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United States Department of Agriculture

Agricultural Research Service

Research Project: Mitigating Insect Herbivory of Warm-Season Bioenergy Grasses – Getting Ahead of the Curve

Location: Grain, Forage & Bioenergy Research

2011 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

Significant parts of the research are being conducted by University of Nebraska cooperating scientists who are being funded via a subsidiary grant (Project 5440-2100-028-09G).

This work is being performed through a USDA/NIFA competitive grant awarded in October 2010 with an official start date of February 1, 2011 through January 31, 2015. For FY 11, both laboratory and greenhouse experiments were conducted. All team members were cognizant of the planned experiments and had approved implementation. Communication was by email and telephone between the ADODR and appropriate project personnel at distant locations (University of Nebraska-Kearney; University of Nebraska -Panhandle Research & Extension Center, Scottsbluff; University of San Diego) and by in-person meetings for project personnel located in Lincoln, NE. One team meeting of all personnel was held in Lincoln on June 21, 2011.

Greenhouse experiments were conducted to assess the resistance/susceptibility of 5 different switchgrass tetraploid populations to insect damage by greenbugs and the common chinch bug. These experiments were performed with plants at the one leaf and two-leaf stage. Experiments are in the process of being repeated. Consistent damage by greenbugs was observed in two populations and consistent resistance was observed in one population. Limited or no damage was seen in plants challenged with chinch bugs. Immediate work at Lincoln will use greenbugs to obtain plant tissues for a number of downstream uses including microscopy, biochemistry and RNA studies. Work is being conducted (July 2011) at the University of Nebraska -Panhandle Research & Extension Center, Scottsbluff to assess the response of switchgrass to challenge with a variety of aphids.

Laboratory experiments have focused on the cloning of a cationic plant peroxidase that appears to be associated with stress responses in switchgrass plants. The cDNA for this enzyme has been cloned and is being readied for generating recombinant protein for eventual production of antibodies. Antibodies have been made to a switchgrass hemoglobin. Antibodies will be used to understand changes in the physiological status of plants challenged with insects.

These laboratory and greenhouse experiments will serve as a foundational base for achieving goals stated in Objectives 1 and 2.


Last Modified: 7/28/2014
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