Evaluation of Yield, Dry Matter Accumulation and Leaf Area Index in Wheat Genotypes as Affected by Terminal Drought Stress
AbstractGrain yield of wheat (Triticum aestivum L.) under Mediterranean conditions is frequently limited by both high temperature and drought during grain growth. In this region, most rain falls during autumn and winter and water deficit emerges in the spring, resulting in a moderate stress for rainfed wheat around anthesis, which increases in severity throughout grain filling. Hence, selection of genotypes with high grain yield is the principal aim of wheat production in this region. In order to evaluation of yield and dry matter accumulation in wheat genotypes as affected by terminal drought stress, a factorial experiment based on randomized complete block design was conducted in Research Farm Islamic Azad University, Ardabil branch in 2009. Factors were: terminal drought stress by changing in planting date at three levels (12 October, 1 November and 21 November) with wheat (Triticu aestivum L.) genotypes at four levels (‘Azar-2’, ‘Sardari’, ‘Frankia’ and ‘Trakia’). The results showed that various levels of terminal drought stress affected yield, dry matter accumulation and leaf area index in wheat genotypes. Means comparisons showed that maximum grain yield (183.18 gr/m2) was obtained at the first of planting date or the least duration of confronting with thermal drought stress in ‘Azar-2’ genotype and minimum of it was obtained in the third planting date with ‘Trakia’ genotype due to the highest duration of confronting with thermal drought stress. Investigation of variances trend of dry matter accumulation indicated that in all of treatment compounds, it increased slowly until 190-200 days after sowing and then increased rapidly till 270-280 days after sowing. From 280 days after sowing till harvest time, it decreased due to increasing aging of leaves and decreasing of leaf area index. In the other hand, wheat genotypes had difference response to dry matter accumulation in confronting with thermal drought stress. Decrease in duration of terminal drought stress also significantly increased the leaf area index and the maximum of it was observed by the plots that were applied in the first planting date with ‘Azar-2’ genotype. In all of treatment compounds, LAI increased slowly until 190-200 days after sowing and then decreased slowly till 240-250 days after sowing. From 240-250 days after sowing till harvest time, it decreased rapidly due to hasten leaf senescence in confronting with terminal drought stress. Thus, it can be suggested that in order to increasing of grain yield, dry matter accumulation and leaf area index should be applied ‘Azar-2’ genotype with the first planting date(12 October ) in conditions of Ardabil Plain in Iran.
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