1- Yasouj University
2- Shiraz University
2- Shiraz University
Abstract: (4 Views)
Extended Abstract
Introduction and objectives: Wheat is one of the most important crops in the world, having the third place in production, it is the first cereal in the world as the main source of calories and protein for humans. Increasing the yield of wheat is necessary due to the population increase. Drought stress is the most important factor in reducing plant production in many regions. The germination stage has a crucial role in properly establishing crops, and the genetic differences of this growth stage against stress provide a useful opportunity to select and understand the appropriate traits for stress tolerance. Considering the conditions of water defeciency and drought in Iran and the world, as well as the introduction of new varieties of wheat by research centers, investigation and identification of new and promising wheat varieties help plant breeders select varieties facing drought stress and It is of great importance.
Materials and methods: To study the effect of drought stress on the morphological characteristics of 15 bread wheat varieties (Alvand, Aflak, Pishgam, Pishtaz, Chamran, Zare, Sirwan, Saison, Shiroudi, Karim, Gasgagen, Gonbad, Morwarid, Mehan and Mehrgan) and 5 durum wheat varieties (Behrang, Shabarang, Yavarous, D-92-5 and D-91-16), a research was conducted in 2015-16 croping season in the laboratory of Darab Faculty of Agriculture and Natural Resources at the germination stage to identify drought tolerant cultivars. The experiment was conducted in a completely randomized design with three replications with two factors. Polyethylene glycol (PEG) 6000 with a concentration of 10% was used to apply drought stress
Results: The effect of genotype and stress interaction on germination percentage and rate, shootlet length, rootlet fresh weight, and shootlet fresh and dry weight was significant at 1% level. The highest percentage of germination in normal conditions belonged to the Karim cultivar and in stress conditions to the Aflak cultivar. The germination percentage in drought stress conditions showed a 4% decrease compared to normal conditions. The highest germination rate under normal conditions was related to the the Karim cultivar, which was not statistically different from the Behrang cultivar. Behrang cultivar had the highest germination rate under drought-stress conditions. Germination rate in stress conditions showed a 17% decrease compared to normal conditions and it was more sensitive to stress than germination percentage. The maximum shootlet length was related to the Zare variety under normal conditions and the Alvand variety under stress conditions. The shootlet length showed a 14% decrease in drought stress compared to normal conditions. Genotypes showed a significant difference at the 1% level in terms of rootlet and coleoptile length. Karim cultivar had the highest root length. Morvarid cultivar showed the highest coleoptile length, which was statistically not different from Alvand, Pishtaz, Chamran, Sirwan, Shiroudi, and Shabrang cultivars. The highest fresh weight of the rootlet was observed in the normal condition by the Karim variety (0.038 g) and in the stress condition by the Aflak variety (0.041 g). Karim, Mehan, and Aflak cultivars had the highest fresh weight of rootlet under stress conditions. In normal conditions, Shabrang and Pishgam cultivars had the highest shootlet fresh weight (0.072 g), and in stress conditions, the highest shootlet fresh weight was related to the D-91-16 variety (0.055 g). The rootlet fresh weight showed a 16% decrease in drought stress compared to normal conditions. Rootlet dry weight was not affected by the interaction of stress and genotype. The rootlet dry weight under stress conditions showed a 43% decrease compared to normal conditions and reached from 0.007 to 0.004 g. Karim cultivar had the highest rootlet dry weight (0.008 g). The effect of stress on shootlet dry weight was not significant. The highest rootlet dry weight belonged to the Mehrgan variety (0.0087 g) under normal conditions and the Mehan variety (0.0077 g) under stress conditions. Based on the group comparison between bread wheat and durum wheat under normal conditions, the highest rootlet length (10.27 cm), stem length (8.83 cm), root fresh weight (0.02 g), rootlet fresh weight (0.06 g) and shootlet dry weight (0.007 g) was related to bread wheat. Meanwhile, bread wheat and durum wheat did not show significant differences in terms of germination percentage, germination rate, coleoptile length, and rootlet dry weight. In the stress conditions, the highest germination percentage and germination rate with an average of 86.40 and 0.02 were related to durum wheat, and the highest rootlet length and dry weight were related to bread wheat with an average of 10.32 and 0.006 g, respectively.
Conclusion: Bread wheat genotypes showed a better situation under normal conditions and it can be said that they used the existing moisture condition well to improve the characteristics and are more suitable for irrigated cultivation. Under stress conditions, durum wheat showed the highest germination percentage and rate, which play an important role in the establishment of seedlings at the beginning of the growing season. Bread wheats had the highest rootlet length and dry weight, which increases the rootlet length and dry weight, is one of the important primary mechanisms in tolerant cultivars when faced with drought stress. Saison, Pishtaz, and Shiroudi cultivars of bread wheat and D-91-16 of durum wheat showed the lowest stress sensitivity based on germination percentage, which indicates the tolerance of these genotypes to drought stress. Alvand, Aflak, Pishtaz, Chamran, Saison, Shiroudi, Karim, Gasgagen, Gonbad, Morwarid, Mehan, Shabarang, Yavarous, and D-92-5 cultivars with high STI, high tolerance to drought stress and higher germination percentage in both stress and normal conditions compared to other cultivars and were among the desirable cultivars. Also, taking into account the germination percentage in Pishtaz cultivars, D-92-5 and D-91-16 showed the least sensitivity due to low SSI values, which indicates that these cultivars tolerate more drought stress, and therefore the Pishtaz cultivar from the bread wheat group, and the D-92-5 variety from the durum wheat group are known and introduced as the most tolerant varieties to drought stress.
Introduction and objectives: Wheat is one of the most important crops in the world, having the third place in production, it is the first cereal in the world as the main source of calories and protein for humans. Increasing the yield of wheat is necessary due to the population increase. Drought stress is the most important factor in reducing plant production in many regions. The germination stage has a crucial role in properly establishing crops, and the genetic differences of this growth stage against stress provide a useful opportunity to select and understand the appropriate traits for stress tolerance. Considering the conditions of water defeciency and drought in Iran and the world, as well as the introduction of new varieties of wheat by research centers, investigation and identification of new and promising wheat varieties help plant breeders select varieties facing drought stress and It is of great importance.
Materials and methods: To study the effect of drought stress on the morphological characteristics of 15 bread wheat varieties (Alvand, Aflak, Pishgam, Pishtaz, Chamran, Zare, Sirwan, Saison, Shiroudi, Karim, Gasgagen, Gonbad, Morwarid, Mehan and Mehrgan) and 5 durum wheat varieties (Behrang, Shabarang, Yavarous, D-92-5 and D-91-16), a research was conducted in 2015-16 croping season in the laboratory of Darab Faculty of Agriculture and Natural Resources at the germination stage to identify drought tolerant cultivars. The experiment was conducted in a completely randomized design with three replications with two factors. Polyethylene glycol (PEG) 6000 with a concentration of 10% was used to apply drought stress
Results: The effect of genotype and stress interaction on germination percentage and rate, shootlet length, rootlet fresh weight, and shootlet fresh and dry weight was significant at 1% level. The highest percentage of germination in normal conditions belonged to the Karim cultivar and in stress conditions to the Aflak cultivar. The germination percentage in drought stress conditions showed a 4% decrease compared to normal conditions. The highest germination rate under normal conditions was related to the the Karim cultivar, which was not statistically different from the Behrang cultivar. Behrang cultivar had the highest germination rate under drought-stress conditions. Germination rate in stress conditions showed a 17% decrease compared to normal conditions and it was more sensitive to stress than germination percentage. The maximum shootlet length was related to the Zare variety under normal conditions and the Alvand variety under stress conditions. The shootlet length showed a 14% decrease in drought stress compared to normal conditions. Genotypes showed a significant difference at the 1% level in terms of rootlet and coleoptile length. Karim cultivar had the highest root length. Morvarid cultivar showed the highest coleoptile length, which was statistically not different from Alvand, Pishtaz, Chamran, Sirwan, Shiroudi, and Shabrang cultivars. The highest fresh weight of the rootlet was observed in the normal condition by the Karim variety (0.038 g) and in the stress condition by the Aflak variety (0.041 g). Karim, Mehan, and Aflak cultivars had the highest fresh weight of rootlet under stress conditions. In normal conditions, Shabrang and Pishgam cultivars had the highest shootlet fresh weight (0.072 g), and in stress conditions, the highest shootlet fresh weight was related to the D-91-16 variety (0.055 g). The rootlet fresh weight showed a 16% decrease in drought stress compared to normal conditions. Rootlet dry weight was not affected by the interaction of stress and genotype. The rootlet dry weight under stress conditions showed a 43% decrease compared to normal conditions and reached from 0.007 to 0.004 g. Karim cultivar had the highest rootlet dry weight (0.008 g). The effect of stress on shootlet dry weight was not significant. The highest rootlet dry weight belonged to the Mehrgan variety (0.0087 g) under normal conditions and the Mehan variety (0.0077 g) under stress conditions. Based on the group comparison between bread wheat and durum wheat under normal conditions, the highest rootlet length (10.27 cm), stem length (8.83 cm), root fresh weight (0.02 g), rootlet fresh weight (0.06 g) and shootlet dry weight (0.007 g) was related to bread wheat. Meanwhile, bread wheat and durum wheat did not show significant differences in terms of germination percentage, germination rate, coleoptile length, and rootlet dry weight. In the stress conditions, the highest germination percentage and germination rate with an average of 86.40 and 0.02 were related to durum wheat, and the highest rootlet length and dry weight were related to bread wheat with an average of 10.32 and 0.006 g, respectively.
Conclusion: Bread wheat genotypes showed a better situation under normal conditions and it can be said that they used the existing moisture condition well to improve the characteristics and are more suitable for irrigated cultivation. Under stress conditions, durum wheat showed the highest germination percentage and rate, which play an important role in the establishment of seedlings at the beginning of the growing season. Bread wheats had the highest rootlet length and dry weight, which increases the rootlet length and dry weight, is one of the important primary mechanisms in tolerant cultivars when faced with drought stress. Saison, Pishtaz, and Shiroudi cultivars of bread wheat and D-91-16 of durum wheat showed the lowest stress sensitivity based on germination percentage, which indicates the tolerance of these genotypes to drought stress. Alvand, Aflak, Pishtaz, Chamran, Saison, Shiroudi, Karim, Gasgagen, Gonbad, Morwarid, Mehan, Shabarang, Yavarous, and D-92-5 cultivars with high STI, high tolerance to drought stress and higher germination percentage in both stress and normal conditions compared to other cultivars and were among the desirable cultivars. Also, taking into account the germination percentage in Pishtaz cultivars, D-92-5 and D-91-16 showed the least sensitivity due to low SSI values, which indicates that these cultivars tolerate more drought stress, and therefore the Pishtaz cultivar from the bread wheat group, and the D-92-5 variety from the durum wheat group are known and introduced as the most tolerant varieties to drought stress.
Keywords: Wheat, Drought stress, PEG, Drought tolerance, Stress susceptibility index, Cluster analysis
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