NEAR-ISOGENIC ANALYSIS OF UNICULM AND CONVENTIONAL-TILLERING BARLEY LINES

The uniculm phenotype has been proposed as a component of a small grai n ideotype that maximizes crop productivity. Additionally, uniculm pla nts do not produce late-developing tillers that delay harvest and redu ce grain quality in short-season or northern areas of production. No c omprehensive studies that assessed the uniculm phenotype in barley (Ho rdeum vulgare L.) using near-isogenic lines were found in the literatu re. This study was conducted to compare the performance of uniculm and conventional-tillering near-isogenic barley lines that differed by th e presence of the uc(2) (uniculm) gene. Two pairs of near-isogenic lin es 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 li nes. However, maximum grain yield of uniculm lines was only 52% of tha t of conventional-tillering lines. At all seeding rates, spikes per sq uare meter and kernels per spike of uniculm lines were lower than conv entional-tillering lines, but kernel weight was higher. The lower grai n yield of uniculm lines was due primarily to reduced kernels per spik e at high seeding rates. Selection for grain yield or kernels per spik e at high seeding rates should be investigated as a possible means of increasing grain yield of uniculm lines.