M. Rahimi - Department of Agronomy and Plant Breeding, College of Agricultural Sciences, University of Guilan, P. O. Box: ۴۱۶۳۵-۱۳۱۴, Rasht, Islamic Republic of Iran.
B. Rabiei - Department of Agronomy and Plant Breeding, College of Agricultural Sciences, University of Guilan, P. O. Box: ۴۱۶۳۵-۱۳۱۴, Rasht, Islamic Republic of Iran.
H. Samizadeh - Department of Agronomy and Plant Breeding, College of Agricultural Sciences, University of Guilan, P. O. Box: ۴۱۶۳۵-۱۳۱۴, Rasht, Islamic Republic of Iran.
A. Kafi Ghasemi - Department of Agronomy and Plant Breeding, College of Agricultural Sciences, University of Guilan, P. O. Box: ۴۱۶۳۵-۱۳۱۴, Rasht, Islamic Republic of Iran.

Quantitative valuations of observed heterosis for ۱۱ traits of ۱۵ F۱ hybrids generated by half diallel crosses of six diverse rice cultivars (Domsefid, Hashemi and Binam, three Iranian local cultivars; Dorfak, Kadous and IR۳۰, three improved cultivars), were made in this study. Fifteen F۱ hybrids and their parents were evaluated in a randomized complete block design with three replications at the Research Farm of the University of Guilan at Rasht, (Iran) in ۲۰۰۶. The studied traits were growth period, reproductive period, flag leaf area, plant height, panicle length, number of panicles per plant, number of grains per panicle, ۱۰۰۰-grain weight, grain yield, brown grain length and brown grain width. The significance of specific combining ability (SCA) and general combining ability (GCA) for all studied traits revealed that both additive and non-additive gene effects contributed to the inheritance of the traits. Assessment of standard heterosis based on check variety Dorfak showed that there was significant heterosis for all the traits studied in the ۱۵ hybrids. For grain yield, the Dorfak×Domsefid cross had the highest heterosis. This hybrid had good heterosis values for many traits such as growth period, reproductive period and ۱۰۰۰-grain weight and was recommended as the most promising combination for developing high yielding hybrid rice varieties.

Rice, General combining ability, Heterosis, Specific combining ability