YIELD COMPONENT COMPENSATION IN UNICULM BARLEY LINES

Asynchronous spike maturation in barley (Hordeum vulgare L.) grown at northern latitudes, caused by late-developing tillers, frequently resu lts in harvest delay, reduced grain quality, and increased drying cost s. The uniculm trait has been suggested to promote uniform spike matur ation and increased grain yield; however, the literature contains no i nformation on the field performance of genetic uniculm lines. The purp ose of this study was to assess the performance and yield component co mpensation of uniculm barley lines having the uc2 gene. Five spring ba rley lines were grown at seeding rates of 35, 90, 145, and 200 kg ha-1 at Palmer and Fairbanks, AK in both 1991 and 1992. Higher seeding rat es resulted in shorter plants, earlier maturity, increased spikes per square meter, and reductions in kernels per spike and kernel weight. R esults from path analysis demonstrated that spikes per square meter wa s the primary determinant of grain yield, followed by kernels per spik e, with kernel weight of only minor importance. Increasing spikes per square meter caused relatively large reductions in kernels per spike a nd kernel weight, while increasing kernels per spike caused only minor reductions in kernel weight. Maximum grain yield was attained at the 200 kg ha-1 seeding rate in Fairbanks and at the 90 or 145 kg ha-1 see ding rate at Palmer. The relatively low grain yield of uniculm lines a ppears to be due to a low number of kernels per spike at higher spike densities.