ARS | Publication request: FINE STRUCTURE MAPPING OF THE BARLEY CHROMOSOME 1 CENTROMERE REGION CONTAINING MALTING QUALITY

Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 19, 1997
Publication Date: N/A

Interpretive Summary: Until recently, breeders have produced improved malting barleys by interbreeding barleys containing good genes and hoping that those genes would be combined in the new barley so that its malting quality was better than that of either parent. This technique has led to the production of greatly improved malting barleys, but it is not a very efficient method. To improve the efficiency of developing improved barleys, we need to determine exactly where the good malting genes are located on the barley chromosomes, so that breeders will know exactly which portions to use to prepare barleys with improved characteristics. Recently, we determined the general locations on the barley chromosome where genes controlling the most important quality traits of malting barley are located. However, we still needed to know more precisely where these genes were located. We have, therefore, now prepared barley lines containing chromosomes that are identical except in very small areas of their structures. By comparing the malting qualities of these slightly modified lines, we have more precisely determined where the genes controlling various malting quality characteristics were located. This knowledge will allow barley breeders to more specifically select the chromosomes areas that contribute good malting quality and will allow them to more quickly, easily and efficiently develope improved barleys for the brewing and other industries.

Technical Abstract: Current techniques for quantitative trait locus (QTL) analyses provide only approximate locations of QTL on chromosomes. Further resolution of these QTL regions is often required for detailed characterization. An important region containing malting quality QTL on barley (Hordeum vulgare L.) Chromosome 1 was previously identified in a Steptoe x Morex cross. This region contains two putative overlapping QTL and each QTL effects malt extraction percentage, alpha-amylase activity, diastatic power, and malt beta-glucan content. This study was to fine structure map this complex QTL region to determine whether these two putative overlapping QTL are really one QTL. Also, we needed to know whether the apparently overlapping QTL are due to one or several genes. A high resolution map in the target region was developed that spans approximately 27 cM. Isogenic lines were created in a Steptoe background that differed only in the region of the QTL of interest. Thirty two different recombinants were identified, of which eight were selected for field testing at three locations. Additive effects on malt quality parameters were calculated based on malting data. By comparing the additive effects among the lines carrying different Morex fragments, multiple QTL for malt extract, alpha-amylase and diastatic power were identified and resolved into 1-8 cM genome fragments. One significant QTL x environment interaction and one possible epistatic interaction were discerned.