Unravelling the genetic diversity of water yam (Dioscorea alata L.) accessions from Tanzania using simple sequence repeat (SSR) markers

Water yam (Dioscorea alata L.) is among the most cultivated
species used as a source of food and income for small-scale farmers in
Tanzania. However, little is documented about Dioscorea species available
in Tanzania, including their genetic diversity. This study used ten
polymorphic microsatellite markers to determine the genetic diversity and
relationship of 63 D. alata accessions from six major
producing regions. Results revealed a polymorphic information content
(PIC) of 0.63, while the number of alleles per locus ranged from 4 to 12
with a mean of 7.60. The expected heterozygosity ranged from 0.17 to 0.74,
with a mean of 0.49, which suggests moderate genetic diversity
of D. alata accessions. Kagera region had the highest mean number
of (1.5) private alleles. Analysis of molecular variance revealed that 91%
of the variation was attributed to within-population while
among-population contributed 9% of the total variation. The highest
Nei's genetic distance (0.65) was for accessions sampled from Arusha
and Mtwara regions. Principal coordinate analysis and cluster analysis
using Unweighted Paired Group Method using Arithmetic (UPGMA) grouped D.
alata accessions into two major clusters regardless of
geographical origin and local names. The Bayesian structure analysis
confirmed the two clusters obtained in UPGMA and revealed an admixture
of D. alata accessions in all six regions suggesting
farmers' extensive exchange of planting materials. These results are
helpful in the selection of D. alata accessions for
breeding programs in Tanzania.