Research HighlightsBreeding Soybeans for Resistance to Mature Soybean Seed Damage
By Teresa Wilkerson, Mississippi State University
Reductions in soybean grain quality can occur as a result of delayed harvest and/or late-season diseases, with more than 7% damage in some years. Phomopsis sp. infection in grain causes losses in all regions, and increases with overhead irrigation or rainfed environments. In 2017, as reported by the Southern Soybean Disease Workers, an estimated 52,500 metric tons (over 1.9 million bushels of soybean) of grain production were lost across 16 southern states. Symptoms include seed that is shriveled, elongated, moldy, chalky, discolored, weathered and with reduced germination and vigor. Harvested grain will incur reductions in monetary value (dockage) at the grain elevator if the combined seed damage (“damaged kernel total” [DKT])
is greater than 2%. Infection of developing soybean grain may be more severe in early-maturing cultivars, when the harvest is delayed and environmental conditions continue to be warm and humid during advanced growth stages. Current management strategies include crop rotation with non-hosts, tillage, fungicide applications during pod-fill, and resistant cultivars. However, information regarding cultivar resistance in commercial offerings is limited. This $249,896 project aims to improve soybean resistance to reduced seed quality by identifying novel sources of genetic resistance for biotic and abiotic stresses, and developing new and improved breeding lines.
Breeding lines were tested in environments prone to severe seed damage, and lines with significantly lower seed damage were identified. A combination of laboratory and field research is being implemented. The availability of genetic resistance to quality reduction in harvested grain is being increased by providing commercial and public breeders with access to the best (lowest DKT scores) lines for use in making crosses. In addition, by 2020, line(s) with significantly lower DKT and improved seed yield will be released for general use.
Field trials were conducted under shelters equipped with overhead irrigation, to ensure environmental conditions are conducive to reducing harvested grain quality. Plots include germplasm selected by breeders from yield trials exhibiting the least amount of seed damage.
Fungicides were applied during late reproductive stages, under shelters subjected to extreme conditions, to determine efficacy in prevention of losses associated with a reduction in quality.
Ultimately, one or more varieties, tested and grown in three different states, possessing differing qualities of seed, will be identified. Seed will be treated with different active ingredients to determine which products are effective and monitored for resistance to these active ingredients. In addition, treated and untreated seed will be observed at different planting populations to assess the benefit of treatment, increase planting population or both to compensate for poor seed quality.
Finally, outreach materials were developed to improve stakeholder awareness, preventing losses associated with a reduction in harvested grain quality.
This research addresses the need for better soybean tolerance to mature seed damage, which will have a direct impact on growers by helping them select the best genetics for resistance to mature seed damage and understand what management practices are effective for limiting reduced quality of harvested grain.
This project was funded by the soybean checkoff. To find research related to this research highlight or to see other checkoff research projects, please visit the National Soybean Checkoff Research Database.