Genetic Diversity of Some Tomato Lycopersicon esculentum Mill Varieties in Iraq Using Simple Sequence Repeat (SSR) Markers

This study was conducted to evaluate the genetic diversity among 19 tomato varieties (determinate and indeterminate) cultivated in Iraq using polymerase chain reaction based DNA marker (PCR based DNA markers Simple Sequence Repeats (SSRs). To achieve PCR reactions ,total genomic DNA was isolated from fresh leaves (2 weeks old). The average yields of DNA were in the range of 100-295 ng/μl with a purity ranging between 1.8-1.9. A total of 21 alleles were detected among the tested varieties using 5 SSRs loci distributed on 4 chromosomes of tomato. The molecular size of bands obtained from amplification of SSR products ranged from 121 to 247 bp. Alleles ranged from one in (Tom 8-9, Tom 41-42 and Tom 67-68 loci) to twelve in Tom 49-50 locus. The values of heterozygosity for each locus ranged between 0.63 for Tom 31-32 and 0.89 for Tom 49-50 with a mean value of 0.30. The polymorphic information content (PIC) values for the SSR loci ranged from 0.45 in Tom 31-32 to 0.58 in Tom 49-50 loci with an average of 0.21. Each one of (Tom 8-9, Tom 41-42 and Tom 67-68 loci) produce 0.0 value for both heterozygosity and PIC. The study revealed that, The lowest genetic distance was (0.3244) between varieties Kenanh (lane5) and W arda (lane10), while,the highest genetic distance was (0.9177) between varieties Helam (lane3) and Super marimond (lane 16). The genetic similarity values ranging from (0.0823 to 0.6756) depending upon the genetic distance values that ranging from (0.3244 to 0.9177), indicating the largest diversity with percentage of (32 to 91%) among the tested varieties. The analysis of the obtained results from genetic distances and Neighbor-joining dendrogram (unrooted tree) revealed that, the 19 tested tomato varieties can be grouped into two major groups: first cluster include 9 varieties distributed in two subgroups.The second major cluster include 10 varieties which in turn divided into two subgroups.