Evaluation of genetic diversity of some tea genotypes attributed to Darjeeling in Iran using ISSR markers

Background and objectives: Tea (Camellia sinensis (L.) O. Kuntze) is the most consumed beverage in the world after water and an important commercial plant with economic value in northern Iran. Over the years, various tea plants have been cultivated in Iran's tea gardens by seed method, which has led to a high diversity in them. Since most gardeners have propagated the plant sexually, tea gardens vary in quality. Therefore, determining the genetic diversity and relatedness of plants has an important role to support breeding and breeding programs.

Materials and methods: In this study, 28 tea plants attributed to Darjeeling region along with eight Iranian samples and eight samples imported from Sri Lanka were investigated for genetic diversity using ISSR markers. After sampling from young and fully developed leaves, their genomic DNA was extracted and 16 ISSR markers were used to investigate the genetic relationships of 44 tea samples. The obtained data were analyzed by the simple similarity coefficient for the ISSR markers and the cluster was designed based on the UPGMA algorithm. Population structure analysis was also done by POPGENE program.

Results: The use of 16 ISSR primers produced 158 bands, of which 116 bands showed polymorphism, and based on this, the percentage of polymorphism was calculated as 73.42%. The PIC test showed a range of 0.45 to 0.50 and this indicator was 0.49 for all markers. The results of Cophentic test showed that SM similarity coefficient and UPGMA algorithm are the most suitable for cluster analysis. Based on the obtained data, the range of similarity was found in the range of 0.376 to 0.880 with an average of 0.626. In the cluster analysis, the samples were divided into two groups at the similarity level of 0.56, and the first group is the largest group, which can be divided into two subgroups. In the population structure analysis, the indicators of Observed number of alleles, Effective number of alleles, Nei's gene diversity and Shannon's Information index in populations and total population were calculated as 1.928, 1.641, 0.364 and 0.532, respectively. The total diversity, average intrapopulation diversity, level of population subdivision were also obtained as 0.380, 0.330 and 0.130 respectively. The maximum similarity was between the samples attributed to Darjeeling and selected Iranian samples.

Conclusion: Based on the obtained data, it was determined that there are significant changes among the investigated samples based on the ISSR markers. The percentage of polymorphism and polymorphism information content of the used markers indicated that these markers have a high ability to identify diversity among tea genotypes. Also, the results of this study stated that tea genotypes in Iran have high genetic diversity because they are mostly sexually propagated. This level of variation found between samples suggests that tea from different companies or regions is of better quality, not entirely due to genotype, but rather the ecology in which the tea is grown in terms of climate and soil characteristics, as well as processing technology. At the same time, this genetic difference can be used in breeding studies.