The lesser yam Dioscorea esculenta (Lour.) Burkill: a neglected crop with high functional food potential

International audience

English. In the humid tropical zone, there is a growing need for staple crops diversification and for alternatives to cereals. The lesser yam (Dioscorea esculenta (Lour.) Burkill), also known as the Asiatic yam, presents the highest agro-economic potential among the minor yam species. Here, we clarify the taxonomy and review research on the phylogeny, cytology, germplasm characterization and conservation, in vitro culture, virology, agronomy and nutritional composition of D. esculenta. The species is genetically distant from all the other cultivated yams and is the sole representative of the section Combilium. Diploids (2n = 40), triploids (60) and tetraploids (80) exist but higher number of chromosomes are also reported. Except in India, Vietnam and the Philippines, very few accessions are preserved in ex situ collections. In vitro preservation is feasible and the percentage of surviving cultures of D. esculenta is not significantly different to major yam species. The crop is free of major pests and diseases compared to other cultivated yams and if 13 viruses have been detected, their incidence is asymptomatic. When plants are staked, yields of 30-40 t/ha are frequent. The attractive shape of its small tubers and its extremely thin skin are assets for urban consumers. They are rich in secondary metabolites including phenols, flavonoids, allantoin, inulin and saponins with well documented physiological properties. The lesser yam has potential as a high valued functional food. Surprisingly, no DNA marker research has been conducted to assess the allelic diversity of the species and there are no breeding activities to strengthen its potential. Future research directions are discussed.