Location: Crop Genetics Research2008 Annual Report
1a. Objectives (from AD-416)
Evaluate tetraploid cotton germplasm for host plant resistance to reniform nematode. Begin introgression of genes for host plant resistance to reniform nematode into tetraploid upland cotton from candidate diploid A-genome germplasm. Evaluate the impact of biotic and abiotic crop production factors on reniform nematode populations in Mississippi. Assess the efficacy of cultural and chemical management options to minimize losses to reniform nematode in Mississippi.
1b. Approach (from AD-416)
Stabilize the phenotype of day-neutral Texas race stock lines with moderate levels of resistance to reniform nematode through self pollination, and characterize the heritability and action of genes involved in resistance in these tetraploid lines. Develop a phenotypic screening technique that evaluates root infection by reniform nematode and also allows the evaluated plant to survive to reproductive maturity. Determine if enough variability exists within reniform nematode populations to allow them to adapt to overcome host resistance. Improve efficiency and effectiveness of methods necessary to introgress genes from diploid A-genome Gossypium species into tetraploid G. hirsutum germplasm by choosing the most compatible lines and by developing methods to reduce endogenous contamination of in-vitro ovule cultures without inhibiting their development. Introgress reniform nematode resistance from G. arboreum accession A2-190 into G. hirsutum. Describe the influence of crop production practices such as irrigation, tillage, and planting date on reniform nematode population density. Evaluate the role of weeds as hosts for reniform nematode and determine their importance in maintaining inoculum levels of the nematode. Evaluate adapted cotton lines for tolerance to reniform nematode. Determine effectiveness of new commercial seed treatment nematicides for managing reniform nematode, compared to in-furrow nematicide applications. Determine if a combination of nematicide and rotation to corn will improve reniform nematode suppression over rotation used alone.
3. Progress Report
This research advances the goals of the National Program 303 Action Plan. Objectives 1 and 2 address Component 3, Plant Disease Resistance. Objectives 3 and 4 address Component 4, Biological and Cultural Strategies for Sustainable Disease Management. Research efforts to incorporate useful levels of resistance to reniform nematode into upland cotton are underway. Breeding efforts are continuing with the goal of transferring moderate levels of reniform nematode resistance from less-adapted day-neutral Texas race stock lines into commercially desirable lines. A multi-year experiment evaluating the impact of selected day-neutral Texas race stock lines on reniform nematode population levels in the soil has been established and is in its second year. In addition, the gene for reniform nematode resistance from LONREN-1 was transferred into Mid South adapted breeding lines. Progeny with the resistance gene are being identified using molecular marker BNL 3279. Work to transfer genes for resistance to reniform nematode into upland cotton from its distant relatives (objective 2) has been delayed by at least 12 months due to the August, 2007 resignation of the ARS geneticist assigned to the project. Despite the position vacancy, breeding efforts involving reniform nematode resistant progeny generated earlier by this project have continued. Efforts to identify cotton varieties that are tolerant to reniform nematode are continuing in field trials. Twelve cotton lines are being evaluated for the second year in a reniform nematode infested field by comparing nematode counts and seed cotton yields of each cotton line in untreated plots and plots treated with a nematicide. Lines reported to be tolerant to reniform nematode are being used as parents in crosses. Research to identify cultural and chemical methods that can minimize losses to reniform nematode is continuing. Crop production practices including tillage, irrigation, early planting, and nematicides are being evaluated in field trials. Several years will be required to complete these experiments. The ability of common Mississippi weeds to support growth and reproduction of reniform nematode is being assessed in greenhouse tests. Field trials are in progress to determine the effectiveness of newly registered and experimental nematicide seed treatment combinations such as Aeris and Avicta. Some research is being done in cooperation with scientists at other institutions. Research in objective 4 is being conducted by Mississippi State University scientists under a Specific Cooperative Agreement between ARS and the Mississippi Agricultural and Forestry Experiment Station (6402-22000-005-01S). Scientists at Pasteuria Bioscience and ARS researchers are working to identify bacteria that may work as a biological nematicide under a Specific Cooperative Agreement (6402-22000-005-04S) in support of objective 4. Scientists at Texas A&M University are cooperating on research listed in objective 2 under a Non Funded Cooperative Agreement between ARS and Texas A&M University (6402-22000-005-03N). Separate reports summarize work completed under these agreements.
5. Significant Activities that Support Special Target Populations