| چکیده انگلیسی مقاله |
Heritability and gene actions of some important quantitative agronomic traits were studied in the progenies of a cross between a drought tolerant and a susceptible barley lines in normal irrigation and terminal drought stress conditions. A cross was made between two genotypes EC 84-12 and 1-BC-80455 susceptible and tolerant to drought, respectively. Parents as well as F1, F2, BC1 and BC2 generations were evaluated under field conditions in two separate experiments using randomized complete block design (RCBD) with three replications. These experiments were carried out in the research field station, Seed and Plant Improvement Institute, Karaj, Iran in 2005-2006 and 2006-2007 cropping cycles. In normal irrigation and terminal drought stress conditions, irrigation was applied until physiological maturity and anthesis stages, respectively. Plant height, spike length, awn length, grain yield plant-1, 1000 grain weight (TGW), harvest index (HI), number of days to heading, number of days to physiological maturity were measured and recorded. Analysis of variances in both environments indicated that significant differences were found between generations for all traits therefore, generation mean analysis could be performed. Results revealed that under both normal irrigation and terminal drought stress conditions, all traits, except harvest index, were controlled by additive, dominance and epistatic gene effects. For traits as grain yield plant-1, TGW, HI, the contribution of dominance gene effects under terminal drought stress conditions was higher, considering the dominance/additive ratio, as compared to normal irrigation conditions. Comparison of gene actions in both normal irrigation and terminal drought stress conditions indicated that the contribution of dominance genes effects has been increased as compared to the additive gene effect for grain yield plant-1, and harvest index, number of days to physiological maturity, and decreased for plant height, spike length, awn length. In general, for traits showed high ratio of additive to dominance gene effect, selection could be effective in early generation, however for traits with high dominance to additive gene effects selection should be made in later generations till desirable genes are fixed. The broad and narrow sense of heritabilities for the traits under normal irrigation ranged between 0.43 to 0.69 and 0.31 to 0.43, respectively. In terminal drought stress conditions, heritabities ranged between 0.41 to 0.81 and 0.36 to 0.45, respectively. The maximum number of genes for the traits under normal irrigation and terminal drought stress conditions was estimated 1.51 and 4.32 genes, respectively. |