2009 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.
Growth chamber studies were conducted with the objectives of evaluating variations in heat tolerance for a mapping population of creeping bentgrass segregating for disease resistance and identifying QTL markers associated with heat tolerance utilizing the available linkage maps. The ultimate goal is to dissect the complex inheritance of quantitative traits associated with drought and heat tolerance and to identify QTL markers, which could potentially be used in molecular marker- assisted selection for improving drought and heat tolerance in creeping bentgrass. First year data has been collected and is being analyzed.
Plants from an 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 has been observed and initial ratings show significant disease resistance differences exist between members of the population. Data analysis indicates the molecular markers linked with Sclerotinia resistance in Wisconsin do not predict resistance in Maryland. Additional inoculations and ratings are being conducted to confirm the first year findings.
A new type of Bentgrass genetic marker was developed using sequence data obtained as part of a Bentgrass DNA sequencing collaboration with Rutgers University. MITE markers were developed by searching the available Bentgrass sequence for sequences having MITE-like characteristics such as small size (< 500 bp), target site duplications, and terminal inverted repeats. Several hundred Mite-like sequences have been identified in Bentgrass and approximately 10 were chosen for further analysis. Primers were designed for MITE display and the resulting MITE display markers were shown to segregate in expected ratios in an experimental Bentgrass mapping population.
We have previously generated infectious cDNA clones of Lolium latent virus-US1, which is being developed for use as a viral vector for gene expression and virus-induced gene silencing. The LoLV vector has been used to express the Green Fluorescent Protein (GFP) as a model for protein expression, and separately a fragment of Phytoene Desaturase (PDS) as a model for gene silencing. Moderate GFP expression, or localized gene silencing, was observed in systemically infected leaves of Nicotiana benthamiana; current efforts are directed towards improvement of gene silencing efficacy, and to developing methods for efficient infection of gramineaceous hosts of LoLV. A silencing vector for turfgrasses will aid in gene discovery and functional genomics for breeding of superior turf types.
Agrostis species relationships. Creeping bentgrass (Agrostis stolonifera L.) is the premier turfgrass species used on golf course putting greens, fairways, and tees. One of the difficulties in determining the progenitors of the cultivated bentgrasses is the lack of accurate ploidy determinations for many of the Agrostis accessions maintained in the National Plant Germplasm System (NPGS). An ARS scientist working in Beltsville, MD analyzed 75 Agrostis accessions representing 15 distinct species along with two Apera and four Polypogon accessions using flow cytometry and 1,309 DNA markers. Cluster analysis clearly separated the common turf-type Agrostis species into distinct groups. The inclusion of previously understudied species within these groups offers insights into the genomic origins of creeping bentgrass that will be useful in future breeding efforts. In addition, the data suggest a narrowing of the genetic diversity within cultivated creeping bentgrasses.
Zhang, C., Fei, S., Warnke, S.E., Li, L., Hannapel, D. 2009. Identification of genes associated with cold acclimation in perennial ryegrass.. Journal of Plant Physiology. Available at http://dx.doi.org/10.1016/j.jplph.2009.03.001.