Location: Crop Genetics Research2011 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
Efforts to incorporate useful levels of resistance to reniform nematode into upland cotton continue. Replicated trials were initiated to evaluate the performance of advanced generation materials with moderate levels of reniform nematode resistance derived from less-adapted day-neutral Texas race stock lines. In addition to measuring effects on soil populations of reniform nematode, these materials will be assessed for yield and fiber quality. The best lines will be evaluated in replicated trials again in 2012 in anticipation of a germplasm release. We also are working to develop germplasm with resistance from five unique relatives of upland cotton, and marker assisted selection is being used as appropriate to facilitate this effort. Progeny from various crosses are evaluated, and distant relatives of cotton are being screened to identify novel sources of resistance for future work. Additionally, experiments to describe the number of genes involved and their inheritance in select Gossypium (G.) arboreum accessions are nearing completion. Evaluation of cotton production practices that could impact the reniform nematode population continues. Results from a completed study that compared conventional tillage to a no-till system did not reveal any significant effect of tillage on reniform nematode populations. Planting dates, irrigation, weed management, and chemical control options are being evaluated in field experiments, which take several years to complete. Results to date continue to indicate that the reniform nematode population is not affected by planting cotton earlier than normal or by various herbicide regimes. Field trials are in progress to determine the effectiveness of the recently registered nematicide seed treatments Aeris , Avicta, and VOTiVO, as compared to Temik. Temik has been used for many years but is being removed from the market, with all use in the U.S. to be discontinued by 2018. A series of three field trials at different locations were conducted evaluating the efficacy of seed treatment nematicides to manage the reniform nematode. These products were evaluated in combination with seed treatment insecticides and fungicides. Nematode numbers, which were high at harvest, were not correlated with nematicide treatment. Seed cotton yields sometimes benefitted from the use of VOTiVO, but these effects were not consistent across environments. In a separate test, the response of 18 commercial cotton varieties to treatment with VOTiVO was evaluated. VOTiVO did not affect reniform nematode counts, and use of this biological nematicide only improved seed cotton yield for two of the varieties tested.
1. Genes combined to fight reniform nematode infection in cotton. Unique sources of resistance to reniform nematode identified in two relatives of cotton (Gossypium aridum and Gossypium longicalyx) have been transferred to upland cotton (Gossypium (G.) hirsutum), but information on whether or not the genes could be combined into a single plant was lacking. ARS researchers at Stoneville, MS, developed a population from a cross between plants with these two sources of resistance and used molecular markers to determine that individuals within this population fell into four groups: marker for resistance from Gossypium aridum only, marker for resistance from Gossypium longicalyx only, markers for resistance genes from both sources, and no markers for resistance. However, when markers for resistance genes from both sources were present, the level of reniform nematode suppression improved only slightly compared to plants with only one marker. This work confirmed that the resistance gene from Gossypium aridum is different from and combinable with the gene from Gossypium longicalyx and expands our knowledge about these resistance genes and their utility in cotton improvement programs.
Stetina, S.R., Molin, W.T., Pettigrew, W.T. 2010. Effects of varying planting dates and tillage systems on reniform nematode and browntop millet populations in cotton. Plant Health Progress. doi:10.1094/php-2010-1227-01-RS.