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United States Department of Agriculture

Agricultural Research Service

Related Topics

Research Project: Reniform Nematode Resistance

Location: Insect Control and Cotton Disease Research Unit

2013 Annual Report


1a.Objectives (from AD-416):
The ultimate goal is to provide U.S. cotton growers with an economical solution to reniform nematodes, Rotylenchulus reniformis, which have been reducing yields over $100M per year. Through complex manipulations, we jointly created non-GMO lines extremely resistant to the nematode (e.g. LONREN-1 and LONREN-2) using a naturally occurring gene from a non-cultivated African species, Gossypium longicalyx. However, all such resistant lines are agronomically debilitated in many fields – the plants are smaller and less productive. Such effects were not unexpected, and are most likely due to alien genes linked to the nematode resistance. These probably cause susceptibility to domestic pathogens and/or commonly used herbicides. Objectives of the joint Texas A&M University and USDA, ARS research are:.
1)Break the linkages between the genes for reniform nematode resistance and the flanking genes that affect agronomic performance and fiber traits (Texas A&M University);.
2)Develop a rapid, accurate bioassay to measure seedling stunting associated with the chromosome segment introgressed from G. longicalyx, and use the bioassay to identify desirable recombinants (USDA); and.
3)Confirm resistance of recombinants to nematodes and stunting in the field (USDA).


1b.Approach (from AD-416):
To break the linkages between the genes for reniform nematode resistance and the flanking genes that affect agronomic performance and fiber traits, we will synthesize heterozygotes that contain nearby recombination events, create testcrosses, and screen progeny with linked molecular markers to find recombinants, then jointly test the desired recombinants experimentally to determine their resistance and agronomic phenotypes. Concommitant with this process will be the identification of markers progressively closer to the resistance gene. Develop a rapid, accurate bioassay to measure seedling stunting associated with the chromosome segment introgressed from G. longicalyx, and use the bioassay to identify desirable recombinants (USDA). Confirm resistance of recombinants to nematodes and stunting in the field (USDA).


3.Progress Report:

The goal of this project is to develop new cotton germplasm that is resistant or immune to the reniform nematode, a highly destructive pathogen of cotton in many areas of the U.S. Previous work under the project used molecular markers to hone in on the reniform-nematode-resistant gene. These markers facilitate finding plants that exhibit resistance to the reniform nematode, but plants must be tested to determine if they are stunted by seedling pathogens. In FY 2013, 15,000 first generation seed were generated to identify plants that show resistance to the reniform nematode and are not stunted by seedling pathogens. These 15,000 plants are currently being screened for stunt and reniform nematode resistance. As work by this project progresses, new information will be developed that will advance our understanding of the relationship between resistance to the reniform nematode and plant stunting. The work will provide foundational information to support efforts aimed at developing new reniform-nematode-resistant cotton cultivars that do not show stunting in the field and that will be appropriate for productive use by U.S. farmers.


Last Modified: 9/1/2014
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