MSc

Bacterial wilt of tomato caused by Ralstonia solanacearum (Smith)
Yabuuchi et al. has continued to be a perennial problem due to its complex
interaction with soil. Hence a study has been taken up to isolate a potent biocontrol
organism and to develop a strategy by integrating the selected control methods so as
to have a sustainable eco-friendly tomato production.
The pathogenic bacterium R. solanacearum was isolated from four different
locations and the characterization studies revealed that the four isolates of the
pathogen belong to R. solanacearum race 1 biovars3. The antagonistic bacterium
isolated from the central zone was capable of producing abundant bluish green
diffusible fluorescent pigment and a non diffusible non fluorescent brown pigment
in King's B medium. Based on the physiological and biochemical studies, this
bacterium was tentatively identified as Pseudomonas aeruginosa.
Seed treatment - with _ antagonistic bacterium facilitates earliness ID
germination and better plant VIgOur in both Pusa Ruby and Sakthi varieties
compared to other treatments, Data on solarisation studies also showed that
solarisation for 30 days has a weak effect in checking the R. solanacearum
population.
In bioassay studies garlic 10 per cent and the Copper fungicides, Bordeaux
mixture 1 per cent and Copper hydroxide 0.15 per cent were sensitive to
Risolanacearum but insensitive to P. aeruginosa.
In pot culture studies, the seeds of the resistant variety Sakthi treated with
beneficial agent, garlic drenching or Bordeaux mixture drenching were found to be
superior to all other treatments in reducing the wilt incidence.

In the main field, treatment combinations were tried based on the results of
pot culture experiments. The rate of increase in wilt incidence was highest in the
early stages and at flowering stage. The plants withstand bacterial infection upto
flowering stage because of the resistant mechanism present in the variety Sakthi.
The result of the study indicated that the bacterial disease of tomato could be
effectively managed by integrating indigenous antagonistic activity of P. aeruginosa
and selective bactericides like garlic extract or Copper hydroxide 0.15 per cent along
with the host resistance of variety Sakthi.