Linkage mapping and nucleotide polymorphisms of the 6-SFT gene of cool-season grasses

Fructan plays an important role as an alternate carbohydrate and may contri bute to drought and cold-stress tolerances in various plant species. The ge ne coding for sucrose:fructan 6-fructosyltransferase (6-SFT; EC 2.4.1.10), an enzyme that catalyzes the formation and extension of beta -2,6-linked fr uctans (levans), is important to fructan synthesis in many cool-season gras ses, including cereal species. In this study, we compared a conserved seque nce from the 6-SFT gene in barley with comparable sequences in 20 other coo l-season grasses. We detected several DNA length polymorphisms, including v ariations in one simple-sequence repeat (SSR) in a 6-SFT intron of the barl ey cultivars Steptoe and Morex. Using the 'Steptoe' x 'Morex' doubled-haplo id mapping population, the 6-SFT gene was genetically mapped to the distal region in the short arm of barley chromosome 1 (7H), where it is closely li nked with trait locus Rpg1. Primers designed from other conserved regions o f the barley 6-SFT gene successfully amplified 351- or 354-bp sequences of this gene from diverse cool season grass species. Sequence identities of th e PCR products were greater than 80% among the 21 species. Phylogeny, as de termined using these DNA sequences, is similar to that obtained from rDNA I TS sequences, and congruent with our current knowledge of genome relationsh ips.