Underutilized wild Dioscorea Species Found in the Dry Zone Forests of Sri Lanka

Abstract

Wild germplasm of Dioscorea aculata (syn. Dioscorea pentaphyla) known as Katuala andDioscorea obcuniata known as Hiritala were explored, investigated and characterized from forests of Anuradhapura, Polonnaruwa and Hambantota areas. These species grew vigorously in dry, sandy and stony areas. They were field planted at Aralaganwila and evaluated the performance. Katuala and Hiritala species produced aerial auxiliary bulbils that dispersed naturally. Tubers and aerial bulbils of Katuala were suitable for propagation. Tubers exhibited dormancy for about 5 months and another 5 months from planting to harvesting. Both species produced yams once a year. Planted tubers produced vigorously growing vines and then female flowers and bulbils in about 2 months and male flowers in about 2.5 months. Planted bulbils produced slow growing vines but no flowers, bulbils or under ground tubers in 5 month period. Cultivated germplasm produced bulbils (0.4-0.9 g) along the main stem and lateral stems at about 12-46 cm above the ground level. Katuala and Hiritala species possessed a spiny stem. Succulent aerial parts died off but tubers remained dormant during dry season in yala. They produced shoots with the onset of rains in maha. Characteristic differences of growth and morphology of aerial parts and tubers are given. Tubers of Hiritala species were edible in fresh form and that of both species were cooked and consumed. Dioscorea species inhabited in Sri Lanka are in danger due to urbanization, habitat destructions, unsustainable harvesting, damage by wild animals and lack of protection, replanting or cultivations programs.