Genetic diversity of tomato's cultivars assessed through ISSR marker

This study was conducted to investigate the genetic diversity of tomato’s cultivars in Iran. Moreover, the efficiency and the application of ISSR molecular markers in evaluating tomato diversity were assessed.

Ninety-nine tomato cultivars, including previously popular, prevalent and cultivars under study for cultivation in Iran were evaluated. Accordingly, 20 ISSR primers were practiced. DNA isolation were carried out using the fresh leaf samples and then determined the quantity and quality of extracted DNA. After PCR, the amplicons were separated by horizontal electrophoresis. The gels were stained with ethidium bromide and visualized in a UV transilluminator for subsequent analysis in digitalized images. The obtained information was analyzed via statistical software.

Amongst 20 primers were applied, the 17 primers were polymorphic. They have made 275 polymorphic amplicons which size's varied from 250 to 3000 base pair (bp). The average polymorphism rate was 97% and nine primers were 100% polymorphic. Having high polymorphic information content, marker index, effective multiplex ratio, and resolution power, UBC 879 primer was properly effective in differentiating the cultivars. The mean Jaccard similarity coefficient was 0.41. The highest genetic similarity was observed between cv. H1423 and cv. Kimia while the lowest genetic similarity was between cv. Lina and cv. Pil ZTP1; 0.96 and 0.13 respectively. The UPGMA algorithm was applied in cluster analysis based on Jaccard similarity coefficient. This analysis grouped cultivars into five clusters. According to the analysis of molecular variance (AMOVA), the distinction between the formed groups was significant. In this study about 35% of the data variation was explained by the first and second components. The overall grouping pattern of clustering corresponds with principal component analysis. The cultivars were divided into five groups. By providing spatial representation of relative genetic distances among individuals, PCA analysis determined the consistency of differentiation among cultivars. cv. Lina and cv. ZTP8 were placed in one group alone and have the greatest genetic distance from other varieties.

This research claimed that Iranian tomato cultivars to some extent have high genetic diversity. In addition, it has been shown that ISSR molecular markers are appropriate for investigating the genetic diversity amongst tomato genotypes due to generation of high level of polymorphism. Thus, these markers have substantial efficiency in distinguishing tomato genotypes.