Retour au sommaireMIGNOUNA H.D., ABANG M.M., WANYERA N., CHIKALEKE V., ASIEDU R., THOTTAPPILLY G. 2005. PCR marker-based analysis of wild and cultivated yams (Dioscorea spp.) in Nigeria: genetic relationships and implications for ex situ conservation. Genetic Resources and Crop Evolution, 52: 755-763.
Abstract :
Reliable characterization of the variation among wild and cultivated yams in Nigeria is essential for improved management and efficient utilization of yam genetic resources. RAPD and double stringency PCR (DS-PCR) analyses were used to investigate genetic relationships and the extent of redundancy among 30 accessions of two cultivated, and 35 accessions of four wild yam species collected from Nigeria.
Twentyfive
selected random decamer and two microsatellite primers were used individually and in combination to
generate DNA profiles for each accession of the six Dioscorea species.
The number of amplified fragments
varied from 7 to 18 fragments per primer/primer combination. Different levels of intraspecific genetic
diversity were found, with Dioscorea rotundata Poir. being the most variable.
Based on identical profiles
for the RAPD and DS-PCR primers, 12 duplication groups consisting of a total number of 37 accessions
were observed in the present study.
An UPGMA analysis grouped the majority of plants according to the
species. Cultivated yams belonging to the D. cayenensis–rotundata species complex, which were classified
into seven morphotypes/varietal groups, could be clearly separated into two major groups corresponding to
D. rotundata Poir. and D. cayenensis Lam. D. cayenensis cultivars exhibited a low level of intraspecific
variation and were genetically close to the wild species Dioscorea burkilliana J. Miège.
D. rotundata cultivars classified into six varietal groups showed a high degree of DNA polymorphism and were separated into two major groups that appeared most closely related to Dioscorea praehensilis Benth. and Dioscorea liebrechtsiana de Wild.
We propose, based on these results, that cultivars classified into D. cayenensis should be considered as a taxon separate from D. rotundata.
The implications of intraspecific variability for the ex
situ conservation of wild and cultivated yam germplasm in Nigeria are discussed.