To study general combining ability(GCA) and gene action for resistance to sunn pest(Eurygaster integriceps) six lines of bread wheat numbered 7214 ,6412,c-75-4,18,14,12 plus azadi variety werw crossed in a half-diallel system. Seven parents and twenty-one hybrids were evaluated in a randomized complete block design with 3 replication at Tehran University Research Station during the years 2005-2006. Analysis of variance indicated that among all of traits except for weight of sunn pest damaged kernel, difference existed at 1% level of significant. Results of combining ability analysis showed that in all traits, additive and non- additive variances in inheritance is important. Considering GCA for resistance to sunn pest line 7214 was the best and line 18 was the worst. Considering specific combining ability(SCA) for resistance to sunn pest damage with regard to all of traits the azadi×c-75-4 hybrid was the best and the 18×12 hybrid was the worst. Study of Hayman genetics parameters confirmed the results of Griffing GCA analysis indicating that in all traits additive and non- additive components are effective in inheritance except 50 kernel weight damaged, sunn pest seed damaged percent and height. But dominant variance is more important in these traits. For all traits except awn length exist over dominance, furthermore in all traits nonsymmetrical distribution of negative and positive effects and environment effect is also important.

Keywords: Diallel analysis, Sunn Pest, Griffing analysis, Hayman analysis.

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