-

In 1989 six Iranian cultivars were crossed in a fuil-diallel crossing system. In the following year parental lines and the Fl-hybrids were sown in a randomized block design and six quantitative characters were evalueted. Because three reciprocal crosses failed, results were analyzed by means of the haif-diallel method. The results showed significant differences between genotypes and a high general and specific combining abilities for the investigated characters of parental cultivars and their Fl-hybrids..
Calculations and graphic interpretations of the results of diallel crosses revealed that characters such as tillers per plant, plant height and the length to breadth ratio of brown rice were mostly controlled by additive gene action and through partial dominance. These characters have a high heritability and therefor selection for these characters may be succeed.
Genetic control of characters such as earliness, length of panicles, and percentage of empty grains per panicles is exerted by over-dominance. Because of a high
amount of non-additive gene action and, thus, low heritability of these characters, the chance of successful selection for those characters is not very high.