| چکیده انگلیسی مقاله |
Introduction: Plants are constantly exposed to biotic and abiotic stresses. Among these stresses, water-deficit stress is considered one of the most important adverse factors for the growth and performance of plants and a serious threat to the sustainable production of crops under changing climate conditions (Lambers et al., 2008). Human food security heavily depends on cereals, especially wheat. However, the production of these crops is affected by water-deficit stress.
Materials and Methods: The current experiment was conducted at Tabriz University, Iran in 2021-22 growing season. Plant materials included 25 winter wheat cultivars and promising lines, which were evaluated under two irrigation conditions (30 mm evaporation from the class A pan (non stress) and 100 mm evaporation from the class A pan (drought stress). The experiment was conducted as a split-plot design in a randomized complete block design five replications. Two levels of irrigation were assigned to main plots and 25 winter wheat genotypes were randomized in sub-plots. Root traits such as root fresh and dry weight, root length, root area, root volume, root diameter, root density, grain yield per plant and biochemical attributes such as proline and malondialdehyde contents, for 16 selected genotypes were measured in two replications.
Results: Analysis of variance showed that there was significant differences among the wheat wheat cultivars and promising lines for all studied traits. There were significant difference between two irrigation conditions for all traits, except root density. On the other hand, the interaction effect of stress and genotype was significant for all traits. Analysis of variance for biochemical attributes for 16 selected wheat genotypes, in two replications, showed that there was significant difference among the studied genotypes for proline and malondialdehyde contents. There was significant difference between two irrigation levels. The interaction of stress and genotype was significant for proline and malondialdehyde contents. Correlation analysis between grain yield and root area (r = 0.467*), root diameter (r = 0.559**), root fresh weight (r = 0.478*), root length (r = 0.495*), root volume (r = 0.397*), malondialdehyde content (r = 0.649**) and proline content (r = 0.507*) were positive and significant under drought stress conditions. The cluster analysis of 25 wheat genotypes based on all studied traits, grouped them in two clusters for two irrigation conditions. Also, cluster analysis for proline and malondialdehyde contents, in two irrigation conditions, grouped 16 selected genotypes in two clusters. According to the results of this experiment, under stress conditions, cv. Sardari, cv. Azar2, cv. Takab, cv. Ivan, cv. Rasad, cv. Homa, DARI-12 promising line, cv. Owhadi, DARI-11 promising line, cv. Parav, cv. Sadra, and DARI-13, DARI-16 and DARI-19 promising lines can be considered for better root traits such as root length, root area, root volume, root diameter, root density, root fresh and dry weight, a higher mean and high performance. Also, cv. Saeen, cv. Kamal, cv. Takab, DARI-19 promising line for having higher proline content. Cv. Azar2, cv. Ivan, DARI-16 and DARI-14 promising lines, cv. Sadra, cv. Hashtrood, cv. Rijav, cv. Parav, cv. Varan, DARI-12 promising line, cv. Homa, cv. Sardari had the lowest malondialdehyde content.
Conclusion: The results of this experiment showed that wheat genotypes under drought stress conditions, responded by decreasing or increasing of root traits to improve grain yield. These responses prevented the reduction of grain yield under drought stress conditions. Tolerant cultivars and promising lines had optimal grain yield under drought stress conditions. Grain yield had positive and significant correlation with root area, root diameter, root fresh weight, root length, root volume, proline cntent, and malondialdehyde content. Cultivars and promising lines with higher root length, root volume, root weight, root diameter, root area, proline and malondialdehyde contents showed higher tolerant to drought stress conditions. The results of cluster analysis of morphological root traits of 25 winter wheat cultivars and promising lines under two irrigation conditions, showed that cv. Sardari, cv. Azar2, cv. Takab, cv. Ivan, cv. Rasad, cv. Homa, DARI-12 promising line, cv. Owhadi, DARI-11 promising line, cv. Parav, cv. Sadra, and DARI-13, DARI-16 and DARI-19 lines had better morphological root traits with mean root area of 129.5 cm2, root density of 0.32 g.cm-3, root diameter of 0.14 mm, root dry weight of 2.36 g, root fresh weight of 8.48 g, root length of 75.5 cm, root volume of 12.6 cm3 and mean of grain yield of 3.05 g.plant-1. Also, cv. Saeen, cv. Kamal, cv. Takab, and DARI-19 line, had the highest mean of proline content (0.31 µmol g-1 FW) and cv. Azar2, cv. Ivan, DARI-16 and DARI-14, cv. Sadra, cv. Hashtrood, cv. Rijav, cv. Parav, cv. Varan, DARI-12 line, cv. Homa, cv. Sardari had the lowest mean of malondialdehyde content (0.18 µmol.g-1 FW). In general, based on the results of this experiment, cv. Sardari, cv. Azar2, cv. Takab, cv. Ivan, cv. Rasad, cv. Homa, DARI-12 line, cv. Owhadi, DARI-11 line, cv. Parav, cv. Sadra, and DARI-13, DARI-16 and DARI-19 promising lines that had better morphological and biochemical traits and grain yield were identified as superior drought tolerant cultivars and promising lines.
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