Near-isogenic analysis of uniculm and conventional-tillering barley lines

The uniculm phenotype has been proposed as a component of a small grain ideotype that maximizes crop productivity. Additionally, uniculm plants do not produce late-developing tillers that delay harvest and reduce grain quality in short-season or northern areas of production. No comprehensive studies that assessed the uniculm phenotype in barley (Hordeum vulgare L.) using near-isogenic lines were found in the literature. This study was conducted to compare the performance of uniculm and conventional-tillering near-isogenic barley lines that differed by the presence of the uc(2) (uniculm) gene. Two pairs of near-isogenic lines were evaluated at seeding rates of 50, 140, 230, and 320 kernels m(-2) and row spacings of 15 and 30 cm, for 3 yr at Palmer, AK. Uniculm lines matured an average of 6 d earlier than conventional-tillering lines. However, maximum grain yield of uniculm lines was only 52% of that of conventional-tillering lines. At all seeding rates, spikes per square meter and kernels per spike of uniculm lines were lower than conventional-tillering lines, but kernel weight was higher. The lower grain yield of uniculm lines was due primarily to reduced kernels per spike at high seeding rates. Selection for grain yield or kernels per spike at high seeding rates should be investigated as a possible means of increasing grain yield of uniculm lines.