Location: Crop Genetics Research2009 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
Research to identify genetic and cultural methods to manage reniform nematode in cotton proceeded as anticipated. Most cultural studies are field experiments, which take several years to complete. A study evaluating 12 cotton lines for tolerance to reniform nematode was completed, but none of the entries evaluated demonstrated tolerance. Examination of a new set of materials for tolerance will not be initiated as originally planned due to the resignation of the scientist conducting the work. Efforts to incorporate useful levels of resistance to reniform nematode into upland cotton continue. Breeding efforts to transfer moderate levels of resistance from less-adapted day-neutral Texas race stock lines into commercially desirable lines resulted in several promising lines. Seeds of these lines are being increased to allow evaluation in replicated tests next year. Work to transfer genes for resistance to reniform nematode into upland cotton from its distant relatives resulted in development of resistant germplasm with associated molecular markers, as described in the Accomplishments section of this report. In addition, resistance from the related species Gossypium arboreum was transferred into upland cotton. Genetic studies and marker development for this source of resistance are underway. Progeny from additional crosses are being evaluated and distant relatives of cotton are being screened to identify novel sources of resistance for future work. Work to evaluate the impact of resistant cotton lines on nematode population development continues. A multi-year experiment evaluating the impact of selected day-neutral Texas race stock lines on reniform nematode population levels in the soil is in its third year. Due to variability in nematode densities in plots in the previous two years, a fourth year of the test will likely be required. A separate study evaluating the ability of selected nematode sub-populations to reproduce on the cotton lines is likely to be delayed for at least one year because sufficient progress has not been made in selecting reniform nematode sub-populations that reproduce on each of the moderately-resistant cotton lines in the study. Research to identify chemical methods that can minimize losses to reniform nematode continues. Field trials are in progress to determine the effectiveness of newly registered and experimental nematicide seed treatment combinations such as Aeris and Avicta as compared to Temik, which has been used for many years. Results collected to date suggest that Temik is more effective at controlling reniform nematode than the newer products, with higher rates being more effective but sometimes causing toxicity symptoms on plants. Some research is being done in cooperation with scientists at other institutions: Mississippi State University (Specific Cooperative Agreement, subordinate project 6402-22000-005-01S), Pasteuria Bioscience (Specific Cooperative Agreement, subordinate project 6402-22000-005-04S), and Texas A&M University (Nonfunded Cooperative Agreement, subordinate project 6402-22000-005-03N). Separate reports summarize work completed under these agreements.
1. Resistance to Reniform Nematode Successfully Transferred into Upland Cotton. Reniform nematode has become the predominant nematode causing yield loss on cotton in the Mid South Area of the United States. Currently, there are no commercially available cotton varieties with resistance to this pest. Scientists in the Crop Genetics and Production Research Unit in Stoneville, MS, have successfully transferred resistance to reniform nematode into cotton from a distant relative, Gossypium aridum. Genetic experiments showed that the resistance is controlled by a single dominant gene. Molecular markers closely associated with the resistance were identified, and they will allow cotton breeders to incorporate the resistance into productive cotton varieties more efficiently than traditional breeding. This research has the potential to fill a critical need for cotton varieties resistant to reniform nematode.
Stetina, S.R., Sciumbato, G.L., Young, L.D., Blessitt, J.A. 2009. Cotton Cultivars Evaluated for Tolerance to Reniform Nematode. Plant Health Progress. doi:10.1094/PHP-2009-0312-01-RS