Abstract:
Bacterial soft rot, caused by Pectobacterium carotovorum is a disease
responsible for severe post-harvest losses of carrots in Sri Lanka. The
present study aimed to isolate P. carotovorum strains from diseased carrot
samples from different carrot fields and to determine their pathogenicity on
selected vegetable crops. Five bacterial strains, namely CSR1, CSR2,
CSR3, CSR4 and CSR5 were isolated from diseased carrots and their
identity was confirmed using standard biochemical characteristics of P.
carotovorum. All isolates were positive for catalase test, citrate test and
Voges Proskauer test. Each of the isolates showed a luxuriant growth on
McConkey agar and they were negative for oxidase, indole and methyl red
tests. Pathogenicity of each of the isolates was evaluated by inoculating
them on healthy carrot discs. Furthermore, healthy samples of four other
vegetables, namely radish, cabbage, potato and pumpkin were inoculated
with the isolated P. carotovorum strains to study the development of rotting
symptoms at 25°C within 48 hours. CSR1 was able to macerate radish,
cabbage and pumpkin. CSR2 caused rotting symptoms only in radish.
Cabbage and radish were rotten by CSR3 while potato and cabbage did not
show any rotting symptom when inoculated with CSR3. The strain CSR4
was able to macerate all four vegetables tested. Potato was the only sample
that was macerated by CSR5.
