Diallel Analysis for Heterosis Study and Estimation of Genetic Parameters for some Morphological Traits in Rice

Seven rice varieties (Hassani, Deilmani, Sepidruod, Shahpasand, Saleh, Neda and IRFAON215) and their complete diallel progenies were grown in a randomized complete block design with three replications in the growing seasons of 2006 and 2007 at the Rice Research Institute of Iran (RRII) in Rasht. Genetic components, the mode of inheritance and heterosis of various physiological traits were studied by using seven-parent diallel mating design including reciprocals. Results revealed that both additive and non-additive gene effects were important for inheritance of days to flowering, plant height and panicle exsertion with preponderance of additive gene effects. Inheritance of harvest index was controlled only by additive effects. While, inheritance of grain yield, panicle length and flag leaf area were governed by non-additive gene effects. ‘F’ value, showing an excess of dominant alleles in the parents, was significant only for grain yield. The average degree of dominance (H1/D) 0.5 was within the range of partial dominance for days to flowering, plant height, panicle exsertion and harvest index. At least two major groups of genes controlled the inheritance of plant height, and panicle length and flag leaf area, four major groups the inheritance of harvest index and one group the inheritance the other traits. The highest value of relative heterosis was observed for panicle exsertion and grain yield. Wr-Vr graphic analysis indicated that increase of flag leaf area, plant height, panicle exsertion and panicle length was under the control of dominance alleles, but harvest index was increased by recessive alleles. Due to the importance of non-additive components for grain yield, panicle length and flag leaf area, biparental mating and/or reciprocal recurrent selection could be used for genetic improvement of these characters. Predominance of additive effects for remainder of the traits demonstrated that breeding methods based on selection may be advantageous in improving of these traits in rice using the studied materials.