ISSR molecular marker was used to investigate genetic diversity of Dare Gazi genotypes of Mashhad Esteghlal orchard and its relationship with other commercial and native cultivars of pear. Among Dare Gazi genotypes of Mashhad Esteghlal orchard 23 genotypes were selected base on difference in tree vigor, leaf color, shape and color of fruit and also 33 other commercial and native pear cultivars from Esteghlal orchard and other Mashhad commercial orchards were studied. A total number of 230 DNA fragments were obtained using 11 primers of which 225 were polymorphic. On average, each primer produced 20.9 bands. Dice similarity coefficient ranged from 0.27 (between Dom Kaj and Asian pear) to 1 (between Dare Gazi 1 and 2 genotypes). Sample cluster dendrogram indicated that 56 genotypes were divided into 12 distinct clusters. The dendogram generated on the principle of Unweight Pair Wise Method using Arithmetic Average (UPGMA) was constructed by Dice coefficient and the genotypes were grouped into 12 clusters. Dare Gazi genotypes did not show 100% similarity due to seed propagation or mutation, as Dare Gazi 3 and 18 genotypes had the lowest similarity coefficient (0.64). Asian pears were placed in a separate group from European pears. And Dare Gazi genotypes from different orchards were grouped separately, but all of them are called as Dare Gazi pear for convenience. ISSR molecular marker can well identify the genetic variability among genotypes and cultivars and found suitable for grouping them.

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