عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Background and Objectives
Wheat (Triticum aestivum L.) is one of the most widely cultivated crops in rainfed areas of Iran where drought is the main limiting factor of production. Yield in drought-prone environments may be considered to be affected by three factors including yield potential, appropriate phenology and drought tolerance. Despite the positive correlation between grain yield in drought stress and normal conditions indirect selection based on yield potential, mean yield under non-stress conditions may not give the best results for selection of drought tolerant genotypes. Grain yield is strongly affected with genotype by environmental interaction. On the other hand, this interaction is relatively small for secondary traits. Hence, evaluation of genetic control of yield and yield related traits was the main objective of the present study.
Materials and methods
In order to estimate genetic parameters of yield and its related traits in bread wheat, a half diallel mating design was generated using nine (9) cultivars including Mahdavi, Azar2, Roushan, Ghods, Kavir, Excalibur, Shiraz, Kalhaydari, Shiraz and Shahpasand, and their F2 progenies. For this purpose, genotypes were planted in a Randomized Complete Block (RCB) design under normal and drought stress conditions. Plant height (cm), awn length (cm), biomass (t/ha), grain number per spike, fertile tiller number, days to flowering (days), grain filling period and grain yield (t/ha) were evaluated in this research. Hayman and Jinksdeiallel method was used to estimate genetic parameters including additive and dominant variance. In addition, variances of general and specific combining ability were estimated using Griffingmethod.
Analysis of variance showed significant genotypic variation for all traits. Diallel analysis indicated that both additive and non-additive effects were valuable for genetic control of most characters. Awn length and days to flowering had the highest narrow sense heritability. Narrow sense heritability of grain yield under normal conditions was significantly higher than drought stress conditions. Plant height and awn length in both conditions and grain number per spike under drought stress condition were identified as the most appropriate traits in wheat breeding programs. These traits had high narrow sense heritability and low non-additive effects.
Genetic analysis of evaluated traits showed that non-additive effects played a significant role in genetic control of the most characters. Based on these results, bulk and single seed descent are recommended methods for breeding in this population even though, awn length and days to flowering showed high narrow sense heritability.