Elucidating Genetic Diversity among Sour Orange Rootstocks: a Comparative Study of the Efficiency of RAPD and SSR Markers

In order to compare the effectiveness of two molecular marker systems, a set of six RAPD and nine SSR markers were used to study the genetic diversity in a population of 46 sour orange accessions, a common rootstock used in almost all citrus orchards in Tunisia. Genetic diversity parameters [average and effective number of alleles, percentage of polymorphism, polymorphic information content (PIC), effective marker index (EMI), and marker index (MI) parameters] for RAPD, SSR, and RAPD + SSR were determined in order to assess the efficiency of the two marker systems. The results revealed that these parameters were significantly higher when using RAPD markers. Similarly, cluster analysis using the results of RAPD was practically the same as that obtained when combining data from the two marker systems (RAPD + SSR) demonstrating the efficiency of RAPD in discriminating between sour orange accessions. Therefore, the use of SSR markers, known to be more efficient and discriminatory, does not bring significant supplementary information in this work. Indeed, results would have been obtained using only the RAPD markers. Accordingly, this work highlights the efficiency and advantages of RAPD, as an easy and efficient technique, in studying citrus rootstock's genetic diversity, and establishing genetic relationships among citrus accessions.