2011 Annual Report
1a.Objectives (from AD-416)
To map genes for Fusarium head blight (FHB) resistance and low mycotoxin contamination, and for pests such as Russian wheat aphid; Develop improved green plant regeneration techniques from barley tissue cultures for genotype-independent genetic engineering of disease and pest resistance; Develop transgenic barley lines
expressing combinations of pathogen response and anti-DON genes, test gene expression, and evaluate for effects on Fusarium graminearum and other fungal pathogens.
1b.Approach (from AD-416)
Single quantitative trait locus (QTL) lines for loci involved in FHB and mycotoxin resistance from Zhedar 2 will be developed by backcrossing, fine-mapped using all available molecular markers, and characterized in replicated field trials. Candidate genes from collaborative projects will be verified by inserting the genes into susceptible cultivars via transformation, and testing homozygous progeny in the field. RWA resistance genes in ARS germplasm releases will be mapped using a variety of molecular markers. The involvement of ethylene in tissue culture regeneration will be tested by manipulating ethylene levels with inhibitors and precursors. Optimal timing for ethylene exposure will be determined and tested using commercial barley cultivars. Genes responsible for ethylene perception, synthesis and regulation will be isolated and characterized by following their expression through the tissue culture process. Antifungal and antitoxin genes will be inserted into a commercial barley cultivar using particle bombardment. Resulting lines will be tested in the lab for gene expression using northern and western analyses, and in the field for reaction FHB and other diseases.
Barley lines carrying genes with potential antifungal effects were tested for Fusarium head blight (FHB) reaction and contamination by the mycotoxin deoxynivalenol (DON) in field trials. Two transgenic lines showed approximately 40% less DON than control plants in 4 years of field testing. These lines are being crossed to FHB resistant lines developed by barley breeders in ND and MN to see if the effects are additive. Ethylene is a plant hormone involved in response to disease and in regeneration from tissue cultures. The chromosomal location of 21 members of the gene families responsible for ethylene biosynthesis and reception were determined. Unique primers were designed for each member of the gene families for future gene expression studies.
New genes in barley for resistance to Russian wheat aphid. Barley is an important crop for production of feed, food, and beverages. The Russian wheat aphid is a major limitation for producing barley in the western US as aphid infestations cause major yield losses. Pesticide application to control the aphids is costly and has limited effects because the aphid causes leaf rolling, which protects the aphid from any spray exposure. So far, only three aphid resistance genes have been identified although 96 resistant barley lines have been identified. ARS researchers in Fargo, ND, Aberdeen, ID, and Stillwater, OK, used genetic mapping techniques to identify as many as 15 new genes in these resistant lines. DNA markers linked to these genes will be used to develop resistant cultivars with a variety of genes that are less likely to be defeated by the aphid. The availability of additional genes for aphid resistance provide better choices for barley breeders to incorporate resistance that will protect barley yield and quality as the Russian wheat aphid expands its habitat.
Naeem, R., Dahleen, L.S., Mirza, B. 2011. Genetic differentiation and geographical relationship of Asian barley landraces using SSRs. Genetics and Molecular Biology. 34:268-273.
Tyagi, N., Dahleen, L.S. 2011. Timing of Ethylene Modification Is Critical For Regeneration In Barley. Plant and Molecular Biology and Biotechnology. 4:47-55.
Thomas, W., Hayes, P., Dahleen, L.S. 2011. Barley: Production, Improvement, and Uses. Application of Molecular Genetics and Transformation to Barley Improvement. Book Chapter. 122-143.