effect of moisture stress on agronomic and morphological characteristics of recombinant inbred lines in wheat (triticum aestivum l.)

introduction drought stress as the most important abiotic stress plays an important role in yield reduction of crops worldwide. considering the extends and problems caused by the moisture stress, agronomic and breeding strategies in reducing yield loss are essential. in this regard, the identification and selection of effective characteristics of wheat under drought stress in increasing yield, is essential. determining the most important morphological characteristics affecting wheat yield under stress, in order to achieve the criteria for selection to improve the performance of this plant always has been important in breeding programs. due to the variation in drought tolerance in wheat genotypes, it is necessary for efficient water usage in each region, cultivars with higher performance and better compatibility under lower irrigation requirement should be determined for efficient water use particularly in regions with scarce water resources. improvement of a complex trait such as yield possessing low heritability, requires indirect selection using simpler traits viz morph-physiological traits. materials and methods this study was conducted to evaluate the effects of water stress on the agronomic and morphological traits of 169 recombinant inbred lines (rils) in wheat (triticum aestivum l.), using two separate lattice design (drought and control) at research farm of isfahan university of technology in 2011-2012. recombinant inbred lines of wheat were obtained from the international center for wheat and maize improvement (cimmyt) in mexico. the recombinant inbred lines used in this study were derived from a cross between two seri m82 and babax parents after being selfed for 8 generations (f9). seeds of each line were planted in a three meter row with a row distance of 30 cm. irrigation, fertilization and control weeds in the experimental was conducted and to provide plant requirement n, based on soil analysis, urea fertilizer at the rate of 100 kg per hectare in two stages of growth were added to the ground in early spring. two moisture regimes of 70 and 130 mm evaporation from evaporation pan class a (16% and 20% moisture by weight of soil, respectively) were employed, and soil moisture was measured during two irrigation treatments. in both experiments normal irrigation was conducted till middle of jointing stage, and were irrigated afterward based on class of the evaporation pan. results and discussion drought stress significantly reduced days to heading, days to pollination, days to maturity, spike length, plant height, the number of spikes per m2, the number of grains per spike, grain weight in the spike, 1000-grain weight, biological yield, grain yield and harvest index. results of analysis of variance revealed significant differences among lines for all studied traits under normal conditions with the exception of number of grains per spike, grain weight in the spike, spike length, days to pollination and days to maturity. under moisture stress conditions, the rils significantly varied between the studied traits with the exception of number of grains per spike, 1000-grain weight and spike length. the correlation coefficients in the normal conditions showed that all traits had a positively correlated with grain yield with the exception of spike length and days to pollination. under the moisture stress conditions the grain yield was correlated with all traits positively. the results of the factor analysis in both normal and stress moisture conditions showed that the measured traits have appeared either in a hidden factors which explained 67.09% and 84.26% of the total variation of the yield, respectively. using three dimensional profiles, lines 4, 27 and 40 as the superior genotypes were introduced in terms of three factors. based on the fernandez’s drought tolerance index lines 1 and 69 were identified as the most drought tolerant and the most drought sensitive ones, respectively. the results of stepwise regression on the grain yield under normal and moisture-stress conditions revealed that the number of spikes per m2 and the grain weight in spike contributed 95% of the grain yield variations in both environmental conditions. conclusions the results showed significant effects of drought on crop yield, morphological and phenological (days to maturity, days to pollination and days to heading), and only on the number of grains per plant, grain weight and spike were not significant. therefore, in spite of inheritance variation in the studied lines supported by their effects from the environmental conditions. also, considering the high heritability of these traits, it was concluded that these traits were less affected by the environment. under normal compared to water stress conditions, the narrow-sense heritability of harvest index was lower. in normal conditions, the highest narrow-sense heritability belonged to the number of spike per m² (77%), but under water stress conditions, belonged to the grain yield (84%). according to the results, it can be concluded that the number of spikes per m2 and the grain weight in spike have been the two most important components of gain yield under both normal and drought stress conditions. moreover, the superior drought tolerance lines have the potential to improve the grain yield in both environmental conditions in the breeding programs.