Location: Wheat, Sorghum and Forage Research2013 Annual Report
1a. Objectives (from AD-416):
Sustainable production of switchgrass and other bioenergy grasses will require effective pest management. Currently we know little about the potential insect pests of the tetraploid switchgrass genotypes that are being developed as bioenergy cultivars for the Central USA. Our prior experience with greenbug-sorghum and chinchbug-turfgrasses interactions indicates that insect pests will eventually emerge on switchgrass fields. Identification of potential insect pests and detailed characterization of the plant-insect interaction will better enable us to address emergent insect pests in switchgrass production fields. Additionally, it is unclear how manipulation of plants for improved quality (for example lower lignin) will affect plant resistance to insect herbivory. Our collaborative team has recently identified the yellow sugarcane aphid, chinch bugs, and greenbugs as potential pests of switchgrass. With our combined expertise in plants and insects, we are uniquely positioned to provide significant new information that will serve as the foundation for long-term sustainable pest management strategies. The research goals of this 5 year project are to identify plants with enhanced resistance to sucking insects using defined populations of switchgrass, improve our understanding of the mechanisms, genes, proteins and metabolites contributing to the resistance, and develop sustainable pest management strategies through endogenous plant resistance. Our long-term research goals are to significantly impact the development of bioeneregy grasses with enhanced resistance to biotic stress that offer improved environmental safety and reduce human health risks. Specific objectives: 1: Develop efficient phenotyping tools for insect resistance of switchgrass and other tall perennial grasses. 2: Understand insect resistance mechanisms among defined switchgrass populations. 3: Obtain biochemical, physiological and anatomical insights into insect-bioenergy grass interactions. 4: Define transcriptional and metabolic changes occurring in switchgrass genotypes with varying levels of insect resistance. 5: Utilize methods in RNA profiling of insects to uncover key transcriptional regulatory mechanisms that govern host range in grass-feeding insects.
1b. Approach (from AD-416):
We will take defined populations of switchgrass and investigate plant and insect responses with a wide array of complementary tools, including characterization of the resistance responses using antixenosis, antibiosis, and tolerance methodologies. Functional genomic tools will be used to define biochemical, physiological, metabolic and molecular plant defense mechanisms, and take advantage of existing switchgrass molecular resources and the pending release of a draft version of the switchgrass genome, and exploit its synteny with sorghum to identify potential genes. Traditional and molecular methods such as high-throughput DNA sequencing will be used to decipher fitness parameters for the different insects.
3. Progress Report:
The goal of this project performed through a USDA/NIFA competitive grant is to understand plant responses to herbivory to piercing-sucking insects to ultimately develop switchgrass plants with improved insect resistance. Plant identified as resistant or susceptible in greenhouse screens using two aphids, greenbugs and yellow sugar cane aphid were clonally propagated. One clone of resistant and susceptible plants from two different populations of switchgrass (cv Summer and Kanlow) were subsequently transferred to isolation crossing blocks in the field. Each block contained 10-15 plants of a single population belonging to a single category (resistant or susceptible). Plants will be allowed to intermate and seeds (if available) will be harvested on an individual plant basis for further insect feeding and genetic trials at the end of the 2013 growing season. In other experiments, leaves from cv Summer plants challenged with greenbugs were harvested. RNA extracted from leaf tissues has been submitted for DNA sequencing using a next-generation sequencing platform (Illumina Hi-Seq 2000, University of Nebraska-Medical Center). Other work is underway or planned for completion within FY13 to address biochemical and anatomical changes associated with aphid feeding of switchgrass plants. Insect-related work focused on obtaining the microRNA (miRNA) profiles in the greenbug and the yellow sugarcane aphid. These data are currently being analyzed using bioinformatic tools. Significant headway has been made on the addressing the project objectives 1-4. Some work has been started on objective five. Communication was by email and telephone between the ADODR and appropriate project personnel at distant locations (University of Nebraska-Kearney; University of Nebraska-Omaha; University of Nebraska -Panhandle Research & Extension Center, Scottsbluff; University of San Diego) and by several in-person meetings for project personnel located in Lincoln, NE. One team meeting of all personnel was held in Lincoln on June 21, 2013. All team members were cognizant of the planned experiments and had approved implementation.