Submitted to: Plant Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/31/1997
Publication Date: N/A
Interpretive Summary: When trying to breed improved barley varieties, it is often hard or expensive to detect the genes that, when present, result in barleys having improved malting quality. To get around this, we have now mapped many of the genes of barley so that, theoretically, if we select barley plants that contain certain easy-to-detect characteristics, they will also contain the genes that cause them to have better malting quality. The malting quality genes are thus tagged with easily detectable genes. This paper reports an experiment carried out to determine whether, in practice, this method works. Two particular areas of two chromosomes were thought to be exceptionally important in determining the malting quality of the barley, and both were tagged with easily detected areas at their ends. Crosses of two barleys having varying malting quality were made and the resulting progeny were separated into good and poor malting quality lines by four different methods, some using tagging, some not. For selecting barleys improved by genes located at one of the areas, the tagging method was superior to the classical, more expensive methods. At the other it was not; probably because the genes located in this area did not affect malting quality in this particular cross. This work shows that the tagging method does work, allowing breeders to relatively easily and cheaply select out those new barleys that have improved malting quality.
Technical Abstract: Selection for malting quality in breeding programs by micromalting and micromashing is time-consuming and expensive. More efficient and feasible approaches for identifying good malting quality genotypes would be highly desirable. Using molecular markers, it is now possible to map and tag the loci that affect malting quality. This study was conducted to assess the effectiveness of molecular marker assisted selection for malting quality traits. Two major quantitative trait loci (QTL) regions in six-row barley chromosomes 1 (QTL1) and 4 (QTL2) have been previously identified. These control malt extract percentages, alpha-amylase activity, diastatic power, and malt beta-glucan contents. The flanking markers, Brz and Amy2, and WG622 and BCD402B, for these two QTL regions were used to conduct marker-assisted selections. Four alternative selection strategies; phenotypic selection, genotypic selection, tandem genotypic and phenotypic selection, and combined phenotypic and genotypic selection, were compared for trait selection in a population of 92 doubled haploid lines derived from "Steptoe" x "Morex" crosses. Marker assisted selection for QTL1 (tandem genotypic and phenotypic selection, and combined phenotypic and genotypic selection) was more effective than phenotypic selection, but for QTL2 was not as effective as phenotypic selection due to a lack of QTL2 effects in the selection population. The effectiveness of tandem genotypic and phenotypic selection makes marker assisted selection practical for traits which are difficult or expensive to measure.