Reza Darvishzadeh *1 
, Mona Bordbar1, Hamid Hatami Maleki2, Maryam Tahmasbali1, Amir Fayaz Moghaddam1
, Mona Bordbar1, Hamid Hatami Maleki2, Maryam Tahmasbali1, Amir Fayaz Moghaddam1
1- Department of Plant Production and Genetics, Faculty of Agriculture, Urmia University, Urmia, Iran
2- Department of Plant Production and Genetics, Faculty of Agriculture, University of Maragheh, Maragheh, Iran
2- Department of Plant Production and Genetics, Faculty of Agriculture, University of Maragheh, Maragheh, Iran
Abstract: (152 Views)
Extended Abstract
Background: Tobacco (Nicotiana tabacum L.) with 2n = 4x = 48 chromosomes is one of the most important industrial and economic plants in many countries of the world, which is mainly cultivated for harvesting and collecting its leaves. Due to its polygenic nature, the performance of tobacco is significantly affected by both abiotic and biotic stresses, including the weed Orobanche. In this context, the response of varieties to the environment varies depending on the genotype of the cultivar, which is referred to as the genotype × environment interaction. By studying the genotype × environment interaction and analyzing stability, it is possible to select genotypes that have satisfactory performance in various environmental conditions. Although there are many reports on the use of stability methods in assessing the response of plants to the environment, there are no reports on the stability of dry leaf yield of tobacco across environments contaminated with weeds. This project aims to evaluate the response of existing oriental tobacco genotypes in the country's tobacco germplasm in two environments: with and without Orobanche weeds, to identify and select compatible and stable genotypes in the studied environments.
Methods: In this experiment, 92 oriental and semi oriental type tobacco genotypes were evaluated in terms of tolerance to Orobanche stress based on a randomized complete block design with three replications. The tobacco genotypes were prepared from the genetic and biological resources bank of the Urmia Tobacco Research Center and the Tirtash Tobacco Research Institute (Mazandaran). For cultivation, 10-liter clay pots were selected and filled with soil prepared from an alfalfa field, and the pots were arranged according to the experimental design plan in an open area space in the Urmia Tobacco Research Center. Alfalfa is not the host of Orobanche, and its long-term establishment in the field (usually 6 years) does not permit Orobanche seed dispersion in the soil; therefore, the soil should be almost free of Orobanche seeds. In the experiment with Orobanche infection, the soil of the pots, before being filled, was mixed with 0.06 g of Orobanche cernua seeds (containing approximately 12,000 seeds), which were collected from the field of Urmia Tobacco Research Center one year before starting the experiment. In the north-west regions and especially in West Azerbaijan, this type of Orobanche is predominant on the tobacco and is seen more often in the fields. The seedlings of each tobacco genotype were prepared in the bed, and when the tobacco seedlings reached a height of 12 cm, they were transferred to the pots. All agricultural operations, such as transplanting, irrigation, adding soil at the base of the plant, and protecting against pests and diseases during the tobacco growing period, were carried out according to the existing standards for oriental tobacco. The leaves of tobacco genotypes were harvested at the time of industrial ripening (about 45-50 days after transplanting) three times, dried in the sun, and weighed using a digital scale with an accuracy of 0.001 g. The univariate parameters of stability were calculated after individual and combined analyses of variance.
Results: The results of the analysis of variance showed a significant difference among tobacco genotypes for all the studied traits. Moreover, the genotype × environment interaction was significant for all traits, indicating different responses of tobacco genotypes under Orobanche-stressed and non-stressed conditions. Mean comparisons showed that the Orobanche stress reduced the averages of all morphological traits. Stability analysis using methods based on variance and regression analyses revealed that genotypes 45, 33, and 78 had the highest coefficient of variation, indicating the lowest level of stability. Among these, genotype 45 had a mean value higher than the overall mean. Furthermore, genotypes 75, 53, and 41 were identified as stable genotypes due to possessing the lowest stability variance. According to the Plastid and Peterson method (θi), genotypes 75, 55, 53, and 41 showed the lowest θi values. Among these, genotype 53 demonstrated a mean performance higher than the overall average.
Conclusion: By evaluating the stability of genetic materials, stability indices can be highly beneficial for the optimal and efficient selection of parental genotypes to develop high-yielding and stress-tolerant cultivars. Based on different stability methods, genotype 53 is introduced as a stable genotype with optimal performance.
Background: Tobacco (Nicotiana tabacum L.) with 2n = 4x = 48 chromosomes is one of the most important industrial and economic plants in many countries of the world, which is mainly cultivated for harvesting and collecting its leaves. Due to its polygenic nature, the performance of tobacco is significantly affected by both abiotic and biotic stresses, including the weed Orobanche. In this context, the response of varieties to the environment varies depending on the genotype of the cultivar, which is referred to as the genotype × environment interaction. By studying the genotype × environment interaction and analyzing stability, it is possible to select genotypes that have satisfactory performance in various environmental conditions. Although there are many reports on the use of stability methods in assessing the response of plants to the environment, there are no reports on the stability of dry leaf yield of tobacco across environments contaminated with weeds. This project aims to evaluate the response of existing oriental tobacco genotypes in the country's tobacco germplasm in two environments: with and without Orobanche weeds, to identify and select compatible and stable genotypes in the studied environments.
Methods: In this experiment, 92 oriental and semi oriental type tobacco genotypes were evaluated in terms of tolerance to Orobanche stress based on a randomized complete block design with three replications. The tobacco genotypes were prepared from the genetic and biological resources bank of the Urmia Tobacco Research Center and the Tirtash Tobacco Research Institute (Mazandaran). For cultivation, 10-liter clay pots were selected and filled with soil prepared from an alfalfa field, and the pots were arranged according to the experimental design plan in an open area space in the Urmia Tobacco Research Center. Alfalfa is not the host of Orobanche, and its long-term establishment in the field (usually 6 years) does not permit Orobanche seed dispersion in the soil; therefore, the soil should be almost free of Orobanche seeds. In the experiment with Orobanche infection, the soil of the pots, before being filled, was mixed with 0.06 g of Orobanche cernua seeds (containing approximately 12,000 seeds), which were collected from the field of Urmia Tobacco Research Center one year before starting the experiment. In the north-west regions and especially in West Azerbaijan, this type of Orobanche is predominant on the tobacco and is seen more often in the fields. The seedlings of each tobacco genotype were prepared in the bed, and when the tobacco seedlings reached a height of 12 cm, they were transferred to the pots. All agricultural operations, such as transplanting, irrigation, adding soil at the base of the plant, and protecting against pests and diseases during the tobacco growing period, were carried out according to the existing standards for oriental tobacco. The leaves of tobacco genotypes were harvested at the time of industrial ripening (about 45-50 days after transplanting) three times, dried in the sun, and weighed using a digital scale with an accuracy of 0.001 g. The univariate parameters of stability were calculated after individual and combined analyses of variance.
Results: The results of the analysis of variance showed a significant difference among tobacco genotypes for all the studied traits. Moreover, the genotype × environment interaction was significant for all traits, indicating different responses of tobacco genotypes under Orobanche-stressed and non-stressed conditions. Mean comparisons showed that the Orobanche stress reduced the averages of all morphological traits. Stability analysis using methods based on variance and regression analyses revealed that genotypes 45, 33, and 78 had the highest coefficient of variation, indicating the lowest level of stability. Among these, genotype 45 had a mean value higher than the overall mean. Furthermore, genotypes 75, 53, and 41 were identified as stable genotypes due to possessing the lowest stability variance. According to the Plastid and Peterson method (θi), genotypes 75, 55, 53, and 41 showed the lowest θi values. Among these, genotype 53 demonstrated a mean performance higher than the overall average.
Conclusion: By evaluating the stability of genetic materials, stability indices can be highly beneficial for the optimal and efficient selection of parental genotypes to develop high-yielding and stress-tolerant cultivars. Based on different stability methods, genotype 53 is introduced as a stable genotype with optimal performance.
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