Phenetic characterization of plum cultivars by high multiplex ratio markers: Amplified fragment length polymorphisms and inter-simple sequence repeats

Variability of commercial plum (Prunus L. sp,) cultivars is unknown since b reeding often involves intercrossing hybrids with several species but has b een based on a low number of parents. Molecular markers like amplified frag ment length polymorphisms (AFLP) and inter-simple sequence repeats (ISSR), which sample multiple loci simultaneously, have become increasingly popular , and mere used to characterize 24 diploid and four hexaploid cultivars of plum. Seven AFLP and six ISSR primers were used, and resulted in amplificat ion of 379 and 270 products, respectively, Unweighted pair-group method wit h arithmetic averages (UPGMA) dendrograms, based on similarity coefficients , reflected a clear separation between diploid and hexaploid plums, Among d iploid plums, two pairs of cultivars were relatively distinct from the rest , namely 'Golden Japan' and 'Methley' and 'Ozark Premier' and 'Songold', Fu rthermore, several cultivars were grouped together both with AFLP and ISSR analysis: I) 'Ambra', 'Red Beaut', and 'Black Beaut', 2) 'Black Diamond' an d 'Royal Diamond',3) 'June Rose','Santa Rosa', and 'Royal Red', and iv) 'Fr eedom','Larry Ann', and 'Queen Rosa'. Although the phenetic classification obtained by the two methods were similar (r = 0.73, for the diploid group), ISSR had a higher reproducibility and percentage of polymorphisms (87.4% v s. 62.8%) than AFLP. Methodological aspects of both markers systems are dis cussed. Results obtained suggest that the AFLP and ISSR approaches are valu able tools for identification of specific genotypes and analysis of pheneti c relationships in plum.