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CROP PROTECTION PROGRAMME: Promotion of and technical support for methods of controlling whitefly-borne viruses in sweet potato in East Africa

Sweet potato virus disease (SPVD) is the main disease of sweet potato in Africa and is caused by dual infection of sweet potato by the aphid-borne virus Sweet potato feathery mottle virus and the whitefly-borne Sweet potato chlorotic stunt virus. Extensive on-farm and on-station trials have shown that some newly-released sweet potato varieties maintain low incidences of SPVD in areas of Uganda around Lake Victoria where SPVD has previously been shown to be prevalent whilst achieving tuberous root yields considerably exceeding those of local checks selected by collaborating farmers. One variety in particular, NASPOT 1, achieved marketable yields about twice that of the local checks. A wide range of attributes of sweet potato were identified by farmers and ranked. Most attributes involved some aspect of the tubers, though drought resistance and, to a lesser extent, pest and disease resistance, were also included as important attributes. NASPOT 1 was ranked highly, primarily because of its big, early yield of large, sweet, mealy tubers. These newly-released varieties are now being disseminated in districts around Lake Victoria. Preliminary results suggest that some are being adopted enthusiastically and farmers with access to the new varieties of sweet potato are increasing production; however, their impact continues to be monitored. In a further set of on-farm and on-station trials in Kanungu District in the western Rift Valley, a very different agroecology, these varieties failed to yield better than the local checks although maintaining resistance to SPVD: a relatively SPVD-susceptible local cultivar yielded similarly or better. In trials around Bukoba in Kagera Region, Tanzanian released varieties also failed to out yield a local, relatively susceptible local cultivar and the Ugandan varieties have been taken through open quarantine to start an extensive trials programme there. Phytosanitation is being tested as an additional control to the use of resistant varieties. Initial results of trials indicate that the epidemiology of SPVD is largely local and consequently local sanitation practices have a big impact. Roguing in just the first month after planting halved the spread of SPVD with no apparent loss in yield. These and other related trials are continuing. Two reports on previous work funded by R6617 as part of the Tropical Whitefly IPM Project were completed. A session on sweet potato viruses was successfully organized at the Fifth Triennial Congress of the African Potato Association, 29th May – 2nd June, 2000 in Kampala, Uganda.

HOW TO CITE

Gibson, R.W. 2002. CROP PROTECTION PROGRAMME; Promotion of and technical support for methods of controlling whitefly-borne viruses in sweet potato in East Africa. Natural Resources Institute, UK.