2010 Annual Report
1a.Objectives (from AD-416)
Identify, characterize, and develop grass germplasm suitable for turf uses with improved heat tolerance, disease tolerance, drought tolerance, water-use efficiency, and salt tolerance using conventional and molecular methods to improve the germplasm enhancement process. Emphasis will be placed on heat tolerance and disease resistance through the period of this project plan. Identify molecular markers and construct linkage maps of bentgrass (Agrostis spp.) that identify regions that impact heat tolerance. Work will also be conducted through cooperative agreements on low maintenance turfgrass species such as Koeleriamacrantha and Danthoniaspicata. Identify genetic markers for bentgrass foliar disease resistance to (dollar spot) and use them to select highly resistant Agrostisgermplams. Construct comparative maps to align genomes of selected forage and turf plants with cereal food crops and utilize this information to improve grass genetic resources.
1b.Approach (from AD-416)
Collect germplasm from natural grasslands worldwide of species having potential as turfgrasses; collaborate with forage, rangeland, and turfgrass scientists to identify, locate and collect germplasm. Study establishment, persistence, survival under different management strategies, and resistance to pests and diseases. Determine presence of endophytes, and whether endophytes affect resistance to pests, diseases, or environmental stresses. Examine physiology under different stresses and inputs to determine genetic mechanisms of resistance to biotic and abiotic stresses. Develop molecular markers from segregating populations, to allow introgression of desirable genes into germplasm with other valuable traits. Identify and isolate genes for resistance to pests and pathogens for potential genetic engineering of adapted selections. Create intra-specific, inter-specific, and inter-generic hybrids with superior turfgrass characteristics.
Field data from 2008 and 2009 as well as growth chamber data from 2008 was used to search for regions of the bentgrass chromosomes that contribute to heat and drought tolerance in experimental populations. The analysis identified 7 linkage groups that provide some level of tolerance to these important stresses. Future work will further refine these chromosome locations and the level of importance each plays in heat and drought tolerance. The goal is to improve the speed and accuracy of selection for these important traits.
Plants from and experimental creeping bentgrass mapping population were established and inoculated with Sclerotinia homoeocarpa at the University of Maryland turfgrass research center, College Park, MD. Extensive disease development occurred for the second year and clones with the highest levels of resistance were selected for further evaluation. The most resistant and some selected susceptible clones are being inoculated with S. homoeocarpa and Rhizoctonia zeae. Infected tissue is being harvested to evaluate gene expression that takes place during infection by these two important turfgrass fungal pathogens. The goal is to reduce fungicide inputs on golf courses.
A new type of bentgrass genetic marker was developed using sequence data obtained as part of a bentgrass DNA sequencing collaboration with Rutgers University. The new markers are based on miniature inverted repeat transposable elements (MITEs). MITEs appear to be common in Agrostis and the markers were used to evaluate the genetic diversity of germplasm.
Progress towards the development of a virus-induced gene silencing (VIGS) system for turfgrass continues. We have previously generated infectious cDNA clones of a viral vector, LoLV-US1, which is being developed to study gene expression and VIGS. The LoLV vector has been used to express the Green Fluorescent Protein (GFP) as a model for protein expression, and a fragment of Phytoene Desaturase (PDS) as a model for VIGS. Moderate GFP expression, or localized PDS expression was observed in systemically infected leaves of Nicotiana benthamiana; current efforts are directed towards improvement of VIGS efficacy, and to developing methods for efficient infection of gramineaceous hosts of LoLV. A VIGS vector for turfgrasses will aid in gene discovery and functional genomics for breeding of superior turf types.
Disease resistance genes in turfgrass investigated. The turfgrass diseases dollar spot and brown patch caused by the fungi Sclerotinia homoeocarpa and Rhizoctonia solani are the most widespread fungal diseases of highly managed turfgrass species such as Creeping bentgrass (A. stolonifera). More money is spent to manage these diseases than all other turfgrass diseases combined. Dollar spot and brown patch are widespread throughout the summer months in warm humid areas of the United States, and spray programs are generally scheduled at regular intervals to safeguard against disease establishment. However, these spray strategies can lead to the fungi developing fungicide resistance and this has become a major issue in certain regions of the county. ARS researchers at Beltsville, MD are using new high-throughput DNA sequencing technologies to determine the genes that are important in the interaction of these important fungal pathogens with turfgrass plants. The identification of the genes involved in this interaction has the potential to significantly reduce the amount of fungicides needed to maintain disease free turfgrasses.
Brown, R.N., Barker, R.E., Warnke, S.E., Cooper, L.D., Brilman, L.A., Rouf Mian, M.A., Jung, G., Sim, S.C. 2010. Identification of quantitative trait loci for seed traits and floral morphology in a field-grown Lolium perenne x Lolium multiflorum mapping population. Plant Breeding. 129:29-34.