INVESTIGATORS: Kresovich, S.; Paterson, A.H.; Feltus F.A.
INSTITUTIONS: University of South Carolina; University of Georgia; Clemson University
NON-TECHNICAL SUMMARY: Our goal is to build the germplasm, breeding, genetic, and genomic foundations necessary to optimize cellulosic sorghum as a bioenergy feedstock. We define cellulosic sorghum as an annual or perennial form that is bred and selected to maximize carbon (energy) accumulation per unit time, land area, and/or production input (water, nutrients, pesticides, etc.). The ideotype will be extremely tall, heavy tillering, large-barreled, dry stemmed, photoperiod-sensitive material that aggressively regrows in environments with milder winters (southern U.S.).
OBJECTIVES: The specific objectives of the proposed research are: (1) to develop ten nested association mapping populations (NAMs) and a diversity panel necessary to dissect the genetic bases of carbon accumulation and partitioning of cellulosic sorghum; (2) to phenotype these NAMs and diversity panel for patterns of carbon accumulation and partitioning and to correlate these traits with DNA sequence variation that will underlie future breeding/genetic studies; (3) to lay the foundation for integrating genomic selection and other genomics-based strategies into cellulosic sorghum breeding programs; and (4) to identify and create cellulosic male-sterile (A lines), maintainer (B lines), and restorer (R lines) germplasm necessary to exploit heterosis specifically targeted at energy production.
APPROACH: We will test the hypothesis that parallel evolution of and selection for cellulosic sorghum in different botanical races may have involved convergent mutations or introgressions, with the result of a high level of correspondence of QTL locations in crosses involving different botanical races. This implies that the genetic control of the traits fundamental to this ideotype may be relatively simple, and quickly identified to expedite marker-based selection. We also will implement a systems biology approach toward tests of multiple hypotheses that specific molecular pathways are underlying QTLs sets by fitting de novo generated sorghum gene-gene coexpression interactions (and their predicted function) to QTLs on a trait-by-trait basis. In this way, we will identify groups of candidate genes with evidence that makes them priorities for functional validation through association genetics, reverse genetics, or transgenic approaches. Synergistically to this effort, ongoing DOE JGI community sequencing and NSF-BREAD genotyping projects will provide the fundamental information, pipeline, and associated database for us to identify the required SNPs. This project also will complement a NAM set being developed for grain sorghum, with ten additional populations that address traits of singular importance to cellulosic sorghum, using a common parent (‘Grassl’) and other lines exhibiting wide variation in genetic background, geographic origin, biomass composition, and agronomic phenotype. Lastly, products (A, B, and R lines) critical to successful breeding of cellulosic hybrids will be developed. Heterosis will impact yield and composition in manners for which we expect to provide diagnostic DNA markers, while simultaneously advancing the crop for use by the U.S. seed industry.
Name: Kresovich, S.