Progress 09/15/01 to 09/30/04
Outputs
Objective 1: to map and clone resistance genes to Russian wheat aphid (RWA) in wheat. 3 high density genetic mapping populations screened for their reaction to the RWA. Three markers were linked to the Dn4 gene. Markers Xgwm106 and Xgwm337 flank Dn4 at 5 cM and 9 cM. Additional RFLP markers were linked to Dn4 and Dn7. 50 genes were differentially expressed in wheat seedlings during aphid feeding but none were linked to Dn4 or Dn7. Five of 78 Pakistani hexaploid lines showed resistance to the RWA. 100 accessions of Triticum tauschii were screened without finding new resistance sources. Efforts continue to find markers tightly linked to Dn4 or Dn7 and clone the genes via a map-based approach. Objective 2: restructured to address a new RWA biotype. Dryland crop rotations were established at three sites in eastern Colorado. Comprehensive agronomic and pest data have been collected sine since 1998. Aphid pests, their natural enemies, and all major pests are monitored.
Growing conditions have ranged from very dry to severe drought. In 2003 a new RWA biotype appeared at the Lamar site. 59 species of ground beetles were collected from 2 and 3 year rotations at the Briggsdale, Akron and Lamar locations, 51 in 2002 and 49 in 2003. 8, 13 and 2 species were unique to Akron, Briggsdale and Lamar respectively. Year and location had more influence than crop rotation on carabid abundance and species diversity. Sunflower had more overall carabid abundance due to two Harpalus species. In 2004, 43 of 91 RWA samples from Colorado and the southern Nebraska Panhandle were characterized as Biotype 1. The remainder were Biotype 2 or some other Dn4 virulent biotype. All Biotype 2 samples were from eastern Colorado. A third biotype was collected in Montezuma County. Biotypes 1, 2 and Montezuma have been characterized with a set of 20 differentials. Biotype 2 had greater fecundity, nymphs produced per day, maximum nymphs per day and intrinsic rate of increase, averaged
over 2 cultivars and 3 temperatures. No additional biological differences have been noted to date. Additionally no differences in management have been noted other than cultivar response. Fieldwork on development of a GIS based, predictive model for RWA Overwintering Success was completed. 3 years of data collection yielded D. noxia densities over three sampling periods at 2547 georeferenced locations. D. noxia densities were used to develop initial GIS-based models. Soil maps were developed for each site. Landsat-7 Enhanced Thematic Mapper images were collected at each site biannually. Temperature loggers were used on an hourly basis with approximately 20 logger locations per site. Temperature layers are being developed using these data. Precipitation and temperature data were collected daily by CoAgMet weather stations located near each site. A 30-meter USGS Digital Elevation Model has been used to develop elevation, aspect, absolute aspect and slope layers for each site.
Impacts
Total direct losses to Colorado growers from RWA have been up to $27 million in a single year with average total direct losses above $11 million per year since 1987. This is an interdisciplinary research program aimed at providing growers with environmentally sound, cost effective solutions to the Russian wheat aphid problem.
Publications
- Anderson, G.A., Papa, D., Peng, J.H., Tahir, M. and Lapitan, N.L.V. 2003. Genetic mapping of Dn7, a rye gene conferring resistance to the Russian wheat aphid in wheat. Theor. Appl. Genet. 107:1297-1303.
- Haley, S. D., Peairs, F. B., Walker, C. B., Rudolph, J. B. and Randolph, T. L. 2004. Occurrence of a new Russian wheat aphid biotype in Colorado. Crop Sci. 44:1589-1592.
- Miller, H. R. 2004. Carabid beetle (Coleoptera: Carabidae) seasonal occurrence and species composition in Colorado dryland cropping systems. MS Thesis, Colorado State University.
- Peairs, F. B., Haley, S. D. and Johnson, J. J. 2004. Managing the new Russian wheat aphid biotype. Pp. 22 - 24 in Johnson, J. J., ed. 2004. Making better decisions: 2003 Colorado wheat variety performance trials. Colorado State Univ. Agric. Exp. Sta. Tech. Rep. TR04-03, 32 pp.
- Peterson, G. A., Westfall, D. G., Peairs, F. B., Sherrod, L., Poss, D., Gangloff, W., Larson, K., Thompson, D. L., Ahuja, L. R., Koch, M. D. and Walker, C. B. 2004. Sustainable dryland agroecosystem management. Colorado State Univ. Agric. Exp. Sta. Tech. Bull. TB04-05, 124 pp.
- Tahir, M., Lawrence, C., Lapitan, N.L.V. 2002. Characterization of differentially expressed cDNAs in response to Russian wheat aphid feeding in wheat. Plant and Animal Genome IX Abstracts, Plant and Animal Genome Meetings, San Diego, CA. p. 265.
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Progress 01/01/03 to 12/31/03
Outputs
Cropping system rotations were established at three sites in eastern Colorado in 1997. The three locations were near Nunn (N), Akron (A), and Lamar (L), Colorado. Unfortunately, the cooperating farmers at the Nunn site sold their land to developers. A new site, similar in soil and climatic variables was identified in the Briggsdale, CO area and establishment of plots was begun in the fall of 1998. Crop rotations now in place at each of the current sites are Briggsdale (B): Wheat/ Fallow, Wheat/ Proso Millet/ Fallow, Wheat/ Wheat/ Corn/ Corn/ Sunflower/ Fallow, Opportunity; Akron: Wheat/ Fallow, Wheat/ Corn/ Fallow, Wheat/ Corn/ Proso Millet/ Fallow, Wheat/ Corn/ Millet; Lamar: Wheat/ Fallow, Wheat/ Sorghum/ Fallow. All sites have plots that are large compared to most conventional experiments. Plot sizes for B, A, L are 27m x 125m, 29m x 58m, and 32m x 42m, respectively. During the wheat phase plots are divided in half lengthwise. A RWA susceptible wheat cultivar is
planted on one side and a RWA resistant wheat cultivar is planted on the other. At the L site, grazing subtreatments were established in the wheat. (Grazing cattle on wheat is a common practice in the Lamar area.) Data collected since 1998 include grain yield for all crops, soil nitrogen at wheat planting, residues at wheat planting, pest and beneficial insect populations in all crops and weather data at each site. Aphid pests and their natural enemies are the primary focus of the insect sampling effort, although major pests of all crops are monitored. Since project initiation, we have established long term monitoring of several pest species using suction and pheromone traps. Additionally, we have implemented sampling methods for locally important pests at important crop growth stages. Long term weed monitoring was initiated in the 2000 growing season. 2002 Conclusions: No conclusions could be drawn due to the effects of the severe drought. 2003 Observations: Growing conditions were
much more favorable in 2003, and adequate to good yields were expected for all crops at all three locations. On 28 Mar 2003 a new RWA biotype was collected from damaged Prairie Red wheat in SE Colorado. Greenhouse studies confirmed that this biotype is virulent to all wheat-derived sources of resistance in the CSU wheat breeding program. The magnitude and extent of this problem are currently unknown, but clearly it is a significant threat to the wheat industry in Colorado and neighboring states. This development has forced the partial redirection of the Colorado RWA project planned for 2003 and 2004.
Impacts
From 1987 to 2002, total direct losses to Colorado growers from RWA have been up to $27 million in a single year with average total direct losses above $11 million per year. In 2003, a new biotype of the RWA was discovered in Colorado making reliance on existing resistant cultivars highly problematic and thus reducing management options and increasing the likelihood of high economic loss. This is an interdisciplinary research program aimed at providing growers with environmentally sound, cost effective solutions to the Russian wheat aphid problem.
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
This project has two broad objectives: 1) Identifying new genes imparting resistance to the Russian wheat aphid (RWA) and incorporating them into commercially acceptable wheat varieties, and 2) Integrating all the available control tactics into the most effective, efficient, and environmentally sound production systems that can be devised for the Great Plains. Objective 1. The main thrust under this object is to map and clone genes conferring resistance to the Russian wheat aphid (RWA) in wheat. Progress in this project was made in several areas. Three genetic mapping populations to allow high density mapping of the resistance genes were developed and screened for their reaction to the RWA. Two microsatellite markers and a morphological trait marker (red glume) were linked to the Dn4 gene. The microsatellite markers Xgwm106 and Xgwm337 flank Dn4 and are at distances of approximately 5 cM and 9 cM, respectively, from the gene. These markers are PCR-based and proved to
be useful for marker-assisted-selection in the wheat breeding program of Dr. Scott Haley. Additional RFLP markers were linked to Dn4 and Dn7. Last year, we reported the identification of 50 genes that are differentially expressed in wheat seedlings during aphid feeding. These clones fell under five categories: 1) plastid genes, 2) defense response genes; 3) retrotransposons, 4) genes associated with human tumors and 5) a category of novel genes. A paper describing these results was submitted. These clones were mapped genetically, however, none of these were linked to Dn4 or Dn7. Screening of new germplasm for new sources of resistance was also conducted. Seventy-eight hexaploid lines were obtained from the Plant Genetics Resources Institute in Pakistan. This germplasm constitutes land races collected from higher altitude areas of region bordering Pakistan and Afghanistan. Of these, 5 showed resistance to the RWA. These are being studied further to determine whether resistance genes
contained in them are novel or allelic with previously identified genes. One hundred accessions of Triticum tauschii, the D-genome donor of wheat, are currently being tested for resistance. Further analysis of a bacterial artificial chromosome (BAC) clone suspected of containing the DN4 gene turned out not to contain the gene. Efforts are therefore ongoing to find markers tightly linked to Dn4 or Dn7 and clone the genes via a map-based approach. Objective 2. Over the past several years, experimental dryland cropping systems were established in eastern Colorado. Long-term studies were initiated to compare the experimental systems with typical wheat production systems in the area. The experimental systems were designed to test the optimization of environmentally sound pest management tactics. Progress in this research was minimal in this reporting period because of the severe drought. However, the experimental systems are well established and data will be taken in subsequent years.
Impacts
Total direct losses to Colorado growers from RWA have been up to $27 million in a single year with average total direct losses above $11 million per year since 1987. This is an interdisciplinary research program aimed at providing growers with environmentally sound, cost effective solutions to the Russian wheat aphid problem.
Publications
- Tahir, M., Lawrence, C., Lapitan, N.L.V. 2002. Characterization of differentially expressed cDNAs in response to Russian wheat aphid feeding in wheat. Plant and Animal Genome IX Abstracts, Plant and Animal Genome Meetings, San Diego, CA. p. 265.
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Progress 01/01/01 to 12/31/01
Outputs
This project has two objectives: 1) Identifying new genes imparting resistance to the Russian wheat aphid (RWA) and incorporating them into commercially acceptable wheat varieties, and 2) Integrating all the available control tactics into the most effective, efficient, and environmentally sound production systems that can be devised for the Great Plains. Objective 1. The primary emphasis of this portion of the project is to map and clone genes conferring resistance to RWA in wheat. CDNA libraries were made from a resistant wheat genotype (94M370) from both aphid-infested and non-infested leaf tissues. Subtractive hybridization was performed between the cDNA from infested and non-infested material to identify genes that were differentially expressed during aphid feeding. The DNA sequences of 50 positive clones were determined and analyzed. Approximately 50% of the clones were plastid genes. The other 50% represent clones that were previously associated with
defense-response mechanisms in plants, retrotransposons, and genes associated with human tumors. These results provide insights on the molecular mechanism of resistance to the RWA and may lead to the cloning of genes that are useful for genetically engineering resistant genotypes. Great strides were achieved toward efforts to clone a RWA resistance gene by map-based cloning. One BAC clone was identified to contain the two DNA markers flanking the Dn4 gene. If the genetic map is confirmed, this means we have already cloned the Dn4 gene. Recombinant inbred lines segregating for Dn7 and F2-derived F3 families segregating for Dn4 were produced for high-resolution mapping of Dn7 and Dn4. Finally, 140 lines of Triticum dicoccoides obtained from Israel were screened with RWA to identify new sources of resistance. The resistance gene Dn7 was genetically mapped using RFLP markers. In a collaboration with others, the DNA sequences of 1000 cDNA clones containing sequences expressed during RWA
infestation in a line containing Dn7, were determined. Eighty-five percent of the cDNAs were known in the existing databases and 15% represented undescribed, new wheat cDNAs. In a previous study, we determined the physical distance (no. of DNA base pairs) between the DNA markers flanking Dn4 using FISH. This information is important for map-based cloning of the gene. The two markers flanking Dn4 are less than 1 megabase apart and could be as close as 1 kilobase. This finding was a breakthrough. It opens up the possibility of cloning the Dn4 gene and other genes in wheat, despite its large genome size and low level of genetic polymorphism. It demonstrated that even though the genetic distance between markers may be large, the physical distance may be small and therefore wheat genes are amenable to map-based cloning. Objective 2. Experimental dryland cropping systems were established in eastern Colorado. Long-term studies were initiated to compare the experimental systems with typical
wheat production systems in the area. The experimental systems were designed to test the optimization of environmentally sound pest management tactics.
Impacts
Total direct losses to Colorado growers from RWA have been up to $27 million in a single year with average total direct losses above $11 million per year since 1987. This is an interdisciplinary research program aimed at providing growers with environmentally sound, cost effective solutions to the Russian wheat aphid problem.
Publications
- Miller, C.A., Altinkut, A., and Lapitan, N.L.V. 2001. A microsatellite marker for tagging Dn2, a gene conferring resistance to Russian wheat aphid in wheat. Crop Science 41:1584-1589.
- Lapitan, N.L.V., Stephens, J.L., Brown, S.E., Altinkut, A., and Knudson, D.L. 2001. Integration of the genetic and physical maps of barley and wheat based on FISH with cDNAs and BACs. Plant and Animal Genome IX Abstracts. p. 48.
- Peterson, G.A., Westfall, D.G., Peairs, F.B., Sherrod, L., Poss, D., Gangloff, W., Larson, K., Thompson, D., Ahuja, L.R., Koch, M.D., and Walker, C.B. 2001. Sustainable dryland agroecosystem management. Tech Bull, TB01-2 Agric. Exp. Stn., Colo. State Univ., Fort Collins, CO.
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