Enhancing yield of semidwarf barley

Semidwarf barley (Hordeum vulgare L.) lines and cultivars with the sdw gene have not fulfilled early expectations of increased grain yield. Accordingly, both breeding and molecular mapping experiments were undertaken to enhance and evaluate performance of lines with sdw. The objectives were to examine, in sdw semidwarf barley, the effect on grain yield of enhancing yield component traits-spike number, kernel number, and kernel weight-to confirm the reported allelic relationship between sdw and dense, to identify the chromosome location of sdw, and to determine the genetic relationship between sdw, height, and heading date. Eight tall barley lines having high yield-component phenotypes or high grain yield were crossed to 'Royal', an sdw semidwarf, to obtain semidwarf populations for study. Grain yield of semidwarf lines was not significantly increased by enhancing yield-component traits or by the use of high-yield parents. Allelism tests and gene mapping procedures were used to determine the relationship between sdw and dense and to map the sdw allele location. The sdw gene was allelic to dense and mapped to barley chromosome 3H in the same region as dense. The sdw allele reduced height by 10 to 20 cm and delayed maturity by approximate to 3 d. We hypothesize that the sdw allele itself, not linkage drag, is the basis for mediocre yield and late maturity of this short-stature germplasm. The information obtained encourages use of alternative short-stature sources.