DNA markers and gene expression polymorphisms associated with growth habit quantitative trait loci in Leymus wildryes.

摘要

The genus Leymus includes about 30 long-lived perennial Triticeae grasses distributed throughout cold and/or semiarid regions of Americas, Europe, and Asia. Leymus cinereus and L. triticoides display divergent growth habit adaptations to different microenvironments in western North America. L. cinereus, a tall caespitose bunch grass, is commonly found near mountain and foothill waterways. L. triticoides, a relatively short rhizomatous grass, is restricted along stream banks or saline wetlands. Subterranean tiller and rhizome buds appear similar but display different responses to gravity and other cues governing branch angle and overall growth habit. In previous studies, two full-sib mapping families (TTC1 and TTC2) derived from L. triticoides x L. cinereus hybrids displayed growth habit QTLs on homoeologous regions of LG3a and LG3b in both allotetraploid families, suggesting that linkage group 3 controls much of the difference in rhizome spreading between two species. These TTC1 and TTC2 families segregated for different regions of the putative growth habit QTL. Advanced backcross families were derived from TTC1 and TTC2 donor parents based on marker genotypes. Informative DNA markers were detected using 17 AFLP primer combinations in advanced backcross populations. Circumference QTL was localized to a 30 cM region on group LG3a of advanced backcross populations. The genetic map order of 23 LG3a and 17 LG3b Leymus EST or STS markers was strictly collinear with homologous sequences on rice chromosome 1. Mapping of three EST-SSR sequences on both LG3a and LG3b confirmed their homoeology. Overall gene expression patterns of negatively orthogeotropic (NOGT) and diageotropic (DGT) subterranean meristems were remarkably similar, confirming that Leymus orthogeotropic and diageotropic subterranean meristems develop from truly homologous meristems. One marker obtained from differentially expressing genes was genetically mapped on Leymus LG3. Although NOGT and DGT meristems eventually show substantial differentiation, these results identified a relatively small number of gene expression polymorphisms associated with early developmental differences involving the tropic differences between NOGT and DGT meristems.