SEEDING RATE EFFECTS ON LOW-TILLERING SPRING WHEATS IN A SEMIARID ENVIRONMENT
To determine if increased seeding rates would alter relative yields of traditional and low-tillering genotypes, a high-tillering (Neepawa), a low-tillering (Siete Cerros), and an oligoculm (M1417) spring wheat (Triticum aestivum L.) genotype were seeded in replicated field trials at two locations in 1984 and 1985. A four-replication split-plot design, with genotypes assigned to main plots and seeding rates (40, 80 160, 320 and 640 seeds m−2) to subplots, was used for each experiment. Grain yield and its components were measured on individual plots or on main stems of five plants in each plot. All three genotypes expressed maximum yield at the same seeding rate (640 seeds m−2 in 1984 and 320 seeds m−2 in 1985) in the semiarid conditions of these experiments. Despite diverse tillering habits, the relative yields of these three genotypes could not be altered by changing seeding rates. On average, Siete Cerros (low-tillering) yielded 15% more than Neepawa and 17% more than M1417. Neepawa had lower grain yields than M1417 at all seeding rates in 1984, but higher grain yields in 1985. A similar change in relative performance of these two genotypes was observed for harvest index of the main stem but not for main stem grain yield kernels spike −1 on the main stem or kernel weight.Key words: Wheat (spring), oligoculm, yield components, genotype-environmental interaction.