Fine structure mapping of the barley chromosome-1 centromere region containing malting-quality QTLs |
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| Authors: | F Han S E Ullrich A Kleinhofs B L Jones P M Hayes D M Wesenberg |
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| Institution: | (1) Department of Crop and Soil Sciences, Washington State University, Pullman, WA 99164, USA Fax: +1509-335-8674 E-mail: hanfeng@mail.wsu.edu., US;(2) Cereal Crops Research Unit, USDA-ARS, 501 N. Walnut St., Madison, WI 53705, USA, US;(3) Department of Crop and Soil Science, Oregon State University, Corvallis, OR 97331, USA, US;(4) National Small Grains Germplasm Research Facility, P.O. Box 307, Aberdeen, ID 83210, USA, US |
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| Abstract: | Current techniques for quantitative trait locus (QTLs) analyses provide only approximate locations of QTLs on chromosomes.
Further resolution of identified QTL regions is often required for detailed characterization. An important region containing
malting-quality QTLs on barley (Hordeum vulgare L.) chromosome 1 was identified by previous QTL analyses in a Steptoe×Morex cross. This region contains two putative adjacent
overlapping QTLs, each of which has effects on malt-extract percentage, α-amylase activity, diastatic power, and malt β-glucan
content. All favorable alleles for these traits are attributed to Morex. The objective of the present study was fine structure
mapping of this complex QTL region to elucidate whether these two putative overlapping QTLs are really one QTL. Another question
was whether the apparently overlapping QTLs are due to the pleiotropic effects of a single gene, or the independent effects
of several genes. A high-resolution map in the target region was developed which spans approximately 27 cM. Molecular-marker-assisted
backcrossing was employed to create isogenic lines with a Steptoe background differing only in the region containing the QTLs
of interest. A total of 32 different recombinants were identified, of which eight most-informative isogenic lines plus one
reconstructed Steptoe control were selected for field testing. The additive effects on malt-extract percentage, α-amylase
activity, diastatic power, and malt β-glucan content from eight isogenic lines were calculated based on malting data from
three locations. By comparing the significant additive effects among isogenic lines carrying different Morex fragments, two
QTLs each for malt extract and for α-amylase, and two to three for diastatic power were identified in certain environments
and resolved into 1–8-cM genome fragments. There was a significant QTL×environment interaction for diastatic power, and there
are indications that epistatic interactions for malt β-glucan content occur between the QTLs on chromosome 1 and QTLs on other
chromosomes.
Received : 4 June 1997 / Accepted : 19 June 1997 |
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| Keywords: | Fine mapping Additive effects Marker assisted backcrossing Isogenic lines |
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