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Analysis of two switchgrass ecotypes indicates genetic diversity of a disease resistance gene class that contains a serine-threonine protein kinase

Lorna Nissen: The University of Georgia

<div>Switchgrass (<em>Panicum virgatum</em> L.) is a perennial warm-season grass indigenous to tall grass prairies in North and Central America. The United States Department of Energy chose switchgrass as a potential bioenergy crop for ethanol production due to its rapid growth, high biomass yield, and ability to be cultivated in poor soil and climate conditions and with low inputs. Upland and lowland are major switchgrass ecotypes that have emerged through natural selection. Switchgrass has not been grown in monoculture, so it is not known which pests and pathogens will affect production. The nucleotide binding site (NBS)-leucine-rich repeat (LRR) class of resistance (R) genes is the largest known class of R-genes that plants use to detect the presence of pathogens and induce defense responses. This project has three major objectives: 1) Identify and sequence resistance gene homologues (RGHs) in the two switchgrass ecotypes, 2) Determine the number of RGH haplotypes in the ecotypes, and 3) Analyze the genetic diversity of RGHs in the ecotypes. In this study, a PCR-based approach was used to characterize the genetic diversity of the NBS-LRR RGHs in 37 switchgrass populations derived from 16 states. PCR-amplified RGHs were cloned and sequenced. Phylogenic analysis of RGHs in the two switchgrass ecotypes indicates 1) high genetic diversity, and 2) the predominant class of R-genes contains an LRR receptor-like serine-threonine protein kinase.</div>