Cowpea resistance to scab fungus in Uganda: Can resistance be achieved using landraces as source of genes?

Abstract

Cowpea (Viga unguiculata L. Walp), the third most important legume food crop in Uganda is faced with a lot of challenges, paramount among them being scab disease. Mean yield is less than 400 kg/ha though the crop has a yield potential of 3,000 kg/ha. The cowpea scab disease caused by the fungus Sphaceloma sp., is seed-borne and is capable of causing yield losses of up to 100% as the disease affects all the above ground parts of the cowpea plant. There is currently a resurgence of the disease in the country leading to significant yield losses in farmers’ fields, yet none of the five improved cowpea cultivars recently released in the country is resistant to the disease. The use of resistant cultivars in disease management is the most practical approach, easily adopted and more environmentally friendly. A better understanding of the distribution of the disease in the country, identification of sources of resistance; knowing how variable the pathogen is, and, understanding the gene action conditioning resistance to the disease, yield and yield related traits in the crop plant are fundamental to developing resistant cowpea cultivars to manage the disease. This paper reviews information on these important facets to explore the possibility of developing cowpea cultivars with resistance to the scab fungus in Uganda. The literature suggests that breeding for resistance to the cowpea scab disease and high yield can be achieved using Ugandan landraces as source of genes