Two Mississippi State University breeders are developing breeding lines of cotton that show great hope against reniform nematode, a pest that caused $130 million in annual losses to the crop in the U.S. last year.
Peggy Thaxton at MSU’s Delta Research and Extension Center in Stoneville, Miss., and Ted Wallace on the university’s main campus have been testing cotton in both locations for a gene that provides resistance to reniform nematodes. After four years of laboratory and field research, their collaborative efforts for Mississippi Agriculture Forestry and Experiment Station have begun to pay off.
“We are the first public university to use marker-assisted selection on a large scale in cotton breeding to help identify plants with the gene that produces resistance to reniform nematodes,” Thaxton said. Marker-assisted selection allows researchers to look at organisms at the molecular or genetic level.
Nematodes are microscopic worm-like organisms that feed on plant roots. These pests can seriously damage crops and are difficult to overcome since they live under-ground. All current varieties of cotton are susceptible. Signs of nematode damage include plant stunting, yellowed leaves, reduction in fruit, slower growth, wilting and plant stress. Cotton nematodes have been identified in every state where cotton is grown.
“We were able to use a reniform nematode resistance gene that had been transferred from a wild species of cotton,” Thaxton said.
Thaxton and Wallace are working with ARS-USDA geneticists, Brian and Jodi Scheffler, who identify plants with correct resistant genes.
“Using marker-assisted selection to develop a new variety of cotton was much smoother because of MSU’s close connection with ARS-USDA, which has a facility next to DREC. Brian and Jodi helped us track and monitor the gene needed to develop this resistance,” Thaxton said.
Thaxton and Wallace transferred the resistance gene into plants of MAFES developed cotton breeding lines and grew offspring plants in breeding nurseries. After the cotton had germinated, the ARS-USDA examined tissue from young plant leaves for the resistant gene. Then Wallace and Thaxton had to harvest only the plants with the resistance gene.
“We pulled over five thousand leaf samples, and were delighted to learn that we had numerous plants with the resistance gene for reniform nematodes,” Thaxton said.
Thaxton and Wallace then planted 900 resistant plants at DREC and MSU. They now have 200 plots 40 feet long that have tested positively for the reniform-resistance gene.
“Now that Bayer CropScience is phasing out the common nematicide, Temik, producers have few options for controlling reniform nematodes in cotton. A reniform-resistant variety will be a windfall for cotton producers, especially those in the Southeast who have relied on nematicides to control nematodes,” Wallace said.
Nematode problems do not appear in just one season, and when present, can be challenging to manage. In the past, producers have had few methods for controlling nematodes. In addition to treating with Temik, another suggested approach was rotating crops with rice, corn, grain sorghum or soybean. Yet, when producers returned to planting cotton after crop rotation, reniform nematodes soon reappeared.
“We are pleased with the development of cotton breeding lines that show resistance to reniform nematodes. However, these lines will need several more years of testing before producers can benefit from this breeding effort,” Wallace said.
Development of breeding lines can take a minimum of 10 years.
This project was funded by MAFES, MSU, ARS-USDA and Cotton Incorporated.