Evaluation Of Sweetpotato Varieties Response To Sweetpotato Virus Disease

Abstract

Sweet potato is an important food, feed and cash crop in Eastern Africa but its productivity is greatly reduced by the sweetpotato virus disease (SPVD). Variety based tolerance to SPVD is a cheap and sustainable way of increasing productivity for smallholder farmers who are the predominant producers. The objectives of the study were to (i) identify the best technology for multiplication and maintenance of healthy sweetpotato planting vines, (ii) evaluate and disseminate farmer-preferred sweetpotato varieties tolerant to SPVD. A study to evaluate the best technology (spraying, maize barrier, control, net and polyethylene cover) to multiply and maintain healthy planting vine was conducted at University of Nairobi Kabete Field Station farm. Sweetpotato varieties were evaluated for tolerance to SPVD in three sites at the coast between May 2006 and February 2007 at Kenya Agricultural Research Institute (KARI)- Mtwapa in Kilifi district and two on-farm sites in Lukore and Mwaluvanga locations, Kwale district. The experimental design in the two experiments was randomised complete block design. Net and polythene covers effectively excluded insect vectors. Spraying kept the population low compared to the maize barrier. A preliminary survey revealed that farmers lacked adequate knowledge on SPVD diagnosis and management. Variety based tolerance was identified among sweetpotato varieties that had farmer and market desired traits. Disease incidence was positively correlated to vector population. The yield of the tolerant varieties was high and stable in seasons and sites. Tolerant varieties had thicker leaf cuticle and longer internodes while hairy varieties tended to be susceptible. Farmers learnt that roguing is a cheap effective way of managing the SPVD disease in both nursery and field. Varieties were disseminated in the region and more than fifty farmers planted them. Dissemination of disease tolerant sweetpotato varieties with desirable traits coupled with building farmers capacity to maintain clean vines can sustain sweetpotato productivity