Abstract: (12 Views)
Extended Abstract
Introduction and Objectives:
Avoiding the occurrence of environmental stresses and their damages on crop production, as well as the increasing consequences of climate change, have prompted plant breeders to continuously help seed producers in dealing with these problems with genetic manipulating. In this research, a community of wheat cultivars were grown under irrigated and rainfed conditions to determine their response to water deficit stress and the amount of genetic diversity in these cultivars was measured in terms of stress tolerance, agronomic traits and ISSR markers.
Materials and Methods:
The experiment was carried out in the agricultural year of 2018 and 2019 at Gorgan University of Agricultural Sciences and Natural Resources. The studied population included 34 varieties of bread wheat from tolerant and resistant to drought germplasm, which are grown in various regions of Iran. In the field, the cultivars comparison experiment was carried out in two conditions of irrigated cultivation (no stress) and rainfed (water stress) in the form of a randomized complete block design with 3 replications. During the growing season, important agronomic and morphological traits such as flag leaf length and width, spike length, plant height, number of plants per plot, number of spikes, number of tillers, number of seeds per spike, seed weight and seed yield were measured. Fernandez's drought tolerance index was calculated for all cultivars and analyzed along with other characteristics. In the laboratory, the markers obtained from the ISSR primers for the DNA of each cultivar were evaluated and their scores were analyzed. Necessary statistical analyzes such as analysis of variance, comparison of means and cluster analysis were performed in SAS software and analyzes related to polymorphic marker bands and Nei and Shannon gene indices were performed in POPGEN and NTSYS software.
Results:
In addition to the existence of genetic diversity in the population, observing the significant difference of the cultivars for all the measured characteristics, which obtained from the analysis of variance was a confirmation of the good choice of the genotypes in terms of type, agronomic characteristics, adaptibility and their origin that correctly realized the study of variation and grouping of genotypes which were the main objective of the study. The highest seed yield in irrigated conditions belonged to cultivars Karkheh, Behrang and Arta and in rainfed conditions belonged to s-87-18, Baz and Zagros. Also, cultivars Karon, Maron, Ohari, s-87-18 and Zagros showed relatively similar performance under both irrigated and rainfed conditions.
According to Fernandez index cultivars Karkheh, S-87-18, Bahar, Chamran, Arta, Pasteur, Baz, Wibil, Behrang, Nik-Nejad, Hirmand have the highest and Maron, Kavir, Fang-Chen, Zagros, Gonbad have the lowest tolerance to water stress. These values can be directly used as a criterion for selecting high-yielding cultivars under water stress conditions. Cluster analysis of cultivars based on agronomic traits in both stress and non-stress conditions produced three distinct cluster. In the water stress conditions, cluster 1 included 2 cultivars (s-87-18 and Gohar) and cluster 2 consisted of 3 cultivars (Maron, Kavir and Fang Chen). 29 other cultivars of this study were placed in cluster 3. According to the value of drought tolerance index, it can be stated that cluster 1 included drought tolerant cultivars, cluster 2 included cultivars sensitive to drought stress and cluster 3 were moderate cultivars. The composition of cultivars in three clusters was changed over stress and no-stress conditions, which was mainly caused by the effect of the drought stress on morphological charactrestics of the plants, which can be interpreted as the reaction of these cultivars in the facing to drought. ISSR primers produced a total of 128 bands with an average polymorphism percentage of 93.27% for 11 used primers. In other words, each primer produced an average of 11.69 bands and the average PIC index in the primers used was 0.28. The Nei and Shannon index values for the studied population were calculated as 0.26 and 0.41, respectively. Cluster analysis based on ISSR data showed that except for Maron, other cultivars were separated into three distinguished clusters.
Conclusion:
In general, the results showed that there is a significant genetic variation in the studied population, which makes it possible to select cultivars with higher tolerance to water stress or cultivation in rainfed conditions. Fortunately, since the studied cultivars are improved and are being cultivated, their direct use or gene transfer for projects to increase wheat yield in water stress conditions will be easier and faster.
Introduction and Objectives:
Avoiding the occurrence of environmental stresses and their damages on crop production, as well as the increasing consequences of climate change, have prompted plant breeders to continuously help seed producers in dealing with these problems with genetic manipulating. In this research, a community of wheat cultivars were grown under irrigated and rainfed conditions to determine their response to water deficit stress and the amount of genetic diversity in these cultivars was measured in terms of stress tolerance, agronomic traits and ISSR markers.
Materials and Methods:
The experiment was carried out in the agricultural year of 2018 and 2019 at Gorgan University of Agricultural Sciences and Natural Resources. The studied population included 34 varieties of bread wheat from tolerant and resistant to drought germplasm, which are grown in various regions of Iran. In the field, the cultivars comparison experiment was carried out in two conditions of irrigated cultivation (no stress) and rainfed (water stress) in the form of a randomized complete block design with 3 replications. During the growing season, important agronomic and morphological traits such as flag leaf length and width, spike length, plant height, number of plants per plot, number of spikes, number of tillers, number of seeds per spike, seed weight and seed yield were measured. Fernandez's drought tolerance index was calculated for all cultivars and analyzed along with other characteristics. In the laboratory, the markers obtained from the ISSR primers for the DNA of each cultivar were evaluated and their scores were analyzed. Necessary statistical analyzes such as analysis of variance, comparison of means and cluster analysis were performed in SAS software and analyzes related to polymorphic marker bands and Nei and Shannon gene indices were performed in POPGEN and NTSYS software.
Results:
In addition to the existence of genetic diversity in the population, observing the significant difference of the cultivars for all the measured characteristics, which obtained from the analysis of variance was a confirmation of the good choice of the genotypes in terms of type, agronomic characteristics, adaptibility and their origin that correctly realized the study of variation and grouping of genotypes which were the main objective of the study. The highest seed yield in irrigated conditions belonged to cultivars Karkheh, Behrang and Arta and in rainfed conditions belonged to s-87-18, Baz and Zagros. Also, cultivars Karon, Maron, Ohari, s-87-18 and Zagros showed relatively similar performance under both irrigated and rainfed conditions.
According to Fernandez index cultivars Karkheh, S-87-18, Bahar, Chamran, Arta, Pasteur, Baz, Wibil, Behrang, Nik-Nejad, Hirmand have the highest and Maron, Kavir, Fang-Chen, Zagros, Gonbad have the lowest tolerance to water stress. These values can be directly used as a criterion for selecting high-yielding cultivars under water stress conditions. Cluster analysis of cultivars based on agronomic traits in both stress and non-stress conditions produced three distinct cluster. In the water stress conditions, cluster 1 included 2 cultivars (s-87-18 and Gohar) and cluster 2 consisted of 3 cultivars (Maron, Kavir and Fang Chen). 29 other cultivars of this study were placed in cluster 3. According to the value of drought tolerance index, it can be stated that cluster 1 included drought tolerant cultivars, cluster 2 included cultivars sensitive to drought stress and cluster 3 were moderate cultivars. The composition of cultivars in three clusters was changed over stress and no-stress conditions, which was mainly caused by the effect of the drought stress on morphological charactrestics of the plants, which can be interpreted as the reaction of these cultivars in the facing to drought. ISSR primers produced a total of 128 bands with an average polymorphism percentage of 93.27% for 11 used primers. In other words, each primer produced an average of 11.69 bands and the average PIC index in the primers used was 0.28. The Nei and Shannon index values for the studied population were calculated as 0.26 and 0.41, respectively. Cluster analysis based on ISSR data showed that except for Maron, other cultivars were separated into three distinguished clusters.
Conclusion:
In general, the results showed that there is a significant genetic variation in the studied population, which makes it possible to select cultivars with higher tolerance to water stress or cultivation in rainfed conditions. Fortunately, since the studied cultivars are improved and are being cultivated, their direct use or gene transfer for projects to increase wheat yield in water stress conditions will be easier and faster.
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