Status of Under-Utilised Tuber Legumes Yam Bean and Wild Cow Pea in Indonesia

Abstract

The yam bean (Pachyrhizus spp.) was introduced to South East Asia in 16th century from America. It has received more interest since the Amazonian yam bean Chuin has been found which is used and processed like cassava. The wild cow pea (Vigna vexillata) is used in Asia, Africa and Central America for its tuberous roots. The objectives of this study were to record the cultivation status as well as the use and processing knowledge of these species in Indonesia. In a collection trip a questionnaire was used to record these information. 110 yam bean (P. erosus) and four cultivated V. vexillata accessions were collected. The yam bean — local names: Bengkuang, Uas or Bose — is cultivated on all major Indonesian islands. Cultivated Vigna vexillata — local names: Jempirang — has been found only in Bali. Personal communications indicated that there is also cultivation in Timor and Papua. The yam bean is known as vegetable crop rather than as root crop. It is consumed raw as salad or as refreshing tuber fruit. The Jempirang is considered as a root crop-tubers and is always steamed or boiled before consumed and seeds are additionally used. Yam bean yields are 10 to 70 t ha−1 in West Indonesia (Sumatra and Java) compared to 10 to 50 t ha−1 in East Indonesia (Sulawesi, Timor, Flores and Sumba). In East Indonesia it is predominantly intercropped with maize and cassava due to poor soil conditions. The Jempirang yields are 20 to 30 t ha−1. It is cultivated after rice (Oryza sativa) in the dry season. In conclusion the Jempirang should consider more attention as a legume root crop and merits further investigations e.g. crossings with V. vexillata var. lobatifolia from the Namibian drylands. Furthermore, the yam bean should be considered as an additional option for intercropping systems. A higher dry matter Amazonian yam bean — so called Chuins — are lending themselves as a protein rich starchy stable as well as incorporation of high dry matter into the South East Asian yam bean genepool. The differences between these genepools are currently under investigation. Keywords: Neglected crops, legume root crops, yam bean, Pachyrhizus, wild cowpea, Vigna vexillata