Genetic diversity in ber (Ziziphus spp.) revealed by AFLP markers

Abstract

SummaryBer (Ziziphus spp.), belonging to the buckthorn family Rhamnaceae, is an important fruit crop that grows naturally in harsh environmental conditions. Commercial cultivars have been developed in India, mostly through selection of productive natural variants propagated by budding on wild rootstocks and used for orchard plantations. There is a complete lack of information on the extent of genetic diversity in this fruit crop. In the present study, 33 accessions of cultivated Z. mauritiana (Lam.) and eight accessions of its wild relative Z. nummularia (Burm.f.) Wight & Arn. were investigated using AFLP. Eleven primer pairs used in AFLP analysis detected 952 fragments, of which 789 (83.8%) were polymorphic. Similarity coefficients ranging from 0.14 – 0.86 suggested that the 41 Ziziphus accessions used in this study were divergent. The wild relative being used as a rootstock showed greater diversity than the cultivated species. The range (0.37 – 0.86) and average (0.62) similarity among the 33 cultivated species accessions indicated the broad genetic base of the commercial cultivars. Cluster analysis revealed the complete separation of the 33 cultivated species accessions and the eight wild species accessions into two distinct groups. Morphologically similar cultivars clustered together with a high degree of similarity. A high correlation of the similarity matrix using a single primer combination with that based on all eleven primer combinations suggested that one or a few primer combinations could be used to estimate diversity in ber. Nine primer combinations detected 86 accession-specific amplified fragments and each primer combination gave a discrimination rate of 1. Any of these primers can thus be used to maintain the quality of both scions and rootstocks to establish productive orchards.