Characterization and efficacy of white-rot hymenomycetes in biodegradation of oil palm wood logs and suppression of Ganoderma boninense
Sustainability of oil palm production in South-East Asia is jeopardized by Ganoderma boninense, the causal agent of basal stem rot (BSR) in oil palm. Root-to-root contact is a major mode of disease spread, and oil palm debris left unattended in fields is an important source of inoculum. Amongs...
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| Format: | Thesis |
| Language: | English |
| Published: |
2018
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/76940/1/IPTSM%202018%2010%20-%20IR.pdf |
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| Summary: | Sustainability of oil palm production in South-East Asia is jeopardized by
Ganoderma boninense, the causal agent of basal stem rot (BSR) in oil palm.
Root-to-root contact is a major mode of disease spread, and oil palm debris left
unattended in fields is an important source of inoculum. Amongst several control
methods, expulsion of debris, before replanting is currently being practiced. The
present research investigated potential white-rot hymenomycetes as an
antagonist to degrade Ganoderma infected oil palm log blocks and suppressed
BSR infection pressure by reducing the inoculum spread. A total of 100 fungi had
been isolated from the fruiting bodies occurring naturally on oil palm trunks. Of
them, twenty-five Basidiomycetes were isolated on a Ganoderma selective
medium and identified using internal transcribed spacer (ITS) DNA sequencing.
The potential hymenomycetes were evaluated on their dual characteristics of
biocontrol and biodegradation that could be opted in reducing G. boninense
inoculum during oil palm replantation. Three fungi with potentially higher
antagonistic activity based on percentage inhibition radial growth against G.
boninense, were Pycnoporus sanguineus FBR (84%), Trametes lactinea FBW
(82%) and Grammothele fuligo ST2 (81%). Additionally, Lentinus tigrinus FBJ
G3 and a Rigidoporus sp. STB also invaded sterilized G. boninense colonized
oil palm wood blocks. Colonization of oil palm blocks by these isolates resulted
in mass losses ranging from 66 to 79% after 120 days of biodegradation periods.
During early decay period, P. sanguineus FBR selectively removed the wood
lignin, prior to wood polysaccharides, whereas L. tigrinus FBJG3 and T. lactinea
FBW preferentially degraded the wood polysaccharides prior to lignin
degradation. In contrast, G. fuligo ST2 simultaneously degraded the lignin,
cellulose, hemicellulose and preferentially the starch components deposited
mostly in the parenchymal tissue of the oil palm wood blocks. This phenomenon
was supported with the anatomical and chemical characterization (FTIR) studies.
Scanning electron microscopy revealed the ingression and colonization of fungal
mycelium with clamp connections within wood vessels and parenchymatic
tissues. Besides, formation of boreholes as round spots were apparent, followed by loosening and formation of large cavities on the ray of the parenchymatic cells
as the decay progressed. Based on the pathogenicity and vegetative growth
assessments on oil palm seedlings, seven isolates can be affirmed nonpathogenic
to oil palm seedlings. Out of that, four potential strains (Trametes
lactinea FBW, Pycnoporus sanguineus FBR, Lentinus tigrinus FBJ G3, and
Grammothele fuligo ST2) were selected for mass production on agro-industrial
wastes. Six solid-substrates were tested for mass production of the
hymenomycetes. Amongst them, two solid substrates that yielded optimum
lignocellulolytic enzymes production, namely (1) empty fruit bunches inoculated
with P. sanguineus FBR and (2) combination of rubber wood sawdust and
vermiculite inoculated with the strain of T. lactinea FBW were tested for log
blocks treatment in accelerating the decaying process and recovery of
Ganoderma inoculum. Weight lossess of 64% (T. lactinea FBW), 55% (P.
sanguineus FBR) and 23% (un-inoculated) were obtained after 10 months of log
blocks treatment. Similarly, lowest recovery of Ganoderma spp. was reported in
log blocks inoculated with T. lactinea FBW (21%) and P. sanguineus FBR (33%)
in comparison to that of treated with the formulations alone (without
hymenomycetes). The nursery study supported the in vitro investigation, which
had reported T. lactinea FBW and P. sanguineus FBR as the potential antagonist
against Ganoderma inoculum. Furthermore, production of enormous
lignocellulolytic enzymes owe to their efficient bio-degrading ability. This study
provides great insight of the lignocelluloses degradation mechanisms and
processes by these white-rot hymenomycetes. Additionally, an alternative
biotechnological approach has been identified in degrading infected oil palm logs
thus, reducing Ganoderma inoculum pressure in eco-friendly manner. |
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