the country of origin, and brought samples to the U.S. to research and maintain at the Stephenville facility, and to place in the national collection at Griffin, Ga., and in the international collection in India. Failure by the U.S. failure to sign the Andean Pact revenue sharing agreement in 1997 resulted in a ban on taking plants out of those countries.
Wild peanuts grow in Brazil, Uruguay, Paraguay, Argentina, and Bolivia. “If a wild species is growing anywhere else in the world, it was moved there,” Simpson says. “Only three wild species will survive the winters at Stephenville, but with adequate moisture, wild peanuts will survive on their own in their native habitats.”
These wild species possess unique and important survival mechanisms, he says. Some produce underground tubers that hold water, and through periods of drought or during intense wildfires, the plants draw on this reservoir of moisture to survive. Some species develop long pegs that grow deep into the soil, or some distance away from the mother plant. The deep pegs are able to withstand surface stressors, and the pegs growing at a distance may survive if something happens to the mother plant.
Simpson shows seed from a wild peanut, with pods attached to a small string, called a peg. Another peg-like isthmus extends from the end of the pod, and another fruit (peanut) develops on the end of this one, creating a chain of peanut pods and seeds farther and farther away from the original plant. Pegs can be up to one meter (3.28 feet) long.
Light sensitivity in pegs also differs between cultivated and wild peanuts. “In wild species, light sensitivity is not so pronounced,” Simpson says. “Pegs of the Arachis wild species grow longer and deeper into the soil. Planted in a half-bushel basket, the pegs will grow all the way to the bottom.”
Conversely, pegs of cultivated peanuts push into the soil to a relatively shallow depth.
Seed dormancy also plays a role in wild species survival, says Simpson, who recalls planting a wild species in his home garden, then deciding to take it out to create room for other plants. The flower bed was without a wild peanut for eight years, and then a seed germinated and produced a plant.
“I’ve seen another seed from a hybrid remain dormant for 36 months,” he says, while another, if allowed to dry out, may not break dormancy. “We keep them moist,” he says.
The one cultivated species described in the literature probably resulted from native hunters and gatherers transferring wild plants into a garden where bees cross pollenated them, Simpson says. Cultivated peanuts have 40 chromosomes, he explains, while wild species have only 20.
He’s produced wild species hybrids that are sterile, but which spontaneously doubled the number of chromosomes and produced seed. “We can also use a chemical, colchicine, to double the number of chromosomes. It’s mostly trial and error, with a bit of art to it.” Timing and amount of chemical used also are factors.
Use of the chemical comes within the realm of conventional breeding, Simpson says. “We can double the number of chromosomes, and then cross with cultivated peanuts.”
Wild species have already contributed to improvements in cultivated varieties, he notes. “We made the first cross for leafspot resistance in 1972, and it also had nematode resistance.”
There was skepticism, Simpson recalls, about how long it would take, using wild species, to develop a cultivated peanut that had nematode resistance. “We did it in 13 years, producing three generations a year. It wasn’t a great variety, and it was short on yield. We made two more backcrosses and developed NemaTAM. But by the time we got seed increased, peanuts were moving to West Texas, where nematode problems were less important. The government peanut quota program also changed, and NemaTAM didn’t have a place. Also, the variety developed from the cross didn’t have resistance to tomato spotted wilt virus, so it wasn’t a good fit for the Southeast. “We didn’t patent the gene,” Simpson says.
The program was funded by the Texas Peanut Producers Board and Simpson credits Lindale Coan, who was TPPB president at the time, for having the foresight to support the breeding work (a peanut variety was later named for Coan).
Simpson has worked with peanuts for the past 48 years, but says he’s received a check from Texas A&M for 52 years. As a graduate student, he worked with forage grasses and with plant breeding and cytogenetics. The opportunity to work with peanuts “just looked like a real challenge,” he says. “What I knew about peanuts was that they came in a bag for 5 cents and tasted good, and I saw peanut fields on my way to and from College Station.”
GENESIS OF PEANUT CAREER
He credits B.C. Langley, the superintendent at the Stephenville Experiment Station, for encouraging him to work with peanuts. “He was my mentor for two years; I stayed in touch after he retired, and we often talked about peanuts.”
Simpson also worked with Walt Gregory in North Carolina, and it was Gregory who sparked his interest in wild peanut species. “In 1975, Walt asked me to go with him on a collection trip to South America. He said the project would last about three years.” In 1977, Simpson made the first of his 27 or 28 trips, during which, he estimates, he collected “probably 2,000 different accessions of wild peanuts.”
Gregory retired, but Simpson continued the collection trips and worked for many years with Antonio Krapovickas. “He turned over half the leadership to me,” Simpson says. Two wild species bear the names of Simpson’s mentors — Arachis krapovickasii and Arachis gregoryi. Krapovickas and Gregory returned the favor and named a species Arachis simpsonii.
The necessity to collect wild species was heightened with expansion of soybean acreage in Brazil, particularly, and other South American countries, Simpson says. “We wanted to collect in South America before wild peanuts were destroyed to plant soybeans.”
Opening up roads to provide access for soybean production also improved access to wild peanuts. “They cut roads into the sub-forest for 75 to 100 miles and cut side roads off those,” Simpson says. “That opened up the forest canopy and exposed wild peanuts, which took advantage of the open canopy and grew aggressively.”
They located numerous accessions before the roads were paved and wild peanuts were destroyed. “We probably missed a lot of populations, especially in Brazil,” he says.
LOOKING FOR TRAITS
The wild peanuts available in the Stephenville greenhouses may hold the key to improving peanut varieties, Simpson says. Modern plant breeding methods, including marker-assisted breeding techniques, will facilitate projects such as nematode resistance and yield enhancement.
He is working with Ph.D. candidate John Cason, and says multiple challenges face peanut breeders. “We have a problem, especially with the national collection, because funding has not kept up with inflation and other pressures. A lot of the transferred material has not survived. We still have some seed here, but we need to grow 500 accessions a year, and we can only grow about 100. Because of bees, we can’t grow them outside and maintain a pure collection.”
Only about 60 percent of the collection produces adequate seed, Simpson says. “We work hard to keep live plants going for the other 40 percent.” Researchers at the national collection have started planting some seed outdoors in Florida.
Maintaining the collection in the greenhouse is also difficult, he says. “We don’t use herbicides, because we don’t want to eliminate alleles. We have to spray for insects, and some plants won’t tolerate the spray, so we sometimes remove insects manually.” He doesn’t want the plants to become resistant to herbicides and other pesticides.
He’s working on projects to cross hybrids and cultivated peanuts to create hybrid vigor, and has looked into the possibility of the peanut producing seed without fertilization — something that hasn’t been reported in legumes. “If we can fix hybrid vigor, there is no telling what we can do with peanut yields,” he says.
Simpson is also concerned about the continuing reluctance to share varieties with other countries. “I haven’t brought back anything new for the collection since 1996,” he says. That’s frustrating to scientists who work across many borders to identify and collect wild species. “It has always been the Land Grant philosophy to help other countries produce their own food and make them independent.”
Simpson is well-respected among his peers in plant genetics and within the peanut industry. He was recently selected as the awardee and speaker for the Crop Science Society of America’s 2015 Calvin Sperling Memorial Biodiversity Lectureship, scheduled for Nov. 17 at Minneapolis, Minn. The lectureship brings in renowned biodiversity lecturers to share research experiences, knowledge, and views on biodiversity as they interface with crop agriculture and the interests of the Crop Science Society of America.
David Stelly, Texas A&M University soil and crop sciences professor and chair of the award’s international committee, says Simpson was selected because of his decades of significant contributions to peanut germplasm exploration, collection, introgression, and their use in crop improvement.
“These beautifully parallel the kind of contributions by Calvin Sperling before his untimely passing,” Stelly says. “The lectureship committee and Crop Science Society of America are honored to highlight Dr. Simpson and his contributions, which will be of enduring benefit to science and society.”
His contributions to Texas and Southwest peanut production have also been significant. “Dr. Simpson is a peanut research rock star,” says Texas Peanut Producers Board Executive Director Shelly Nutt. “He’s a larger-than-life figure. Traits he's discovered from South America, and maintained all these years in the wild species collection, have proven to be invaluable treasures as he pulls specific genes from wild species and introduces them into breeding lines. If not for his determination and dedication to improving peanut varieties, Texas peanut production wouldn't be where it is today.”
Kelly Chamberlin, peanut breeder at the USDA-ARS Center for Peanut Improvement in Stillwater, Okla., also acknowledges Simpson’s contribution to the industry. “Charles has been instrumental in gathering germplasm accessions from other countries for our U.S. germplasm collection. At times, he has literally put his life on the line for peanuts.
“He has been key in discovering nematode resistance in wild peanuts and in the introgression of that trait into cultivars still used in breeding programs today,” Chamberlain says. “I’ve worked with Charles in the past to develop Sclerotinia blight-resistant peanut varieties. He is truly a devoted peanut geneticist.”
“Dr. Simpson’s work on wild species has opened new avenues for peanut improvement that only a handful of researchers in the world are able to do,” says Mark Burow, professor, peanut breeding and genetics Texas A&M AgriLife Research and Texas Tech University Department of Plant and Soil Science
“Wild species contain genes for many traits, such as disease resistance and high oil content that the cultivated species lacks. But crossing the wild species to transfer genes into the cultivated materials is difficult. The crosses that Dr. Simpson made years ago have led to release of five nematode-resistant varieties (three in Texas and two in Georgia) all containing resistance from his original hybrids. We expect we also will see leafspot-resistant varieties soon using wild species as source material.”
Simpson, who turned 75 the day he set aside for the Farm Press interview, expects Cason to one day step in and take on the responsibility of maintaining the wild peanut species collection at Stephenville —and perhaps, at some time, to add to it. In the meantime, he and Cason work through the wild species, looking for desirable traits that will improve domestic peanuts. He’s convinced that improved yield potential exists in the wild species.
“Some of these species produce tremendous yields,” he says. “I strong believe we will increase yield.”
He has dedicated his career to making peanuts more productive, and less susceptible to disease, drought, and other stresses. He has made a difference, and he expects those who follow in his footsteps to find even more potential in wild plants growing in South America and in the greenhouses at Stephenville.