Abstract:
Sweet potato is a food and cash crop in the coastal region of Kenya but the sweetpotato virus disease is also
prevalent in the area. Selection of sweetpotato varieties resistant to SPVD and with desirable consumer traits is an
economically feasible strategy that can sustain sweetpotato production. Seventeen sweetpotato varieties were screened
for resistance/tolerance against sweetpotato virus disease in three sites in Coastal Kenya. The experimental design was
complete randomised block design replicated three times in the three sites. Disease incidence and vector populations
were assessed using standard procedures. The sweetpotato virus disease (SPVD) was present in the three sites and
varied across sites and among sweetpotato varieties. In the first season disease pressure (%) was highest in Lukore and
lowest in Mtwapa while in the second season it was highest in Mtwapa and Lowest in Mwaluvanga.Varieties, jewel and
440015 were the most susceptible across the three sites while Jonathan, Zapallo and Japonese proved to be resistant
across the three sites in both seasons. The disease incidence (%) was lower in the first season than in the second season
and the most susceptible cultivars were the most affected. There was a negative relationship between disease incidence
and tuber yield and as well between harvest index and the root dry matter (%). The number of whiteflies varied across
the sites with Lukore recording the highest number and Mtwapa the lowest in the first season with no significant
difference in the second season. No aphids were observed in the three sites in both seasons. A breeding program should
be put in place to breed for sweetpotato virus disease (SPVD) resistance varieties with consumer preferable traits in the
region. There is need to establish the physiological basis of resistance in the resistant sweetpotato varieties.
