Genetic Mechanism of Switchgrass Heading Time.

Megan Sue Taylor¹, Xiongwei Zhao¹, Carl-Erik Tornqvist², Paul Grabowski³, Michael Casler³ and Yiwei Jiang¹, ¹Department of Agronomy, Purdue University, West Lafayette, IN, ²Department of Agronomy and DOE Great Lakes Bioenergy Research Center, University of Wisconsin - Madison, Madison, WI, ³USDA Dairy Forage Research Center, Madison, WI

Switchgrass is a native prairie grass that has shown implications in being a valuable bio-energy crop. Switchgrass is capable of surviving a variety of environments, yielding large amounts of biomass. The species has high water use efficiency and requires relatively low amounts of inputs, which makes it a primary candidate for biofuel production. The physiological change from juvenile to reproductive adult can draw important resources away from growth and into producing reproductive structures, thus limiting the growth potential of early flowering switchgrass plants. Delaying the flowering of switchgrass by four to five weeks could increase the total biomass by 30-50%. To develop a rational strategy for creating improved switchgrass with late flowering, it would be beneficial to have a better understanding of the genetic mechanisms that control late floral development in switchgrass. The goal of this project was to examine genetic variation of heading time in four reciprocal crosses of switchgrass populations and to identify the genes associated with the initiation of floral development. Data of heading time were collected from four populations derived from lowland (late flowering) and upland (early flowering) ecotypes in two locations, Lafayette, IN (hardiness zone 5) and Dekalb, IL (hardiness zone 6). The interaction of genotype by environment was explored to determine if location affected the heading time. Large amounts of single nucleotide polymorphisms (SNPs) were obtained by exome sequencing. A genome wide association study (GWAS) was completed and identified an FLOWERING LOCUS T (FT) locus within a region of chromosome 5B at the Lafayette location. A significant SNP was also identified for both locations on chromosome 8A. Transcriptome analysis by RNA sequencing is currently being conducted to identify genes related to heading date. The differentially expressed genes between the early and late heading individuals identified will be compared with genes identified with GWAS results. Identifying genetic variants related to flowering could assist in developing late flowering varieties of switchgrass with high biomass yield.

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