Location: Forage Seed and Cereal Research2012 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.
3. Progress Report:
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 global markets. Unfortunately, genetic information and molecular resources needed to improve forage and turf grass systems are lacking. An approach to disrupt specific gene function in forage and turf grass species has been demonstrated and is being tested in grasses. Transformation systems for Brachypodium and Lolium have been established. A series of genes expressed in response to salt stress was sequenced and annotated and genes that regulate the expression of specific DNA sequences in response to oxidative stress have been identified. Forage and turf grasses are repeatedly cut or grazed upon by animals, but there is little information on the physiological and molecular responses to repeated wounding in these grasses. We identified an intermediate signaling protein and pathway that is activated when grasses are wounded or cut, and in response to heat and salt stress. We sequenced a wound expression library from Lolium temulentum and showed that specific gene sequences are activated by wounding both locally and in the systemic unwounded tiller of the grass plant. This research will enable further development of genetic approaches to improve yield and persistence of forage grasses used for livestock and bioenergy. ARS scientists at Corvallis, Oregon, and Oregon State University showed that the Germination Arrest Factor (GAF), a bioherbicide produced by the soil bacterium Pseudomonas fluorescens also inhibits the growth of Erwinia amylovora, the bacterium that causes fire blight in apple and pear crops. This discovery demonstrated that GAF has utility as a biological control agent. The growth inhibition also provides a convenient means for detecting the presence of GAF in bacterial cultures. Genetic regions in Pseudomonas fluorescens that regulate GAF biosynthesis were identified, an important step in developing bacteria that produce commercially significant quantities of the bioherbicide. Genetic resistance is the best long-term approach to managing stem rust, the most significant disease problem for seed production crops of perennial ryegrass and tall fescue. Resistance has been difficult to incorporate due to the lack of information about nature and inheritance of resistance genes in these out-crossing species. We determined that there are genes for partial resistance that result in a greatly reduced "infection efficiency" and that this resistance is heritable. We also discerned the approximate location of these resistance genes on two chromosomes of perennial ryegrass, and detected nearby sections of DNA that might be useful as markers for plants carrying the resistance genes in future plant breeding efforts to enhance resistance.
Halgren, A.B., Azevedo, M.D., Mills, D.I., Armstrong, D., Thimmaiah, M., Mcphail, K., Banowetz, G.M. 2011. Selective inhibition of Erwinia amylovora by the herbicidally-active Germination-Arrest Factor (GAF) produced by Pseudomonas bacteria. Journal of Applied Microbiology. 111: 949-959.