Assessment of genetic diversity in two Allium spp. using random amplified polymorphic DNA markers

Abstract

Genetic diversity was estimated among fifteen local cultivars of two Allium species (14 ofAllium cepa and 1 Allium ascalonicum) using 6 random amplified polymorphic DNA (RAPD) primers. A total of 54 RAPD amplicons were obtained, of which 25 (46.3%) were polymorphic. The percent polymorphism between primers ranged from 6.9 to 30.2%. The highest genetic distance (75%) was observed between light brown and white phenotypes.A. ascalonicum produced a distinct banding pattern from all other 14 genotypes belonging to A. cepa. Genetic diversity within and between the four phenotypic (colour) classes showed that highest variability exists within the purple cultivars. Nei’s gene diversity ranged from 0.11 ± 0.19 in the light brown phenotypic groups to 0.27 ± 0.18 in the purple group. The observed number of alleles was 1.79 ± 0.41 and effective number of alleles was 1.46±0.35 for the purple phenotype, while 1.27±0.45 and 0.19±0.32 alleles represent the observed alleles and effective number of alleles in detecting polymorphism the light brown phenotype, respectively. Dendrogram constructed from similarity coefficient produced three clusters. The On8 and On10 cultivars from Borno and Kebbi states respectively were the closest probably as a result of exchange of genetic materials between farmers and for commercial purpose being an open pollinated crop, while On16 and On17 clustering together may be due to collection from same location and adaptation to the environment. Results are discussed in the light of current taxonomic delineations which consider A. ascalonicum as a subspecies of A. cepa. Interspecific Hybridization between A. cepa and A. ascalonicum is encouraged in order to introduce medicinally active compounds like flavonoids into A. cepa. Key words: Allium cepa, Allium ascalonicum, genetic diversity, Nigeria, random amplified polymorphic DNA (RAPD).