Genetics and mapping of quantitative trait loci of feed quality-related traits in barley (Hordeum vulgare L.)
Abdel-Haleem, Hussein Ahmed.
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The agricultural sector continues to outpace other industries in Montana. Cattle and calf production are 50% of Montana's agricultural cash receipts. Based on its moderate protein content and lower price, barley is an alternative to corn in finishing cattle diets. Most of Montana barley is produced for animal feed. The objective of this project is to encourage calf producers to retain more feeder calves in Montana by developing improved value feed barley for both the barley grower and cattle producers. Barley has been criticized for cattle feed because of its rapid digestion in the rumen, which can result in many digestive disorders such as bloat and lactic acidosis in cattle fed on high barley diets. A potential approach to limit this problem associated with feeding barley is to select barley cultivars that have a slower rate of digestion in the rumen. Selection of barley grain for low dry matter digestibility (DMD), low acid detergent fiber (ADF) content and high starch content should allow progress in breeding for improved feed quality. The aim of the current thesis is to use DNA marker technology coupled with different barley mapping and validation populations and DMD assays to identify the chromosomal location of genes modifying grain composition and digestibility. The obtained QTLs can be used to transfer the low DMD trait from exotic germplasm resources to high yielding cultivars. The largest QTL impacting DMD that we detected in this project resides on barley chromosome 2H very close to Vrs1. That gene also impacts plant and seed development. The strong correlation among DMD, particle size and yield and the overlapping QTLs which are controlling the variation in these traits around Vrs1, may be due to pleiotropic effects or closely linked QTLs. If this is a pleiotropic effect, gene transfer into 2-rowed backgrounds will be impossible. If, however, linkage is the cause of the association between Vrs1 and DMD-QTL, then larger mapping populations should permit us to better map the gene and identify useful recombinants.