Mapping and sequence analysis of barley hordoindolines

Abstract

Barley (Hordeum vulgare L.) cultivars vary in traits such as grain hardness and malt quality. However, little is known about the genetic basis of these grain quality traits in barley, while more is known about the basis of grain hardness in wheat (Triticum aestivum L.). Puroindolines are endosperm-specific proteins found in wheat and barley, as well as other members of the Triticeae. In wheat, variation of puroindoline sequence is associated with most of the variability in wheat grain texture. However, no information exists on sequence variation of the barley homologs of puroindolines, the hordoindolines. We have therefore chosen to isolate and characterize the hordoindoline (hin) sequences of eight North American barley cultivars. The barley sequences contain numerous non-conservative amino-acid substitutions relative to their wheat counterparts. However, no significant rearrangements were found in either hinA or hinB of barley. Three hinA and two hinB sequence types were found among the eight barley cultivars examined, indicating substantial allelic variation at this locus. The hinB sequence variability was used to map hinB to the short arm of chromosome 5H in a Steptoe/Morex mapping population, which is coincident with the previously mapped location of hinA and Gsp (grain-softness protein). This chromosomal location also coincides with a small barley malt-extract QTL, suggesting that hordoindoline sequence variation may play a small role in barley grain quality. Efforts to correlate barley seed textural differences and malting quality with hordoindoline sequence type are ongoing.