Genetic resources for intermediate wheatgrass

Authors: Larson, Steven; Jensen, Kevin

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/15/2012
Publication Date: 7/16/2012
Citation: Larson, S.R., Jensen, K.B. 2012. Genetic resources for intermediate wheatgrass. Meeting Abstract.

Interpretive Summary:

Technical Abstract: Intermediate wheatgrass (Thinopyrum intermedium) is a perennial Triticeae species, closely related to wheat, barley, and rye. Intermediate wheatgrass is a highly productive and palatable forage grass, which is also a potentially useful source of resistance genes for important plant diseases such as Fuarium graminearum head blight and Puccinia graminis stem rusts in wheat. Moreover, there is also considerable new interest in the development and utilization of intermediate wheatgrass as a perennial grain crop or possible new bioenergy feedstock. Thus, gene-specific markers are needed for the breeding and genetic improvement of intermediate wheatgrass for many important uses. Intermediate wheatgrass is a complex allohexaploid, which is thought to contain three distinct subgenomes St, Eb, and Ee from divergent Pseudorogeneria, Th, bessarbicum, and Th, elongatum diploid grasses, respectively. Our objective is to develop expressed gene sequence tag (EST) markers for intermediate wheatgrass and representatives of the possible diploid ancestors of intermediate wheatgrass. A total of 27,273 EST unigenes were previously sequenced by Sanger technique from diploid Pseudoroegneria (St genome) with an average size greater than 1,000 bp. A total of 451 out of 1083 EST-SSR markers were polymorphic in a test of two different Pseudoroegneria plants and showed genetic map specifically to the St genome of allotetraploid Elymus, which also contain the divergent H genome of genus Hordeum. More recently, nearly 1.4 million RNA-seq reads with an average length of 427 bp were obtained from transcriptome sequences of hexaploid intermediate wheatgrass (EeEbSt genomes) and two other possible diploid ancestors of intermediate wheatgrass, Th. bessarbicum (Eb), and Th.elongatum (Ee) using next-generation techniques. These DNA sequences were assembled into 71,300 contigs with an average size of 667 bp and 123,200 unmatched reads with an average size of 373 bp. The sequence contigs contained 3,400 possible single-nucleotide polymorphisms (SNPs) in Th. bessarbicum (Eb), 43,000 possible SNPa in Th.elongatum (Ee), and 50,500 possible SNPs in intermediate wheatgrass. These DNA sequences and putative polymorphisms provide a rich and diverse source of gene-specific markers for the three putative subgenomes of intermediate wheatgrass.