Deutscher Tropentag, October 8 - 10, 2003 in Göttingen "Technological and Institutional Innovations for Sustainable Rural Development"

Agronomic Evaluation of the Cultivated Yam Bean (Pachyrhizus spp. Germplasm under West African Conditions

¹Georg-August-Universität Göttingen, Institute of Agronomy and Plant Breeding, Germany
²Georg-August-Universität Göttingen, Institute of Agricultural Chemistry, Germany
³Georg-August-Universität Göttingen, Institute for Agricultural Technology, Germany

Abstract

The yam bean is a legume root crop usually known as a vegetable crop. Three cultivated species are distinguished: Amazonian yam bean (Pachyrhizus tuberosus), Mexican yam bean (P. erosus) and Andean yam bean (P. ahipa), but interspecific hybrids are fertile and vigorous. The crop might have the potential to be used like soybean and cassava. The 1000-seed weight is high (from 180 to 230 g), seeds have a high protein (26 to 32 %) and oil (22 to 26%) content with about 20% carbohydrates of seed weight. However, for consumption the compound rotenone (about 1% seed weight) has to be extracted or destroyed. Tubers are characterized by high moisture content (usually about 80 % of fresh tuber weight), but Chuin types of P. tuberosus have a low moisture content (about 70 %) and are used like cassava. The tuber includes starch as the main component and has a high protein content (8 to 18% of dry matter). Agronomical data for the yam bean is limited. 34 accession were grown in Benin at two locations - one under drought stress conditions - with and without pruning of reproductive parts. The average tuber yield over both locations ranged from 6 to 45 t ha^-1, 21 to 81 t ha^-1 and 10 to 38 t ha^-1 for the Amazonian, Mexican and Andean yam bean, respectively. In a combined utilization of tubers and seeds tuber yield ranged from 5 to 29 t ha^-1, 10 to 49 t ha^-1, 6 to 27 t ha^-1 and seed yield from 1.5 to 2.9 t ha^-1, 3.5 to 4.6 t ha^-1 and 2.6 to 2.7 t ha^-1 for the Amazonian, Mexican and Andean yam bean, respectively. The tuber dry matter content ranged from 18 % to 36 % of fresh tuber weight with 8 to 14 % raw protein content on dry matter basis. From all species tubers were processed to 'gari' after traditional starch extraction. Moreover, accessions could be made available by CIP Lima / Peru and can be freely distributed from country to country. In conclusion attractive yam beans could be identified for West Africa.

Keywords: Gari processing, agronomical evaluation, Amazonian yam bean, Andean yam bean, legume root crops, Mexican yam bean, neglected crops, Pachyrhizus

Contact Address: Wolfgang J. Grüneberg, Georg-August-Universität Göttingen, Institute of Agronomy and Plant Breeding,  Göttingen, Germany, e-mail: wgruene1gwdg.de