2010 Annual Report
1a.Objectives (from AD-416)
Provide the seed industry with improved grass germplasm and management practices that reduce the impact of salinity, weeds, and diseases on seed quality and profitability. Identify bioactive compounds and genes that mediate the response of Lolium and Festuca to salinity related stress. Develop approaches to characterize, select and utilize components of host genetic resistance to pathotypes of the stem rust pathogen in Lolium. Determine whether a small molecular weight bioherbicide, produced by selected naturally occurring soil rhizobacteria (Pseudomonas sp.), that inhibits the germination of Poa annua can reduce the impact of this weed on seed production and turf quality. Develop molecular methods and tools that facilitate germplasm improvement for diverse uses. Develop a means to improve gene stability and minimize escape of transgenes in forage and turf grasses (Lolium sp.). Characterize genetics of host resistance to stem rust, and develop molecular markers for stem rust resistance in Lolium. Identify candidate genes that can be exploited to increase biomass of cool-season grass plants (Lolium sp.) to improve forage quality and source material for bioenergy production.
1b.Approach (from AD-416)
Conduct complex basic and applied research to improve the production and utilization of seed and grain from forage and turf seed cropping systems which include wheat. Traditional breeding and molecular genetics will be used to identify the genetic basis for stem rust resistance, factors that impact seed quality, flowering, and abiotic stress tolerance. Develop molecular and traditional approaches useful for altering plant developmental pathways and plant structures, and enhancing forage quality in end-use environments that differ from the seed-producing region. Bioherbicides that reduce weed presence in seed production and turf environments will be identified and characterized to enable commercialization of new products. Formerly 5358-21000-012-00D and 5358-21000-018-00D(2/01), 5358-21000-028-00D. FY03 Program Increase $100,592. FY04 Program Increase $120,784. Add 1 SY. Formerly 5358-21000-032-00D (5/08).
Stress tolerance, disease resistance and effective weed control in forage and turf grass seed production systems are needed to ensure a sustainable supply of these crops for domestic and international markets. Unfortunately, there is lack of genetic information and molecular resources available for development of approaches to improve forage and turf grass systems. In order to develop molecular resources, the complete genome of the strain of Pseudomonas fluorescens that secretes a germination arrest factor (GAF) with herbicidal activities against an array of grassy weeds was sequenced. This sequence information permits direct comparison of gene sequences in closely related strains of the bacterium that do not produce GAF, enabling us to understand how GAF production is regulated. Currently research is underway to isolate and identify the genetic factors involved in GAF biosynthesis.
One approach to genetically improve stress tolerance, resistance and other characteristics of grasses is the introduction of novel genes into plants. Research on approaches to transform and regenerate transgenic grass plants is on-going. A rapid transformation system of tall fescue grass suspension cultures was developed. Two distinct transformable tall fescue cell suspension culture lines with different degrees of salt tolerance were developed. These cell lines coupled with the rapid transformation system will facilitate the assessment of putative salt tolerance genes. A protein that putatively regulates gene activation of salt tolerant genes was introduced into these cell lines and experiments are currently underway to assess its effects. A composite salt stress gene-expression library from a model grass species was sequenced. Annotation and development of a salt stress reference library for forage and turf grasses is currently under way, this database will be utilized in future salt stress gene expression studies to identify and characterize the molecular components associated with salinity stress tolerance. Research has recently identified the activation of an intermediate signaling protein and pathway in grass plants that are exposed to salt or wounding stress. This signaling protein is activated systemically in the plant. Research is on-going to determine the signal that is being generated and how it is perceived in the plant.
Stem rust disease continues to have a negative impact on the yield and quality of perennial grasses and basic information on the disease process is needed to develop management practices and improved resistance for the disease. The identification of different single pustule isolates of stem rust pathogens that display variable affects on different accessions of grasses coupled with the identification of grass plants with variable resistance to stem rust, has provided the tools necessary to dissect and identify genetic regions in the host plants controlling resistance to different genetic strains of the pathogen. Currently genetic markers are being used to identify these regions in the target grass genome. Collectively this research provides the basis for improved survivability and yield in forage and turf grass systems.
Demonstrated existence of genetic strains of ryegrass stem rust. Genetic variants of the fungus that causes stem rust disease of ryegrass were demonstrated to differ in their disease-causing ability. ARS scientists in Corvallis OR purified individual strains of the fungus and showed that some strains could cause disease on host plant genotypes that were completely resistant to other strains. This discovery provides information and experimental materials to conduct research on genetic loci for stem rust resistance in ryegrass, which will benefit ryegrass seed production and also provide information useful for stem rust resistance in threatened cereal crops such as wheat and barley.
Identified an early signaling component utilized by forage and turf grasses to sense their environment when exposed to wounding conditions. Grasses are continually cut for hay and grazed by livestock, however very little is known concerning the molecular events that occur in grass plants as a result of wounding. ARS scientists in Corvallis Oregon identified the activation of a signaling protein in response to wounding in various grass plants. It is not known if the activation of this signaling protein in response to wounding induces defense compounds and genes or if it stimulates growth pathways to replenish lost tissues. This research provides the first step towards our understanding of these molecular signaling events and networks, which in the long term have the potential to improve and increase the yield, sustainability and quality of grass feed stocks utilized for livestock and for biofuel production.
Development and genetic transformation of tall fescue cell lines. Development of stable transgenic grass plants to access gene function can be difficult and time consuming. ARS scientists in Corvallis, Oregon have developed a rapid transformation system of tall fescue grass suspension cultures that display different degrees of salt tolerance. The development of these cell culture lines and transformation system will facilitate the identification and assessment of putative salt tolerance genes that will have the potential to improve stress tolerance in forage and turf grasses.
Discovered that the bioherbicide GAF inhibits the growth of a plant pathogen. The bioherbicide that arrests the germination of grassy weeds (GAF) also was found to inhibit the growth of a bacterium that causes fire blight in apples and pears. ARS scientists in Corvallis Oregon, along with cooperators from Oregon State University placed small amounts of GAF on plates containing cultures of the fire blight bacterium and found that GAF prevented growth of the bacterium. This discovery may provide a means to develop a biological approach to controlling this disease in apples and pears. The biological control approach has the potential to reduce the amount of pesticide used for disease control in these food crops.