The Hunt for Green Every April: Factors Affecting Fitness in Switchgrass
Investigators: G. Sarath, K.P. Vogel, C.M. Tobias, S. Madhavan, and P. Twigg
Institutions: USDA-ARS, Lincoln; USDA-ARS, Albany; University of Nebraska, Lincoln; and University of Nebraska, Kearney
Non-Technical Summary: Perennial biomass energy crops such as switchgrass have significant net energy advantages because annual planting each spring is not required and they can be grown on marginal cropland. Switchgrass plants need to survive both repeated harvests and winters in the production fields for 10 or more years. Winter hardiness and survival are therefore critical traits. However, the physiological and genetic factors underlying perenniality and winter hardiness (fitness) in perennial grasses such as switchgrass are not known. This grant seeks to understand winter survival in switchgrass populations and individual plants specifically selected for greater yields and with known differences in winter survival by studying molecular events occurring in the crowns and rhizomes during two growing seasons and winters.
Objectives: The objectives of this proposal are (1) To utilize novel genomic and biochemical tools to investigate molecular mechanisms underpinning nutrient partitioning and remobilization in crowns and rhizomes of switchgrass cultivars with divergent winter hardiness. (2) To use high-throughput DNA sequencing to query transcript abundance (levels of gene expression) in specific populations of switchgrass plants during regreening and dormancy. (3) To study the genetic variation (extent of linkage disequilibrium in populations) and eventually develop genetic markers for cold-adaptation and fitness traits in switchgrass plants being developed for the Central and Northern United States that show significant hybrid vigor (heterosis).
Approach: Obj. 1. Switchgrass plants of five different cultivars or experimental strains that differ in their cold hardiness and fitness parameters will be transplanted into field nurseries in the establishment year. The following two years, crowns and rhizomes will be harvested from these plants at specific times for genetic (high-throughput pyrosequencing; 454 transcriptomics) and metabolite analyses. Additional plants will be subjected to isotope-tracer experiments using stable isotopes for carbon (C-13) and nitrogen (N-15) to query nutrient recycling over two growing seasons as affected by the genetic background of the plants. These data will permit improved insights into the molecular and physiological events that impact perenniality and fitness in switchgrass.
Obj. 2. Using genomic approaches (454 pyrosequencing and bioinformatics), we will discover additional genes impacting fitness using individual plants from switchgrass populations divergently selected over ~30 years for ruminant digestibility that resulted in strains differing significantly in lignin concentration and winter survival.
Obj. 3. We will attempt to uncover marker-trait associations (based on genes uncovered in Obj.1 and Obj. 2) that will form the basis of a marker-assisted selection program that can be used to reduce the time and expense of phenotyping in the breeding process.
Name: G. Sarath