The 2012 ASHS Annual Conference

Species of the vine cactus Hylocereus are increasingly being grown in Israel as new exotic fruit crops that are particularly suited to cultivation in semi-arid and arid lands. Hylocereus species are characterized by high genetic variability; in the current study, we investigated genetic similarity and distance, genetic relationships, allele frequency and polymorphic information content (PIC) of 15 accessions belonging to four commercially important Hylocereus species. As a first step in defining the above genetic characteristics of the investigated accessions, five amplified fragment length polymorphism (AFLP) primer combinations were used. These five sets of primer combinations amplified different subsets of restriction fragments. For each primer, 59 to 91 bands were identified that independently revealed similar patterns for relationships among the species under analysis. About 94.5% of the total number of bands developed were polymorphic, with the majority of the bands being small in size, i.e., between 50 and 250 bp. The highest similarity was found between accessions 96–664 and 96–680, and the lowest, between accessions 88–023 and 96–664, with all four accessions belonging to the species H. megalanthus. PIC varied between primers from 0.27 to 0.37 and between species from 0.40 to 0.50, revealing a high level of heterozygosity. Grouping of the accessions showing high similarity produced four main clusters. Two points of interest emerged: (i) The H. undatus accession 70–02–04 belonged to the cluster of H. megalanthus accessions, which suggested that this H. undatus accession is a putative natural hybrid, and (ii) H. undatus accession 89–024 and H. megalanthus accession 88–023 were clustered in the same node, showing a close association between them, with more than 50% of similarity. From the genetic distance analyses three clusters were obtained; one cluster including three H. monacanthus accessions, one H. costaricensis accession, and two H. undatus accessions (but not 89–024 and 70–02–04); one cluster comprising accession 89–024 (H. undatus) and accession 88–023 (H. megalanthus); and one cluster comprising six H. megalanthus accessions and H. undatus accession 70–02–04. The AFLP study thus confirmed the high genetic variability among Hylocereus species and showed that the technique provides an efficient means for assessing genetic relationships. The study also confirms the excellent prospects for conserving and domesticating these exotic fruit crop species.