2010 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.
Efforts to incorporate useful levels of resistance to reniform nematode into upland cotton continued. Moderate levels of resistance from less-adapted day-neutral Texas race stock lines have been identified, and we had seed increase plots in place in 2009. Unfortunately, the seed quality from these plots was poor due to damage from fall rains, so additional seed increase work is taking place this season. We anticipate generating enough high quality seed to test these lines in replicated trials that have been delayed until 2011. Breeding work to develop cotton with reniform nematode resistance continues. In this project, we are attempting to transfer 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.
Evaluation of cotton production practices that could impact the reniform nematode population continues. Planting dates, tillage, irrigation, weed management, and chemical control options are being evaluated in field experiments, which take several years to complete. Results to date suggest that the reniform nematode population is not affected by planting cotton earlier than normal, by shifting from conventional tillage to a no-till system, or by various herbicide regimes. 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. However, very little Temik is being used by producers because of the cost of the nematicide and the labor and equipment required for application. The new biological nematicide Votivo was evaluated for the first time this year. Limited research had indicated that this nematicide may be more effective than other seed treatments in minimizing nematode damage to cotton, soybean, and corn roots.
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.
Genetic Diversity in Reniform Nematode Populations Described Using Microsatellites. Understanding variability in the pathogen population is important not only to improve our understanding of the basic biology of this organism, but because it may allow us to track how the pathogen responds to various management practices and it may allow us to detect the origin and spread of this pathogen in the United States. Using six populations of reniform nematode from four states, ARS researchers at Stoneville, MS, developed 156 molecular markers that will enable detection of the genetic variability within this species. Twenty-two of these markers were sensitive enough to detect differences among three populations collected from the same location in Mississippi. This information was distributed to the scientific community through presentations at national scientific society meetings, a scientific publication, and inclusion of the marker information in the publicly-available database Genebank.
Erpelding, J.E. 2009. Anthracnose disease response for photoperiod-insensitive Ethiopian germplasm from the U.S. sorghum collection. World Journal of Agricultural Sciences. 5(6):707-713.
Pettigrew, W.T., Molin, W.T., Stetina, S.R. 2009. Impact of Varying Planting Dates and Tillage Systems on Cotton Growth and Lint Yield Production. Agronomy Journal. 101:1131-1138.
Arias, R.S., Stetina, S.R., Tonos, J.L., Scheffler, J.A., Scheffler, B.E. 2009. Microsatellites Reveal Genetic Diversity in Rotylenchulus reniformis Populations. Journal of Nematology. 41(2): 146-156.