John Buckley, Moseley, David O
Blair Buckley and David O. Moseley
Relatively new, compared to many of Louisiana’s crops, the soybean was initially adopted in the United States more than 100 years ago as a forage crop. At the time, to find suitable varieties for forage production, university soybean breeders selected varieties out of introductions from Asian countries. Time marches on, and through the decades the LSU AgCenter has helped Louisiana soybean producers adapt to major transformations to production through breeding and variety testing here at home.
The Louisiana Agricultural Experiment Station soybean breeding program began in the late 1920s with an emphasis on selection for forage production. Plant material selected for forage typically has prostrate growth habits, high biomass and low seed production. Avoyelles, released in 1931, was the first forage-type soybean released.
In 1940, there were only approximately 100,000 acres planted in Louisiana; however, as a shift to grain production occurred, the number of acres increased, marking the first major change in Louisiana soybean production. Uses of soybean plants began to change as the seed became a viable source for oil, and in the early 1940s, most soybean acres began to be planted for grain instead of forage.
In Louisiana, there were more than 200,000 acres of soybean planted by 1956, increasing to more than 1 million by 1967. Selection criteria included upright growth habit, decreased lodging (falling over from wind and rain), increased seed yield and decreased seed shattering. Bienville, released in 1958, was the first variety developed for seed production. The Bossier and Curtis varieties were released a few years later in the 1960s.
By the mid-60s, the first uniform soybean variety trial was established across the state to help producers select the highest yielding and most stable varieties. Uniform variety trials compare the same varieties across different locations and environments in replicated small research plots. The small plots help reduce the environmental variation between plots, and the multiple replications allow researchers to use statistics to determine differences between varieties.
From 1968 to 1979, an average of 16-20 varieties were screened at research stations across the state, which provided data in various environments. Initially, the varieties were predominantly from university soybean breeding programs.
A third transformation to Louisiana soybean production took place between the 1980s and early 2000s. Private companies began to enter more varieties by 1980, increasing the average number of varieties to approximately 40 by 1983. In the early 1980s, research stations began screening varieties for differences in yield potential and plant growth and development traits in different production practices. Plant growth and development traits include maturity, plant height, lodging, seed shattering and disease resistance. Variety yield potential and plant growth and development can change in different environments within a location, including irrigated and nonirrigated plots and soil types. From 1968 to 1983, maturity groups 5-8 were tested. Maturity groups describe the timing of growth and development of the plant variety. They range from 000, which is the earliest and best adapted to Canada, to 10. Generally, the higher the maturity group number, the later the maturity and the farther south it is adapted.
In the 1990s, with the introduction of herbicide resistance technology, soybean varieties were made available to producers from private companies as well as university soybean breeding programs.
Previously, producers in Louisiana would plant maturity groups 5-8 from mid-May to late-June. However, planting soybean varieties with an earlier maturity group at an earlier planting date was observed to promote higher yield potential and stress avoidance. By 2000, producers began to plant maturity groups 3-5 soybeans in mid-April to mid -to-late May.
Plant diseases, insects and environmental stresses emerge and change over time, greatly reducing soybean yield and profitability. The breeding program has adapted to address these issues, with the most economical method being for producers to grow resistant soybean varieties. The LSU AgCenter soybean breeding program has focused on identifying resistance to biotic stresses, such as insects and pathogens, and abiotic stresses, including weather conditions and soil salt content, that negatively influence plant growth and development and has incorporated that resistance into high-yielding soybeans:
In the 1960s, screening and breeding soybean for resistance against nematodes, southern green stink bug and the three-cornered alfalfa hopper began.
Because of outbreaks of stem canker, aerial blight, red crown rot and frogeye leaf spot in the 1980s, researchers began soybean resistance screenings. The Gregg variety, released in 1983, provided resistance to both the soybean cyst nematode and the reniform nematode.
The Buckshot 723 variety, released in 1990, was resistant to stem canker. Increasingly, the soybean breeding program began selecting for hard seed coats in the 1990s to combat seed weathering. During this time, varieties also began to be screened for salt tolerance at the Macon Ridge Research Station in Winnsboro.
Yield loss due to Cercospora leaf blight became a major concern to Louisiana soybean producers in the 2000s, and there is no resistant variety available yet. However, there are some fungicides that are moderately effective for control of the disease. The breeding program has screened soybean germplasm, breeding lines and varieties to identify Cercospora leaf blight resistance. Resistance is being incorporated into soybeans with high yield potential. Other soybean problems the breeding program is trying to combat include flood and drought damage.
As soybean production shifted to include varieties with earlier maturity and herbicide-resistant technology, the LSU variety testing program was transformed. By the early 2000s, there were approximately 150 to 200 varieties screened annually, mostly entered by private seed companies. The maturity groups consisted of 3-6, with most of the varieties split between maturity groups 4 and 5.
In 2020, there were 154 varieties entered in the official variety trial (OVT), testing resistance to herbicides including glyphosate, dicamba, glufosinate, 2,4-D choline and sulfonylurea. There are still conventional varieties that do not have resistance to nonselective herbicides.
Consistent through the years of variety testing in Louisiana, the main objective was to screen for performance in yield and abiotic and biotic stress resistance. Scientists began to screen the varieties for stresses as they would become problematic. Currently, varieties are screened for target spot, soybean rust, aerial blight and Cercospora leaf blight. They are also tested for salt tolerance, taproot decline and weathering resistance. Other types of field and lab testing screen varieties for resistance to nematodes, aerial blight, Cercospora leaf blight and stink bugs.
As production practices changed, LSU AgCenter soybean breeding and variety testing has guided producers in variety selection with unbiased research across the state. As production practices evolve, LSU AgCenter scientists will continue to breed and test new varieties to discover the highest yielding and most stable.
Blair Buckley is an associate professor at the Red River Research Station in Bossier City. David O. Moseley is an assistant professor and extension soybean specialist at the Dean Lee Research and Extension Center.
(This article appears in the spring 2021 issue of Louisiana Agriculture.)
Soybean plant developing pods. Photo by David O. Moseley
David O. Moseley is the LSU AgCenter state soybean specialist and in charge of the variety testing program for soybeans. Photo by Craig Gautreaux
Soybeans are being harvested and the seeds weighed in one of the demonstration fields in Beauregard Parish. Photo by David O. Moseley
Demonstration research plots were planted in farmers’ fields in 11 parishes in 2020. The parishes were: Avoyelles, Beauregard, Catahoula, East Carroll, Madison, Natchitoches, Pointe Coupee, Richland, St. James, St. Landry and West Carroll.