dc.description.abstract | Bacterial wilt (Ralstonia solanacearum) is a devastating disease of tomato that is quickly
spreading and causing reduction in yield and income to farmers in Kenya. The objective
of the study was to determine the effectiveness of tomato rootstock in bacterial wilt
management. Effectiveness of Rootguard® and Nordox® in controlling the diseases was
also evaluated. A survey was carried out in December 2011 in Kirinyaga, Kiambu,
Kajiado and Laikipia counties to collect tomato production information. Information on
production practices, diseases and pest present as well as control practices was gathered
by administering a questionnaire to the farmers in combination with farm evaluation
covering both open field and greenhouse production. The field experiment was carried
out in Kiambu, Ruiru, Karen and Isinya sites in farmers’ greenhouses where previous
crop was affected by bacterial wilt disease. A greenhouse variety Anna F1 was used as a
scion and was grafted on rootstock variety Cheong gang, Shin cheong gang and on a local
wild tomato variety. Efficacy of biological product Rootgard® and a copper fungicide
Nordox® were tested while non-grafted Anna F1 was used as a negative control. The
experiment was repeated under glasshoues conditions. In both field and glasshouse
experiment incidence of bacterial wilt, severity and yield data was collected.
From the survey it was found out that bacterial wilt is the most limitation factor to tomato
production in the counties with highest incidence recorded in Kiambu and lowest in
Kajiado. Higher wilt disease incidence was recorded in green houses as compared to open
field production. Poor agronomical practices were isolated as the important factor that
has contributed to the spread of the disease. Most farmers were found not to practice crop
rotation and planted seedling from their own nurseries which were found to increase wilt
disease incidence. Poor field hygiene and flood irrigation use were also identified to aid
spreading of the disease.
Results strongly indicate that bacterial wilt disease severity and incidence was reduced
when wilt susceptible Anna F1 variety was grafted on Shin cheong gang rootstock.
Grafting susceptible Anna F1 tomato variety on Shin cheong gang variety reduced
bacterial wilt incidence by 95% and on rootstock variety Cheong gang by 92%. A wild
tomato variety also used as rootstock reduced disease incidence by 64%. Bacterial wilt
incidence for the varieties in the experimental sites differed with higher disease levels
being observed in Kiambu and Ruiru and least in Isinya and Karen. The tolerance levels
for each rootstock had a similar trend between the sites. Plants grafted onto Cheong gang
and Shin cheong gang had lowest disease incidence and produced high yield of tomato in
both quantity and quality when compared to non grafted Anna F1. This was true for both
field and glasshouse experiments. Tests on the grafted plants were negative to R.
solanacearum confirming that the pathogen was absent from the plants.
The study indicated that bacterial wilt can be effectively be managed by grafting
susceptible varieties on tolerant rootstock. With high level of tolerance grafted plants can
be planted in fields that are infected with R. solanacearum. Grafting also improved the
performance of the scion resulting in higher yield and better quality fruits than non-
grafted Anna F1. | en_US |