Effectiveness of drought tolerance indices to identify tolerant genotypes in bread wheat ( Triticum aestivum L.)
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J. Crop Sci. Biotech. 2014 (December) 17 (4) : 255 ~ 266 DOI No. 10.1007/s12892-014-0080-7 RESEARCH ARTICLE
Effectiveness of Drought Tolerance Indices to Identify Tolerant Genotypes in Bread Wheat (Triticum aestivum L.) Mahmoud A. El-Rawy, Mohamed I. Hassan* Department of Genetics, Faculty of Agriculture, Assiut University, Assiut, Egypt Received : July 25, 2014 / Revised: September 9, 2014 / Accepted: September 12, 2014 Ⓒ Korean Society of Crop Science and Springer 2014
Abstract In order to assess efficiency of drought tolerance indices, 50 bread wheat genotypes were evaluated under three environments: normal (clay fertile soil, E1), 100% (E2), and 50% (E3) field water capacity in sandy calcareous soil. A total of 14 drought tolerance indices including grain yield/plant, grain yield/spike, 1000-kernel weight, spike length, no. of tillers, plant height, flowering time, stomata frequency, stomata width, stomata length, drought susceptibility index (DSI), stress tolerance index (STI), yield stability index (YSI), and harmonic mean (HM) were estimated. A moderate to high broad-sense heritability was obtained for 1000-kernel weight (0.47), spike length (0.38), plant height (0.54), flowering time (0.73), stomata frequency (0.59), and stomata length (0.54). Grain yield/plant was strongly positively correlated with grain yield/spike, no. of tillers, plant height, flowering time, stomata length, STI, YSI, and HM, while negatively correlated with stomata frequency and DSI in E2 and E3, respectively. Thus, highly heritable traits strongly correlated with grain yield under stress conditions especially stomata frequency and length could be used as reliable indices for selecting high-yielding genotypes tolerant to drought stress. Cluster analysis based on morpho-physiological traits suggested the group 3 genotypes in E2 as the most tolerant genotypes to be used for developing improved varieties. Key words : bread wheat, cluster analysis, correlation, drought tolerance, selection indices
Introduction Drought stress is the most limiting factor affecting growth and productivity of crop plants including wheat. Drought due to insufficient soil water supply frequently occur concurrently with high temperature at the end of wheat-growing season in the regions of the world with a Mediterranean climate like Egypt. Of specific importance to crop plants is not whether they survive stress, but whether they show good yields under stress conditions (Bhargava and Sawant 2013). Rosielle and Hamblin (1981) defined stress tolerance as the differences in yield between the stress and non-stress environments. Generally, it is agreed that drought tolerance from a breeding viewpoint is a complex trait that shows a high level of genotype × environment (Cooper et al. 2006). Furthermore, plant responses to drought are also influenced by the time, intensity, duration, and frequency of the stress as well as by diverse plant–soil–atmosphere interactions (Saint Pierre et al. 2012). However, for studies on adaptation of crop plants to complex Mohamed I. Ha
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