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Viruses limit sweetpotato (Ipomoea batatas) production worldwide. Many sweetpotato landraces in East Africa are, however, largely virus‐free. Moreover, some plants infected by the prevalent Sweet potato feathery mottle virus (SPFMV) may be able to revert to virus‐free status. In this study, we analysed reversion from SPFMV, Sweet potato virus C, Sweet potato mild mottle virus, Sweet potato chlorotic stunt virus (SPCSV) and Sweet potato leaf curl Uganda virus using the indicator plant I. setosa and PCR/reverse‐transcriptase PCR. We also investigated environmental factors (temperature and soil nutrients) that may influence reversion from virus infection. We tested reversion in the East African cultivars New Kawogo, NASPOT 1 and NASPOT 11, and the United States cultivars Resisto and Beauregard. Reverted plants were asymptomatic and virus was undetectable in assayed parts of the plant. After graft inoculation, only the East African cultivars mostly reverted at a high rate and from most viruses though cultivar Beauregard fully reverted following sap inoculation with Sweet potato virus C. None of the tested cultivars fully reverted from single or double infections involving SPCSV, and reversion was only observed in co‐infections involving potyviruses. Root sprouts derived from SPFMV‐reverted plants were also virus free. Reversion generally increased with increasing temperature and by improved soil nutrition. Overall, these results indicate variation in reversion by cultivar and that the natural ability of sweetpotato plants to revert from viruses is malleable, which has implications for both breeding and virus control. [ABSTRACT FROM AUTHOR]

Sweet potato feathery mottle virus ( SPFMV) and Sweet potato chlorotic stunt virus ( SPCSV) are the most common viruses infecting sweetpotato in Uganda. Field plots planted with graft inoculated plants of virus-free cultivars Beauregard, Dimbuka, Ejumula, Kabode and NASPOT 1 were used to assess the effect of SPFMV and SPCSV on yield and quality of sweetpotatoes in two agro-ecologies. SPFMV spreads rapidly to control plots at Makerere University Agricultural Research Institute Kabanyolo ( MUARIK), and these plots had similar yields to those singly infected with SPFMV but at the National Semi Arid Resource Research Institute (Na SARRI) where SPFMV spreads slowly, plots infected with SPFMV yielded 40% less than the control. Recovery from SPFMV appeared to be more frequent at Na SARRI than at MUARIK. Infection by SPCSV alone resulted in yield losses of 14-52%, while mixed infections of SPFMV+ SPCSV resulted in yield losses in both locations of 60-95% depending on the cultivar. SPCSV and mixed infections of SPFMV+ SPCSV also reduced the number of roots formed as well as the diameter of the roots, resulting in a greater length to diameter ratio compared to the healthy control. This study, therefore, confirms that both SPFMV and SPCSV, both singly and when mixed, can reduce yield, the extent depending on the cultivar. To mitigate the effect of these viruses, farmers should use clean planting materials of resistant varieties. [ABSTRACT FROM AUTHOR]

The article describes the NASPOT 11 sweetpotato variety cultivated through a participatory plant-breeding approach in Uganda. The cultivar was approved for release by the Ugandan Plant Variety Release Committee in April 2010. The cultivar contribute to food security in the farming and food system in the country. A chart is presented that shows the performance of the cultivar in on-farm sweetpotato participatory breeding trials from 2005-2008 in the country.