Evaluating of gene actions controlling grain cooking quality related traits in rice varieties

To estimate the gene action and heritability of traits related to cooking quality in rice varieties, F₂ generations derived from diallel crosses of six rice varieties including Hassani, Shahpasand, Kadous, Vandana, Hashemi and IR36, together with their parents were assessed in a randomized complete block design with three replications in research field of Faculty of Agricultural Sciences, University of Guilan, in 2012. Result of diallel analysis based on the second method of Gardner and Eberhart showed that variety and heterosis effects were significant at 1% probability level for all studied traits indicating additive and dominance variances, respectively. Average heterosis was significant for gelatinization temperature showing significant differences between average parents and hybrids, but was not significant for amylase content and gel consistency. In contrast, specific heterosis was significant for all studied traits. Result of diallel analysis on the basis of third method of Gardner and Eberhart demonstrated that differences among parents and among crosses were significant for all measured traits indicating general and specific combining ability for varieties, while the effect of parents versus crosses (heterosis effect) was not significant for amylase content and gel consistency that confirmed the results of the second method of Gardner and Eberhart. Estimation of Baker ratio showed the higher non-additive than additive effects for amylase content, approximately equal proportion of the additive and non-additive effects for gel consistency and the higher additive than non-additive effects for gelatinization temperature. The graphical analysis of Hayman method showed that all measured traits were affected by partial dominance effects and relatively high narrow-sense heritability indicated higher proportion of additive gene effects for controlling the studied traits. Totally, the results of this research showed that to improve grain cooking quality in the studied population, can firstly be used the additive gene effects via selecting the higher quality genotypes and then the dominance gene effects is utilized by hybridization of the superior genotypes. Furthermore, IR36, Kadous and Shahpasand varieties and Hashemi×Shahpasand, Kadous×Hassani, Hassani×Shahpasand and Kadous×IR36 Crosses had the suitable values for grain cooking quality related traits and are recommended to improve these traits.