INVESTIGATORS: Serge Edmé (PI), Nathan Palmer, Satyanarayana Tatineni, Gautam Sarath, Robert Mitchell, Gary Yuen
INSTITUTIONS: USDA ARS Grain, Forage and Bioenergy Research Unit (GFBRU), Lincoln, NE; University of Nebraska, Lincoln
PROJECT SUMMARY: Establishing switchgrass as a key component of the bioenergy industry in the US will require cultivars to have the right suite of genes for high biomass and ethanol yield with good quality profiles and durable resistance to diseases. Because switchgrass is susceptible to a number of fungal (Puccinia emaculata and Uromyces graminicola) and viral (Panicum mosaic virus) pathogens, yield stability and biofuel output under biotic stress are important selection criteria for biofuel feedstock improvement.
This project leverages the differential performance of a lowland (‘Kanlow’, resistant) and upland (‘Summer’, susceptible) cultivar under rust and mosaic disease pressures to provide the genetic, molecular, physiological, and transcriptomic bases for imparting durable rust and viral disease resistance to switchgrass. Progeny populations derived by crossing Kanlow (male) with Summer (female) plants possess high biomass yields and intermediate resistance to infection, indicating significant opportunity to improve disease resistance in these high-yielding populations. The specific objectives are: (1) Understand the genetic and genomic bases of pathogen response in regionally adapted upland and lowland switchgrass breeding populations with contrasting disease symptoms under field conditions, (2) Dissect the molecular underpinnings of why ‘Kanlow’ has broad resistance or tolerance to pathogens, and (3) Discover the molecular differences that permit systemic viral infections in some switchgrass plants, but not in other genetically-related plants.
Genomic selection will be applied across three generations of a Summer x Kanlow breeding population using DArTseq (DArT+SNP markers) to develop prediction models for yield (biomass and quality) and disease traits based on genetic and genomic breeding values. The functional transcriptional networks underpinning the broad rust and viral disease resistance or tolerance in the population will be studied. RNAseq data will be collected to interrogate the transcriptional changes underlying defense responses in switchgrass, based on the overall and specific differences in gene expression in Kanlow and Summer.
These studies will be complemented by engineering viral genomes with fluorescent markers to visualize viral movement and pathogenesis in plants, developing antibodies to coat proteins to detect virus in field-grown samples, and by using recombinantly-expressed viral proteins to identify interacting plant proteins that are crucial for the spread of infection. The identification of disease and yield-related genic regions and a better understanding of the transcriptional networks underlying disease resistance/tolerance will facilitate pyramiding the genes into released cultivars for durable resistance and ultimately improve the bioenergy potential of switchgrass through breeding and selection.
Name: Edmé, Serge