Submitted to: Journal of Heredity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 23, 2013
Publication Date: June 12, 2013
Citation: Larson, S.R., Kellogg, E.A., Jensen, K.B. 2013. Genes and QTLs controlling inflorescence and culm branch architecture in Leymus (Poaceae: Triticeae) wildrye. Journal of Heredity. doi:10.10931/jhered/est/033. Interpretive Summary: Grass flower and stem branches show easily recognizable architectural difference that are often used to identify species. The flower branches of wheat, barley, rye, and 400-500 related wild grasses are usually contracted into a special architectural formation known as a spike with the number of flowering branching points conserved within species and genera. Perennial wildrye grasses are unusual in that the number of flowering branching points varies, flowering branches may extend into an open panicle formation, and vegetative stems may branch into underground rhizomes. Basin wildrye and creeping wildrye show distinct differences in flower branching formation, number of flowering branching points, and distance of underground rhizome spreading. Chromosome regions controlling these traits were identified in two experimental populations derived from the interspecific hybrids of basin wildrye and creeping wildrye using a genetic map with 360 expressed gene sequences from wildrye stem and rhizome branches. Alignments of genes, mutations, and chromosome regions controlling flower and stem branching differences between basin wildrye, creeping wildrye, and other grass species including wheat and barley were identified using a complete DNA reference sequence from a model grass species known as purple false brome. Evidence suggests that genes controlling flower and stem branch architecture differences between basin wildrye and creeping wildrye are conserved among other grasses, modified by natural selection, and useful targets for improving seed and grain yield.
Technical Abstract: Grass inflorescence and stem branches show recognizable architectural differences among species. The inflorescence branches of Triticeae cereals and grasses including wheat, barley, and 400-500 wild species are usually contracted into a spike formation with the number of flowering branches (spikelets) per node conserved within species and genera. Perennial Triticeae grasses of genus Leymus are unusual in that the number of spikelets per node varies, inflorescences may have panicle branches, and vegetative stems may form subterranean rhizome branches. Leymus cinereus and Leymus triticoides show discrete differences in inflorescence length, branching architecture, node number and density; number of spikelets per node and florets per spikelet; culm length and width; and perimeter of rhizomatous spreading. Quantitative trait lock controlling these traits were detectetd in two pseudo-backcross populations derived from the interspecific hybrids using a linkage map with 360 expressed gene sequence markers from Leymus tiller and rhizome branch meristems. Alignments of genes, mutation, and quantitative trait loci controlling similar traits in other grass species were identified using the Brachypodium genome reference sequence. Evidence suggests that loci controlling inflorescence and stem branch architecture in Leymus are conserved among the grasses, governed by natural selection, and possible gene targets for improving seed and grain production.