Antagonistic Activities of Epiphytic Bacteria on Black Pod Disease of Cocoa
A study was conducted to determine the antagonistic activity of epiphytic bacteria isolated from cocoa pod surface on Phytophthora palmivora (Butler) Butler, the causal agent of black pod disease of cocoa. Out of 233 isolates of epiphytic bacteria obtained from non symptomatic and diseased cocoa...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2004
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/41/1/1000548955_t_FP_2004_43.pdf |
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| Summary: | A study was conducted to determine the antagonistic activity of
epiphytic bacteria isolated from cocoa pod surface on
Phytophthora palmivora (Butler) Butler, the causal agent of black
pod disease of cocoa. Out of 233 isolates of epiphytic bacteria
obtained from non symptomatic and diseased cocoa pods, only
were found to have antagonistic activities against the fungal
pathogen when screened by the dual-culture method. Three
isolates, (LKM/B/1, LKM/B/35, LKM/B/76c) were identified as
Pseudomonas putida Biotype A, 2 isolates (LKM/B/5 and
LKM/B/62b) were identified as Pseudomonas aeruginosa and
one isolate each was identified as Pseudomonas spinosa
(LKM/B/2), Burkholderia glidioli (LKM/B/4) and Burkholderia sp
(LKM/B/6). Identification of the epiphytic bacteria was done using
the BIOLOG® Identification System. Percentage inhibition of the
radial growth (PIRG) of P. palmivora by the epiphytic bacteria
ranged from 66.0% to 82.1%. All isolates of epiphytic bacteria
showed optimum antagonistic activities at 300 C. pH has no
influence on the antagonistic activities of the epiphytic bacteria.
Detached pod studies showed that pods treated with the
epiphytic bacteria retarded the growth of black pod lesion up to
12 days after inoculation.
Isolate Burkholderia glidioli (LKM/B/4), Pseudomonas aeruginosa
(LKM/B/5) and Pseudomonas putida Biotype A (LKM/B/76c)
produced volatile substances that affect the growth of P.
palmivora, while isolates LKM/B/1 and LKM/B/35 of
Pseudomonas putida Biotype A and isolate LKM/B62b of
Pseudomonas aeruginosa did not show the production of volatile
substances. Isolate LKM/B/76c also produced diffusible
metabolites that could significantly inhibit the growth of P.
palmivora compared to other epiphytic bacteria especially isolate
LKM/B/35 which showed good antagonistic through dual culture
method.
Microscopic observations of P. palmivora at the periphery of the
inhibition zone indicated that all isolates of epiphytic bacteria
inhibited P. palmivora by the process of cell wall degradation and
growth retardation. |
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