2012 Annual Report
Identification and characterization of two genes for Fusarium head blight resistance. Fusarium head blight (FHB) is a serious fungal disease that currently threatens wheat production in the U.S. Because the utilization of FHB-resistant cultivars is an effective approach for protecting wheat against FHB, new sources of FHB resistance have been in high demand by wheat breeders. ARS researchers in Fargo, ND, in cooperation with North Dakota State University scientists, identified a wheat line (PI 277012) with a high level of FHB resistance. Based on genetic analysis, they identified two major FHB resistance genes, one of which was not previously reported. The major FHB resistance genes and molecular markers are being used for developing durum and bread wheat cultivars with improved FHB resistance in several breeding programs.
The evolution of genes governing the domestication of modern bread wheat. The wheat gene 5AQ is known to play a major role in wheat domestication and has been studied extensively, but two additional forms, known as 5Bq and 5Dq, exist in wheat and have not been investigated. ARS researchers in Fargo, ND, determined that the 5Dq gene more closely resembles 5AQ than does 5Bq, but both 5Bq and 5Dq contribute to wheat domestication through an intricately regulated network involving all three genes. It was also determined that, once wheat was domesticated, the 5AQ gene was transformed to a hyperfunctionalized state and became a master regulatory switch, whereas the effects of the other two genes were reduced in comparison. This work provides useful knowledge regarding wheat domestication, development, and genetic regulation of complex traits that will help researchers devise strategies to increase wheat yields and productivity in the future.
Toxin expression and severity of wheat fungal disease. The fungal pathogen Stagonospora nodorum is a serious pathogen of wheat. Many strains of S. nodorum produce a toxin known as ToxA, but the strains differ in their ability to cause disease; the underlying mechanism(s) for strain differences is unknown. ARS researchers in Fargo, ND, determined that different ToxA-producing strains of the S. nodorum pathogen express the ToxA encoding gene at different levels. The levels of ToxA expression were highly correlated with disease severity of infected plants, suggesting that increased levels of toxin production leads to more disease. This research provides insights into how wheat pathogens may be manipulated to enhance the disease resistance of wheat.
Identification and marker analysis of Hessian fly-resistance genes in wheat. Synthetic hexaploid wheat (SHW) lines are excellent sources of resistance genes for diseases and insects in wheat, and they have been widely used in wheat breeding and genetic studies. Some of these lines may harbor resistance to Hessian fly, a serious insect pest for wheat in the U.S. ARS researchers in Fargo, ND, in cooperation with North Dakota State University scientists, evaluated 118 elite SHW lines for resistance to Hessian fly and identified 52 SHW lines with high or moderate levels of resistance. Based on marker analyses, it is predicted that 19 of the resistant lines carry novel Hessian fly-resistance genes. The resistant SHW lines identified in this study should be useful for development of resistant cultivars and for genetic and evolutionary studies of resistance genes.
Development of a DNA marker panel for oats. The development of useful DNA markers for oat has been lacking due in large part to the complex structure of the oat genome. An ARS scientist in Fargo, ND, in collaboration with oat scientists in the US, evaluated over 6,000 DNA markers and investigated the genetic diversity among a set of oat varieties from around the world. These results contributed to the production of a high-density DNA marker panel containing 6,000 DNA markers, which will provide oat researchers a useful genomic tool for oat improvement.
Introduction of stem rust Ug99 resistance genes into wheat. Stem rust race Ug99 has the potential to devastate world wheat production. Goatgrass is a wild relative of wheat that has genes conferring good levels of resistance to Ug99, but these resistance genes are difficult to introduce into cultivated wheat. ARS researchers in Fargo, ND and St. Paul, MN used chromosome engineering techniques to successfully transfer small segments of goatgrass chromosomes carrying the Ug99-resistance gene (Sr47) to durum wheat. Molecular markers that can be used to select the goatgrass chromosomal segment carrying the rust resistance gene were also identified. Durum wheat lines carrying Sr47 and the molecular markers developed in this research provide useful resources for developing wheat varieties with resistance to Ug99 and other stem rust races.
Faris, J.D., Zhang, Z., Rasmussen, J.B., Friesen, T.L. 2011. Variable expression of the Stagonospora nodorum effector SnToxA among isolates is correlated with levels of disease susceptibility in wheat. Molecular Plant-Microbe Interactions. 24:1419-1426.
Chu, C.G., Tan, C.T., Zhong, S., Xu, S.S., Yan, L. 2011. A novel retrotransposon inserted in the dominant Vm-B1 allele confers spring growth habit in tetraploid wheat (Triticum turgidum L.). Genes, Genomes, Genetics. 1:637:645.
Lu, S. 2012. Use of the yeast two-hybrid system to identify targets of fungal effectors. In: M. Bolton & B. Thomma (eds), Plant Fungal Pathogens: Methods and Protocols, Methods in Molecular Biology 835:165-189.
Yu, G.T., Wang, T., Anderson, K.M., Harris, M.O., Cai, X., Xu, S.S. 2012. Evaluation and haplotype analysis of elite synthetic hexaploid wheat lines for resistance to Hessian fly. Crop Science. 52:752-763.
Chu, C., Niu, Z., Zhong, S., Chao, S., Friesen, T.L., Halley, S., Elias, E.M., Dong, Y., Faris, J.D., Xu, S.S. 2011. Identification and molecular mapping of two QTLs with major effects for resistance to Fusarium head blight in wheat. Theoretical and Applied Genetics. 123(7):1107-1119.
Munoz-Amatriain, M., Moscou, M.J., Bhat, P.R., Svensson, J.T., Bartos, J., Suchankova, P., Simkova, H., Endo, T.R., Fenton, R.D., Lonardi, S., Castillo, A.M., Chao, S., Cistue, L., Cuesta-Marcos, A., Forrest, K., Hayden, M.J., Hayes, P.M., Horsley, R.D., Moody, D., Sato, K., Valles, M.P., Wulff, B.B., Muehlbauer, G.J., Dolezel, J., Close, T.J. 2011. An improved consensus linkage map of barley based on flow-sorted chromosomes and SNP markers. The Plant Genome. 4:238-239.
Zhang, Z., Belcram, H., Gornicki, P., Charles, M., Just, J., Huneau, C., Magdelenat, G., Couloux, A., Samain, S., Gill, B.S., Rasmussen, J.B., Barbe, V., Faris, J.D., Chalhoub, B. 2011. Duplication and partitioning in evolution and function of homoeologous Q loci governing domestication characters in polyploid wheat. Proceedings of the National Academy of Sciences. 108:18737-18742.
Klindworth, D.L., Niu, Z., Chao, S., Friesen, T.L., Jin, Y., Faris, J.D., Cai, X., Xu, S.S. 2012. Introgression and characterization of a goatgrass gene for a high level of resistance to Ug99 stem rust in tetraploid wheat. Genes|Genomes|Genetics. 2:665-673.
Simons, K., Anderson, J.A., Mergoum, M., Faris, J.D., Klindworth, D.L., Xu, S.S., Sneller, C., Ohm, J.-B., Hareland, G.A., Edwards, M.C., Chao, S. 2012. Genetic mapping analysis of bread-making quality traits in spring wheat. Crop Science. 52:2182-2197.