Mapping quantitative trait loci for long coleoptile in Chinese wheat landrace wangshuibai
Wheat (Triticum aestivum L.) cultivars with long coleoptiles can be sown deeply for better seedling establishment in drought environments. A population of 139 recombinant inbred lines (RILs) from a cross between a long-coleoptile Chinese landrace, Wangshuibai, and short-coleoptile U.S. wheat cultivar, Wheaton, were characterized for coleoptile length and plant height. Heritabilities for coleoptile length were high (h2 > 0.82). Interval mapping identified six significant quantitative trait loci (QTL) on 1B, 3D, 4DS, 4DL, 5AS, and 5B for coleoptile length; four of them, on 3D, 4DS, 4DL, and 5AS, showed pleiotropic effects on plant height. One major QTL for long coleoptile was mapped on the locus Rht-D1 (Rht2) for reduced height (Rht) on chromosome 4DS and explained up to 65% of phenotypic variation for coleoptile length. Another major QTL was located on 4DL and explained up to 33% of phenotypic variation for coleoptile length. Standard height allele Rht-D1a from Wangshuibai appeared to have an epistatic effect on the 4DL QTL for long coleoptile. Other QTL showed only a minor effect. Although Rht-D1a explained a major portion of genetic variation for long coleoptile in Wangshuibai, a combination of Rht-D1a in Wangshuibai with gibberellic acid (GA)–sensitive Rht genes for reduced wheat height from other sources should be able to select long coleoptiles, semidwarf cultivars in wheat breeding programs for which long coleoptile is a breeding objective.