Molecular characterization of sour orange (Citrus aurantium) accessions and their relatives using SSR and SRAP markers

Citrus production with its many varieties is of importance since it provides economically important products for Turkish exports. Sour orange is a rootstock commonly used for propagating the different scion varieties. Knowledge of the genetic diversity of the rootstock accessions would be useful in order to improve citrus breeding programs. We studied genetic relationships and diversity of 51 accessions of sour orange (Citrus aurantium) and their relatives using SSR (simple sequence repeat) and SRAP (sequence-related amplified polymorphism) molecular markers. Twenty-one SRAP primer combinations were tested on these accessions and relatives, producing 167 polymorphic fragments, with a mean of 8.0 and a mean polymorphism information content value of 0.47. Seventeen SSR primers also produced 30 polymorphic fragments, with a mean of 1.4 per primer and a mean polymorphism information content value of 0.39. The unweighted pair-group method with arithmetic average analysis using combined SSR and SRAP data showed a similarity range from 0.71 to 1.00 among the accessions. In the cluster analysis, sour orange relatives were indicated as a separate group from sour orange. 'Macrophylla' and 'Mexican lime' were the accessions most distinct (0.71) from the others. We conclude that genetic diversity in these sour orange accessions is lower and some of them were identical.