Genetics of certain traits of bread wheat (Triticum aestivum L.)

A four-parent complete diallel cross of wheat (Triticum aestivum L.), cultivars viz, Nuri, Sonalika, Pak-70 and Pavon was analyzed for plant height, spikes per plant, spike length, spikelets per spike, number of grains per spike, seed index and grain yield per plant. The material was sown in randomized complete block design (RCBD) with three replications. Ten plants from each genotype per replication wore randomly selected for recording the data. The mean square for the character grains per spikelet was non- significant. Mean squares for the remaining Character were significantly at 1% level of probability. Gene action for all the traits studied varied. Plant height showed over-dominance type of gene action and Sonalika had maximum, dominant genes, while Nuri had most of the recessive alleles for this trait. Number of spikes per plant showed additive type of gene action, the variety, Nuri had dominant genes and Pak-70 had the recessive genes. Spike length indicated additive type of gene action, while Pavon had the dominant genes and Pak-70 had most of the recessive genes. Number of spikelets per spike expressed Additive (type of gene action with partial dominance, Sonalika had the most dominant genes, while Nuri had most of the recessive genes. Number of grains per spike indicated over- dominance type of gene action, cultivar Sonalika had the maximum dominant germs, and Pak-70 had most of the recessive genes. Seed index revealed additive type of gene action with partial dominance, Pak-70 had maximum dominant genes and Pavon had the recessive genes. Grain yield per plant displayed the additive type of gene act- ion with partial dominance and Sonalika had the maximum dominant genes being closer to the origin, while Pavon possessed the recessive genes being away from the origin. Two traits expressed dominance type of gene action. Two gene group/two genes controlled, plant height, spike length and number of grains per spike, moreover one gene group/one (trite controlled number of spikes per plant, number of spikelets per spikes, seed index and grain yield per plant. The ratio of proportion of positive and negative genes in the parents for the traits plant height, number of spikelets per spike, were equal distributed, while the characters number of spikes per plant and grain yield per plant indicated as asymmetrical distribution as well as the traits spike length, number of grains per spike and seed index indicate were not equal distribution. The ratio proportion of dominant and recessive genes or parent for the traits plant height, number of spikes per plant, spike length, number of grain per spike, seed index and grain yield per plant indicate excess of dominant genes while for the trait number of spikelets per spike expressed excess of recessive genes. Non-significant correlation (r) value showed that plant height and seed index was controlled by both dominant and recessive genes. However, negative significant correlation (r) value indicated that spike length was governed by dominant genes, while positive significant correlation (r) value expressed that number of spikes per plant, number of spikelets per spike, number of grains per spike and grain yield per plant were controlled by recessive genes. Whereas, low narrow sense heritability were recorded for the traits plant height, number of spikes per plant and number of grains per spike, while moderate narrow sense ability were estimated for the characters number of spikelets per spike and grain yield per plant, moreover, high narrow sense heritability were recorded for the spike length and seed index traits.