Recent studies have shown that the basic chromosome number of the three major edible yams, Dioscorea alata, Dioscorea rotundata and Dioscorea trifida, is x = 20, and that the clones with 2n = 40 chromosomes are diploids. D. alata breeding programmes were limited to the production of diploid hybrids until 2006, when the tetraploids (2n = 80) were found to be fertile and polyploid hybrids were produced by conventional hybridisation. However, the nature of the polyploidy (autotetraploidy or allotetraploidy) was not known in D. alata tetraploid clones. In the present study, the inheritance pattern of simple sequence repeat markers was determined in a tetraploid progeny using a Bayesian approach and by examining double reduction events. Results obtained confirm the autotetraploid nature of the 2n = 80 clones of D. alata.