Evaluating genetic diversity and relationships among agronomic and yield traits in tobacco cultivars using multivariate analysis

Introduction: Tobacco (Nicotiana tabacum L.) is one of the valuable agricultural and industrial crops that little information is available about its diversity. Investigating genetic diversity and knowing the relationships of genotypes is an important factor in implementing breeding programs. Hybrid seed production is one of the most important breeding programs. The production of new varieties can be increased with new sources of genetic diversity. Due to the need for breeders to have large genetic pool of resources to do breeding activities on crops, it seems necessary to identify factors and agronomic traits that affect yield increase and to investigate the genetic diversity and relationships between them. In this regard, this study was conducted with the aim of investigating the genetic diversity, grouping, and relationships of important agronomic and functional traits of tobacco using correlation, cluster analysis, and factor analysis.
Materials and Methods: In this study, 26 Flue-cured tobacco cultivars, including (10 lines and 16 F1 hybrids), were cultivated and studied in the summer of 2025 year in the Tirtash Tobacco Research and Education Center farm in RCBD plan with 3 replications. The agronomic and functional traits studied included: leaf length and width (cm), Leaf numbers, plant height (cm), stem diameter (mm), chlorophyll index, number of days to flowering, leaf area coefficient, leaf shape index, green weight, dry leaf yield, average price and income per hectare. Data variance analysis for all studied traits was performed based on the statistical model of a randomized complete block design in three replications based on the mean of the data. Then, multivariate statistical analyses were used for the obtained data. In order to evaluate association analysis between the studied traits, Pearson's simple correlation coefficients were estimated. Cluster analysis was performed using the square of Euclidean distance and Ward's method. In order to understand relationships between traits, identify common factors on traits, and determine group relationships between variables, factor analysis using the Principal Component Analysis (PCA) and Varimax rotation was used. All statistical calculations were performed using Excel, SAS 9.1, and XLSTAT 2016 software.
Results: The results of the analysis of variance showed that there was a statistically significant difference between genotypes in leaf number and green leaf weight at 5% probability level, and for plant height, chlorophyll, number of days to flowering, dry yield, average price and income, there was a statistically significant difference at a 1% probability level. In other words, there is diversity between cultivars in terms of these traits. Considering that the dry leaf yield trait is considered as the total yield of the tobacco plant and other agronomic traits are related to it, therefore, the existence of diversity in terms of this trait is important and can be used in breeding programs. By examining the correlation analysis between the studied traits, the traits plant height and yield showed a positive and significant correlation with dry yield. Cluster analysis led to the classification of the studied tobacco cultivars into three different groups with 16, 5 and 5 genotypes, respectively. The results of factor analysis based on principal component analysis showed that the first five factors, in total, explained 78.9% of the variation in the total trait data between cultivars.
Conclusion: In general, significant genetic diversity was observed among the different genotypes studied in terms of agronomic and performance traits.