SEEDING RATE AND GENOTYPE EFFECTS ON AGRONOMIC PERFORMANCE AND GRAIN PROTEIN CONTENT OF DURUM WHEAT ( Triticum turgidum   L. var. durum) IN SOUTH-EASTERN ETHIOPIA

The use of optimum seeding rate for the genotype may enhance productivity and grain protein content of durum wheat. Therefore, an experiment was conducted at two locations in south-eastern Ethiopia during the main cropping season of 2008 with the objective of elucidating the effects of seeding rate and genotype on agronomic performance and grain protein content of the crop. The experiment consisted of factorial arrangements of four improved durum wheat genotypes and five seeding rates, which were laid out as a randomized complete block design with three replicates. Seeding rates significantly influenced agronomic performances including number of fertile spikes m^-2, plant height, number of seeds spike^-1, and grain yield. Number of fertile spikes m^-2 was increased proportionally with the seeding rate and the highest number (382 spikes m^-2) was recorded in the highest seeding rate of 200 kg ha^-1. Inversely, the highest number of kernels spike^-1 (29.8) was at the seeding rate of 100 kg ha^-1. The highest grain yield (4341 kg ha^-1) was obtained in response to seeding rate of 175 kg ha^-1, which was in statistical parity with the yield obtained at the seeding rate of 150 kg ha^-1. However, grain protein content was not influenced by the seeding rates. There were significant (P ≤ 0.05) variations among the genotypes for all the agronomic traits measured. The largest number of fertile spikes m^-2 was recorded for the genotypes Oda (360 spikes m^-2) and Bakalcha (345 spikes m^-2). Genotype Illani produced the longest spike (6.9 cm). Oda and Illani produced the highest numbers of seeds spike^-1, 38.8 and 36.9, respectively. The number of fertile spikes m^-2, number of seeds spike^-2 and kernels weight significantly contributed grain yield. The genotypes had exhibited less variation for grain protein content. Except for grain yield and harvest index, seeding rate x genotype interaction had no significant effect on other agronomic traits. Highest grain yields of 4938 kg ha^-1 and 4774 kg ha^-1 were obtained from genotypes Ejersa and Bakalcha when sown at the seeding rate of 150 kg ha^-1 and 175 kg ha^-1, respectively. Grain protein response was significantly influenced by the interaction effect in which genotype Oda had the highest (12.9%) and lowest (10.5%) protein contents at the highest (200 kg ha^-1) and lowest (100 kg ha^-1) seeding rates, respectively.