Genetic diversity of orange fruit (Citrus sinensis L.) cultivars in Tunisia using AFLP markers

In Tunisia, Citrus sinensis culture is spread especially in Cap Bon region in the North East. It is represented by a large number of varieties. AFLP (Amplified Fragment Length Polymorphism) markers were used in order to study genetic diversity. Thirty accessions representing the majority of orange germplasm were collected from Cap Bon region. AFLP products were analyzed by capillary electrophoresis on an automated ABI Prism 3130 DNA sequencer. Using GeneMapper, AFLP bands were scored, across all genotypes, for presence (1) or absence (0) and transformed into 0/1 binary matrix. A total of 330 of polymorphic markers were revealed using 3 AFLP primer combinations. These markers expressed a high level of polymorphism allowing the distinction of all accessions. Resolving power (Rp) showed a high rate of collective Rp (97.75) with an average of 32.58. The Polymorphism Information Content (PIC) ranged from 0.16 to 0.22 with an average of 0.18 per primer pair. Genetic similarities were estimated basing on Nei and Li’s (1972) formula. The similarity coefficient between cultivars ranged from 0.15 to 0.96 with an average of 0.76. Most of the accessions showed a high degree of genetic similarity. Additionally, the relationship of the cultivars was also estimated using principal coordinate analysis (PCoA); the first three principal axes explained 94.56 of the total variation. Bioinformatic tools were very useful for investigating the genetic diversity of orange genotypes. Results of this study showed that AFLP markers can be useful tool for investigating the genetic diversity of orange genotypes.