Abstract

Genetic diversity characterization among Dacryodes edulis accessions is important in developing genetically diverse and superior cultivars. This study assessed the genetic diversity of three D. edulis provenances used in controlled breeding trials at ICRAF-Cameroon based on SSR marker technique. Genomic DNA isolated from individual D. edulis samples were primed with six SSR primers (CB09, LD06, CG11, LB12 CE09 and CC01), amplified through PCR and the products resolved using the ABI 3730 DNA analyzer. Alleles using the Gene Mapper software were called. The polymorphism information content (PIC), gene diversity and heterozygosity estimates were computed by using PowerMarker software while GenAlEx software was employed to estimate gene flow levels, to reveal partitioning of variation across the populations and display the genetic relationships among the populations. DARwin software was used to construct a dendogram that also displayed the genetic relationships among the populations. Analysis of Molecular Variance (AMOVA) was used to assess the structure of genetic diversity among provenances. All the 6 primer pairs used in this study were polymorphic. Gene diversity values were calculated for all analyzed loci ranged from 0.2763 to 0.8846 for the loci CG11 and CE09, respectively, with a mean of 0.5851. Heterozygosity values ranged from 0.0220 and 0.5385 for the loci CG11and LD06, respectively, with an average of 0.3132. A significant low level of genetic differentiation (FST = 0.018, p=0.01) was detected among the populations. AMOVA analysis indicated that only 2% of genetic variation existed in populations. The neighbor (joining tree) and PCoA analysis could not reveal a clear separation between populations. Consequently, this study established that the high common level of gene flow obtained could help in maintaining low genetic differentiation and closing genetic relationships of D. edulis populations. Thus introgression of new alleles may be required to broaden the genetic base of the D. edulis provenances. This study also highlighted the need of isolation and characterization of more DNA markers in D. edulis and their uses in advanced studies such as gene discovery, trait linked marker assisted selection and gene mapping.

Key words: Controlled breeding, DNA markers, gene flow, heterozygosity, provenance.