Mapping quantitative trait loci for starch granule traits in barley

Starch accumulates in barley (Hordeum vulgare L.) endosperm in large (type A) and small (type B) granules. The sizes, shapes and relative proportions of A and B granules may affect the quality of barley malt for brewing. The objective of this study was to use genetic markers to map quantitative trai t loci (QTL) affecting starch granule traits in a cross between a malting b arley cultivar, Morex, and a feed barley cultivar, Steptoe. Data on starch granule dimensions were obtained using digital image analysis. With simple interval mapping, a region of chromosome 2 (2H) was found to contain QTL af fecting the overall mean granule volume, the proportion of A granules, the mean volume of A granules, the mean maximum diameter of A granules and the mean F-shape of B granules. This region also affected days to heading and p lant height, but contained no QTL for grain or malt quality traits. With co mposite interval mapping, QTL affecting starch granule traits were detected in two additional regions, one on chromosome 4 (4H) affecting the mean F-s hape of B granules and one on chromosome 7 (5H) affecting the mean maximum diameter of A granules. (C) 1999 Academic Press.