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ARS Home » Midwest Area » Madison, Wisconsin » Cereal Crops Research » Research » Publications at this Location » Publication #73796
Title: GENETIC COMPLEXITY OF THE MALT EXTRACT TRAIT IN BARLEY SUGGESTED BY QTL ANALYSIS

Author
item ULLRICH, S - WASHINGTON STATE UNIV.
item HAN, F - WASHINGTON STATE UNIV.
item Jones, Berne

Submitted to: Journal of the American Society of Brewing Chemists
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Until now, the methods used by breeders to produce improved malting barleys have largely involved interbreeding barleys containing good genes and hoping that those genes would be combined in the new barley in such a way that it's malting quality was better than that of either parent. While use of this technique has led to the production of greatly improved malting barleys, it is not a very efficient method. This paper reports the locations, on the barley chromosome, of genes that control the most important quality trait of malting barley, malt extract. Improved malt extract is notoriously hard to breed for, because it is controlled by several different individual genes. This paper reports where some of the malt extract genes are located relative to other easily detected parts of the barley chromosome. It also reports that most of these genes are located adjacent to, or are the same as, genes controlling other essential malting quality traits. With this knowledge, it is now possible for researchers to select barleys having the easily detected characters. The selected barleys will almost always contain the hard to detect good genes also, because they occupy adjacent areas of the chromosomes. Breeders can now more quickly, easily and efficiently develope improved barleys for the brewing and other industries. 

Technical Abstract: Most economically important traits of crop species are complexly inherited quantitative traits (QT). Trait expression tends to vary continuously due to the fact that the traits are affected by multiple genes (G), the environment (E), and by both G x G and G x E interactions. The development of comprehensive genome maps and of quantitative trait loci (QTL) analysis procedures has recently allowed the first significant examination of the genetic control of QTs. Malt extract is a good example of a QT in barley. Heretofore, little has been known about the genetic control of malt extract. This study was initiated to elucidate the genetic characteristics of malt extract by analyzing the QTLs using a 'Steptoe' by 'Morex cross. QL analysis of data from the Steptoe x Morex F1-derived doubled haploid mapping population has revealed the locations of five malt extract QTLs on three of barley's seven chromosomes. Most of the chromosome regions involved also contain QTLs for other, related, malting quality traits including alpha-amylase activity, diastatic power, barley and malt beta-glucan contents, beta-glucanase activity and/or seed dormancy. The overlapping QTLs indicate either that the genes are linked, that pleiotropy is occurring, or both. Analyses also indicated that additive and G x E interactions affected the malt extract levels. Fine mapping of a critical region of chromosome 1 is in progress that should help elucidate the interactions responsible for these overlapping QTL effects. The location of specific genes affecting malt extract levels will facilitate more precise breeding, through the use of molecular marker assisted selection, for the improvement of this important barley trait.