Abstract

Twenty eight hybrid combinations of eight selected inbred lines ((including 3 lines sensitive (A679, K3651/1 and K3640/5), 2 lines medium (K47/2-2-1-21-2-1-1-1 and K19) and 3 lines tolerance to heat stress (K18, K166A and K166B)) with different response to heat stress were evaluated in 2008 for grain yield and some related traits in a randomized complete block design arranged into three replications in Shoushtar City (a sub-tropical region in Khuzestan Province of Iran). Hybrids were planted at two planting dates, 6th of July (coinciding heat stress with pollination time and grain filling period) and 27th of July (normal planting). Diallel analysis was done using Griffing’s method 4 and model II. As a result, grain yield in heat stress condition and 1000 grain weight in both conditions showed high general combining ability to specific combining ability ratio, indicating the effects of additive contribution. But grain yield in normal condition, grain number per ear, grain row number per ear, grain number per ear row and hektolitr weight in both conditions showed low GCA/SCA, indicating contribution of non-additive effects. General combining ability of all traits was non-significant in parents except for grain row number per ear. K18×K166B of the highest yield, positive and combining significantly in both conditions for grain yield was enjoyed.

Key words: Maize, heat stress, additive and non-additive effects, combining ability, hybrid.