genetic analysis of appearance and cooking quality traits in different rice cultivars

to assess heritability, gene action and combining ability of rice varieties for characteristics related to grain appearance and cooking quality, the progenies derived from direct and reverse crosses of the 6×6 complete diallel together with their parents included hashemi, hassani, shahpasand, kadous, vandana and ir36 were grown in a randomized complete block design with three replications in the research field of the rice research institute of iran (rrii), rasht, iran, during 2011 cropping season. the studied traits were included amylase content, gelatinization temperature, grain length, width and thickness and grain length to width ratio (grain shape). results showed that mean squares of both general and specific combining ability for all studied traits except grain width were significant that indicate both additive and non-additive gene effects have an important role in the expression of the traits, but the role of the additive gene effects was more important than the non-additive gene effects. the results of graphical analysis of hayman showed that the share of additive variance (d) of grain length, width and thickness, grain shape and gelatinization temperature was greater than dominance variance (h1). genetic analysis of these traits represents the role of partial dominance gene action in controlling the traits that indicate the potential of selection for these traits. the role of partial to complete dominance gene actions were observed in the controlling amylase content, so using selection and hybrid seed production can be considered by reformers to improve this trait. thus, to improve the grain appearance and cooking quality in the studied population, selection method can be firstly used to increase favorable genes and finally hybridization method is performed to use the dominance gene effects. comparing different methods of griffing in evaluation of combining ability of varieties showed that using parents in diallel analysis probably cause a bias in the results of combining abilities. so using third and in the absence of maternal effects fourth method of griffing’s, in addition to fewer treatments and expenses, are applied and better methods in assessment of combining ability.