A study was conducted on genetics of some important phonological traits (heading date, plant height and panicle length) in rice. Five lines were crossed with 2 testers in line × tester fashion to produce 10 F1 hybrids. Results showed that GCA effect was only significant for heading date and SCA effect was significant for heading date and plant height. Four parents including three lines (Neda-A/IR36, IR36 and Pouya) and one tester (Usen) showed highest negative GCA for heading date and were identified as better general combiners for early maturation. Lines Pouya and IR42 showed highest negative GCA for plant height, indicating that these lines were good general combiners for reducing plant height. Line Neda-A/IR36 showed highest significant GCA for panicle length, indicating that this line was a good general combiner for panicle length. Combinations Usen/IR42 and IR68897/IR42 showed significant SCA in opposite directions for plant height (10.7 and -10.7 cm, respectively), indicating that hybridization can be a choice for improving hybrids with shorter height. Highest general heritability (h2 b) was obtained for heading date (97.5%), indicating slight effects of environment on the trait. Highest specific heritability (h2 n) was obtained for heading date (73.3%), indicating that additive effects control the trait. In contrast, minimum h2 n was obtained for plant height and panicle length, indicating that non-additive effects play important roll in genetic control of these traits. Therefore, it seems that improving the lines with early maturation will be promising via selection in segregating populations, while hybridization must be preferred for plant height and panicle length.
