JWSS - Journal of Water and Soil Science

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The Genetic basis of grain yield and related characteristics were studied by a generation mean analysis in five crosses of winter wheat (Triticum aestivum L.). “Roshan”, “Mahdavi”, “Inia”, “Atila” and “Goscoyin” cultivars along with their F₁, F₂, BC₁ and BC₂ populations were evaluated by a split-plot design with crosses as the whole plot in a randomized complete block design with two replications and generations were applied as the subplots. Analysis of variance revealed significant differences among generations for studied characteristics including the grain yield per plant, the number of spikelet per plant, the number of spikelet per spike and grain weight per spike. For the majority of traits and crosses, F/DH^1/2 was less than one, indicating that the sign and magnitude of gene actions were different. Estimates of broadsense and narrow sense heritabilities were low for the grain yield per plant compared with other traits, rating from 28.5% to 58.6% and 24% to 48,5% for the five crosses, respectively. Genetic components of generation means were calculated by fitting different models and choosing the best model indicated that the impact of additive, dominance and epistasis genetic components in controlling the traits depend on the cross and the trait under study.

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In order to estimate the number and inheritance of controlling genes for grain yield and some of the related traits in barley, Afzal and Radical varieties along with their F₁, F₂ and F₃ generations were planted in a randomized complete block design with three replications. Head weight, head length, number of heads, number of spikelets, awn length, hundred grain weight, grains per head, straw yield per head , harvest index and grain yield in different generations were recorded. Analysis of variance indicated that mean squares of generations were statistically significant for all the traits. Then, generation mean analysis was performed for all the traits. Based on the results, additive and dominance effects played roles in controlling awn length. For the other traits besides the aforesaid effects, epistasis effect was also significant. Also, results indicated that dominance variance had the most important role in controlling the inheritance for traits. The average broad sense heritability for all the traits was estimated between %69 - %89. The number of genes for all traits was estimated to be between one and six.

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In order to study gene action in rice for traits related to quality (gelatinization temperature, gel consistency and amylose content), four varieties of rice (Sang-e-Tarrom, Gerdeh, IRRI2 and IR229) were investigated. Ten different generations including P1, P2, F1, RF1, BC1, RBC1, BC2, RBC2, F2 and RF2 were evaluated using generation mean analysis. In generation mean analysis, one of non-allelic interaction components, [i], [j]1, [j]2, [l]1, [l]2, [l] was significant indicating the genetic model of these characters were described by additive-dominance model with non-allelic gene interaction (except for gelatinization temperature trait in Sang-Tarrom × Gerdeh cross). The cross IRRI2×IR229 showed duplicate epistasis for gel consistency trait. Cytoplasmic effects and interactions between cytoplasmic and nuclear effects in two crosses were significant for amylose content and gel consistency traits. The estimation of narrow and broad-sense heritability for two crosses were 0.77 to 0.99 and 0.05 to 0.93, respectively. The predominantly additive nature of the genetic variability was further revealed by the variance components. Component D was detected significant in all the crosses. The covariance component and , however, showed indirectly that dominance contributed significantly to variability at the variance level. Therefore, according to the obtained results, selection can be effectively done in later segregation generations for gel consistency and amylose content and in early generation for traits.