Effects of naturally occuring phenolic compound on cell wall degrading enzymes and suppression of Ganoderma boninense infection in oil palm seedlings
Palm oil is one of the major sources of edible oil in the world with 85% of it being produced by Malaysia and Indonesia. However, the production is greatly hindered by the basal stem rot (BSR) disease. The causal pathogen of BSR disease is Ganoderma sp. Ganoderma boninense, the causal pathogen...
Saved in:
| Main Author: | |
|---|---|
| Format: | Thesis |
| Language: | English |
| Published: |
2018
|
| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/77021/1/IPTSM%202018%204%20-%20IR.pdf |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Summary: | Palm oil is one of the major sources of edible oil in the world with 85% of it
being produced by Malaysia and Indonesia. However, the production is greatly
hindered by the basal stem rot (BSR) disease. The causal pathogen of BSR
disease is Ganoderma sp. Ganoderma boninense, the causal pathogen of
BSR in oil palm is white rot basidiomycetes. This pathogen infects oil palm
primarily via roots by degrading the lignin and cellulose components.
Therefore, understanding the mode of infection of G. boninense in oil palm
would be advantageous. An alternative solution to control the emergence of
BSR is to inhibit the lignolytic and the cellulolytic enzymes of G. boninense.
The phenolic compounds present naturally in the plants play a critical role in
the pathogen elimination, signaling, increasing the resistance and the lignin
biosynthesis. Hence, ten naturally occurring phenolic compounds namely,
benzoic acid, coumaric acid, 2,6-dimethoxyl benzoic acid, 2,6-dimethoxyl
phenol, guaiacol, ferulic acid, pyrocatechol, salicylic acid, syringic acid, and
vanillic acid were selected to evaluate their potential to inhibit G. boninense. In
this study, the phenolic compounds were tested for their ability to inhibit the
growth of G. boninense and their inhibitory effect towards the production of
lignolytic and cellulolytic enzymes. Further, their efficacy was tested to
suppress the BSR infection in oil palm seedlings. The ten selected phenolic
compounds were able to inhibit the growth of G. boninense with different
degrees depending on their concentrations. Microscopic observations revealed
that mycelia growing on media containing phenolic compounds showed
deterioration. A significant (p ≤ 0.05) decrease in the production of lignolytic
enzymes, as well as celluase, amylase and xylanase of about 40-100% was
identified. Except benzoic acid all the other phenolic compounds increased the
secretion of lignolytic and cellulolytic enzymes at 1 mM concentration.
However, as the concentrations increased more than 1 mM the inhibition increased. The enzyme inhibitions have been further quantified and the type of
inhibition was analysed along with their physicochemical properties. Most of
the selected phenolic compounds inhibited the enzymes as uncompetitive or
noncompetitive inhibitors. The lignolytic enzymes were active over a wide
range of temperature from 40-80ºC but sensitive to pH at 6. The cellulolytic
enzymes are more stable in a wide range of pH from 3 to 8 and temperature
40-80ºC when compared to the lignolytic enzymes. The wood degradation
assay suggested that the G. boninense is a sequential degrader of lignin and
cellulose components. The selected phenolic compounds significantly reduced
the degradation rate upto 100% when compared to the control. This was due to
their ability to inhibit the lignolytic and cellulolytic enzymes of G. boninense.
Significant reductions in the disease progression upto 100% were observed in
the oil palm seedlings treated with benzoic and salicylic acid. The oil palm
seedling treated with benzoic and salicylic acid increased the growth
parameters such as height, diameter of the stem, chlorophyll content, root and
shoot weight. In addition, the oil palm seedlings treated with phenolic
compounds showed increased lignification of four percentages. This was due
to the increased activity of phenylaline amino- lyases, peroxidase and
polyphenol oxidase by 1.5 folds. These enzymes are known to be involved in
lignin biosynthesis pathway. The benzoic acid and salicylic acid tested are the
processors for the synthesis of lignin. The findings of this study could be useful
for developing new strategies in controlling the spread of disease, which may
reduce the BSR disease severity in oil palm areas of production. |
|---|