1- Department of Agriculture and Plant Breeding, Faculty of Agriculture, Yasouj University, Yasouj, Iran
2- Department of Agroecology, Darab Faculty of Agriculture and Natural Resources, Shiraz University, Darab, Iran
2- Department of Agroecology, Darab Faculty of Agriculture and Natural Resources, Shiraz University, Darab, Iran
Abstract: (184 Views)
Extended Abstract
Background: Wheat ranks third in production and is the world's first grain as the main source of calories and protein for humans. Increasing wheat grain yield is essential due to the increasing population. Drought stress is considered the most important factor in reducing plant production in many regions. The germination stage plays a decisive role in the proper establishment of crop plants, and genetic differences at this stage under stress conditions provide a useful opportunity for selecting and understanding appropriate traits for stress tolerance. Considering the conditions of water deficit and drought in Iran and the world, as well as the introduction of new varieties of bread and durum wheat by research and scientific centers, the study and evaluation of new and promising wheat varieties are of great importance and help plant breeders in selecting varieties to face drought stress.
Methods: To investigate the effect of drought stress on the morphological characteristics of 15 bread wheat cultivars (Alvand, Aflak, Pishgam, Pishtaz, Chamran, Zare, Sirvan, Saison, Shiroudi, Karim, Gaskogen, Gonbad, Morwarid, Mehan, and Mehrgan) and five durum wheat cultivars (Behrang, Shebrang, Yavarous, D-92-5, and D-91-16) and to identify drought-tolerant cultivars, a study was conducted at the germination stage in the laboratory of the Faculty of Agriculture and Natural Resources, Darab, Iran, in the 2016-2017 crop year. The experiment was conducted as a factorial experiment in a completely randomized design with three replications. Polyethylene glycol (PEG) 6000 at a concentration of 10% was used to apply drought stress.
Results: The effect of the stress and genotype interaction was highly significant on the germination percentage and rate, shootlet length, fresh weight of rootlet, and fresh and dry weights of the shootlet. The highest germination percentage belonged to the Karim and Aflak cultivars in normal and stress conditions, respectively. The average germination percentage in drought stress conditions showed a 4% decrease compared to normal conditions. The highest germination rate was shown by the Karim and Behrang cultivars in normal conditions and by the Behrang cultivar in drought stress conditions. The germination rate in stress conditions showed an average decrease of 17% compared to normal, and was more sensitive to the germination percentage. Shootlet length in drought stress conditions showed a 14% decrease compared to normal conditions, and the highest values were recorded for the Zare and Alvand cultivars in normal and stress conditions, respectively. The genotypes showed different lengths of rootlet and coleoptile. The highest average lengths of rootlet and coleoptile were shown by the Karim and Morwarid cultivars, respectively. The cultivars Alvand, Pishtaz, Chamran, Sirvan, Shiroudi, and Shabrang were not different from the Morwarid cultivar in coleoptile length. The highest fresh rootlet weight was shown by the Karim cultivar (0.038 g) in normal conditions and by the Aflak (0.041 g), Karim, and Mehan cultivars in stress conditions. The cultivars Shabrang and Pishgam (0.072 g) in normal conditions, and the cultivar D-91-16 (0.055 g) in stress conditions presented the highest fresh shootlet weight. The fresh shootlet weight decreased by 16% in drought stress compared to normal conditions. The average dry rootlet weight of the cultivars (0.004 g) decreased by 43% under stress conditions compared to normal conditions (0.007 g). The Karim cultivar showed the highest dry rootlet weight (0.008 g). The highest shootlet dry weights in normal and stress conditions belonged to the cultivars Mehrgan (0.0087 g) and Mehan (0.0077 g), respectively. Bread wheat had the highest rootlet length, shootlet length, rootlet fresh weight, shootlet fresh weight, and shootlet dry weight under normal conditions. Under stress conditions, the highest germination percentage and rate were measured for durum wheats, and the highest rootlet length and dry weight were found for bread wheats. Pishtaz, D-92-5, and D-91-16 cultivars showed the lowest stress susceptibility index (SSI) based on the germination percentage. Higher heritability was observed for the germination rate, and shootlet fresh and dry weight under normal conditions compared to stress conditions. However, germination percentage, shootlet length, and rootlet fresh weight showed higher heritability under stress conditions.
Conclusion: Bread wheat genotypes showed better performance under normal conditions, and it may be claimed that they utilized the available moisture conditions well to improve characteristics and growth conditions. Under stress conditions, durum wheats 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 wheat had the highest rootlet length and dry weight, which are important mechanisms for dealing with drought stress in tolerant plants. The cultivars Alvand, Aflak, Pishtaz, Chamran, Saison, Shiroudi, Karim, Gaskogen, Gonbad, Morwarid, Mehan, Shabrang, Yavarous, and D-92-5 gained higher germination percentages under both stress and non-stress conditions than the other cultivars and were among the desirable cultivars. Based on heritability, it can be stated that the germination percentage and rate, shootlet dry weight, and coleoptile length in both normal and drought stress conditions, shootlet fresh weight in normal conditions, and shootlet length and rootlet fresh weight in drought stress conditions can be selected for in the early generations of segregation. The cultivars in different clusters showed similar and close germination percentage, rootlet length and dry weight, rootlet and shootlet fresh weight, or shootlet dry weight. Under drought stress conditions, the cultivars Alvand, Pishgam, Pishtaz, Zare, Sirvan, Morwarid, Mehan, Shabrang, and Yavarous from both bread and durum wheat groups showed high or moderate overall drought resistance and were statistically similar in terms of root and shoot fresh weight. The results of cluster analysis showed that cultivars might react differently under different growth conditions, once again confirming the need to examine cultivars under different environmental conditions for breeding. A breeding program can be designed considering the presence of cultivars in specific groups. Cultivars that are in the same group are more similar, and if desired, similar cultivars can be used to enhance the desired traits, or cultivars in different groups can be used in hybridization to create genetic diversity. Finally, based on the overall results, the cultivars Aflak, Karim Alvand, Pishgam, Pishtaz, Zare, Sirvan, Morwarid, Mehan, Shabrang, and Yavarous were identified as resistant cultivars at the germination stage and are recommended for drought stress conditions.
Background: Wheat ranks third in production and is the world's first grain as the main source of calories and protein for humans. Increasing wheat grain yield is essential due to the increasing population. Drought stress is considered the most important factor in reducing plant production in many regions. The germination stage plays a decisive role in the proper establishment of crop plants, and genetic differences at this stage under stress conditions provide a useful opportunity for selecting and understanding appropriate traits for stress tolerance. Considering the conditions of water deficit and drought in Iran and the world, as well as the introduction of new varieties of bread and durum wheat by research and scientific centers, the study and evaluation of new and promising wheat varieties are of great importance and help plant breeders in selecting varieties to face drought stress.
Methods: To investigate the effect of drought stress on the morphological characteristics of 15 bread wheat cultivars (Alvand, Aflak, Pishgam, Pishtaz, Chamran, Zare, Sirvan, Saison, Shiroudi, Karim, Gaskogen, Gonbad, Morwarid, Mehan, and Mehrgan) and five durum wheat cultivars (Behrang, Shebrang, Yavarous, D-92-5, and D-91-16) and to identify drought-tolerant cultivars, a study was conducted at the germination stage in the laboratory of the Faculty of Agriculture and Natural Resources, Darab, Iran, in the 2016-2017 crop year. The experiment was conducted as a factorial experiment in a completely randomized design with three replications. Polyethylene glycol (PEG) 6000 at a concentration of 10% was used to apply drought stress.
Results: The effect of the stress and genotype interaction was highly significant on the germination percentage and rate, shootlet length, fresh weight of rootlet, and fresh and dry weights of the shootlet. The highest germination percentage belonged to the Karim and Aflak cultivars in normal and stress conditions, respectively. The average germination percentage in drought stress conditions showed a 4% decrease compared to normal conditions. The highest germination rate was shown by the Karim and Behrang cultivars in normal conditions and by the Behrang cultivar in drought stress conditions. The germination rate in stress conditions showed an average decrease of 17% compared to normal, and was more sensitive to the germination percentage. Shootlet length in drought stress conditions showed a 14% decrease compared to normal conditions, and the highest values were recorded for the Zare and Alvand cultivars in normal and stress conditions, respectively. The genotypes showed different lengths of rootlet and coleoptile. The highest average lengths of rootlet and coleoptile were shown by the Karim and Morwarid cultivars, respectively. The cultivars Alvand, Pishtaz, Chamran, Sirvan, Shiroudi, and Shabrang were not different from the Morwarid cultivar in coleoptile length. The highest fresh rootlet weight was shown by the Karim cultivar (0.038 g) in normal conditions and by the Aflak (0.041 g), Karim, and Mehan cultivars in stress conditions. The cultivars Shabrang and Pishgam (0.072 g) in normal conditions, and the cultivar D-91-16 (0.055 g) in stress conditions presented the highest fresh shootlet weight. The fresh shootlet weight decreased by 16% in drought stress compared to normal conditions. The average dry rootlet weight of the cultivars (0.004 g) decreased by 43% under stress conditions compared to normal conditions (0.007 g). The Karim cultivar showed the highest dry rootlet weight (0.008 g). The highest shootlet dry weights in normal and stress conditions belonged to the cultivars Mehrgan (0.0087 g) and Mehan (0.0077 g), respectively. Bread wheat had the highest rootlet length, shootlet length, rootlet fresh weight, shootlet fresh weight, and shootlet dry weight under normal conditions. Under stress conditions, the highest germination percentage and rate were measured for durum wheats, and the highest rootlet length and dry weight were found for bread wheats. Pishtaz, D-92-5, and D-91-16 cultivars showed the lowest stress susceptibility index (SSI) based on the germination percentage. Higher heritability was observed for the germination rate, and shootlet fresh and dry weight under normal conditions compared to stress conditions. However, germination percentage, shootlet length, and rootlet fresh weight showed higher heritability under stress conditions.
Conclusion: Bread wheat genotypes showed better performance under normal conditions, and it may be claimed that they utilized the available moisture conditions well to improve characteristics and growth conditions. Under stress conditions, durum wheats 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 wheat had the highest rootlet length and dry weight, which are important mechanisms for dealing with drought stress in tolerant plants. The cultivars Alvand, Aflak, Pishtaz, Chamran, Saison, Shiroudi, Karim, Gaskogen, Gonbad, Morwarid, Mehan, Shabrang, Yavarous, and D-92-5 gained higher germination percentages under both stress and non-stress conditions than the other cultivars and were among the desirable cultivars. Based on heritability, it can be stated that the germination percentage and rate, shootlet dry weight, and coleoptile length in both normal and drought stress conditions, shootlet fresh weight in normal conditions, and shootlet length and rootlet fresh weight in drought stress conditions can be selected for in the early generations of segregation. The cultivars in different clusters showed similar and close germination percentage, rootlet length and dry weight, rootlet and shootlet fresh weight, or shootlet dry weight. Under drought stress conditions, the cultivars Alvand, Pishgam, Pishtaz, Zare, Sirvan, Morwarid, Mehan, Shabrang, and Yavarous from both bread and durum wheat groups showed high or moderate overall drought resistance and were statistically similar in terms of root and shoot fresh weight. The results of cluster analysis showed that cultivars might react differently under different growth conditions, once again confirming the need to examine cultivars under different environmental conditions for breeding. A breeding program can be designed considering the presence of cultivars in specific groups. Cultivars that are in the same group are more similar, and if desired, similar cultivars can be used to enhance the desired traits, or cultivars in different groups can be used in hybridization to create genetic diversity. Finally, based on the overall results, the cultivars Aflak, Karim Alvand, Pishgam, Pishtaz, Zare, Sirvan, Morwarid, Mehan, Shabrang, and Yavarous were identified as resistant cultivars at the germination stage and are recommended for drought stress conditions.
Keywords: Cluster analysis, Drought stress, Drought tolerance, PEG, Stress susceptibility index, Wheat
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