Bio-Efficacy of Compost Extracts for the Control of Choanephora Wet Rot Okra (Abelmoschus Esculentus L.)
Bio-efficacy of aqueous extracts prepared from rice straw (RST) and empty fruit bunch of oil palm (EFB) composts for the control of Choanephora wet rot of okra (Abelmoschus esculentus L.) was studied. The physiochemical and microbiological properties of both the finished composts showed that they...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2005
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/6182/1/FP_2005_13.pdf |
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| Summary: | Bio-efficacy of aqueous extracts prepared from rice straw (RST) and empty fruit
bunch of oil palm (EFB) composts for the control of Choanephora wet rot of okra
(Abelmoschus esculentus L.) was studied. The physiochemical and
microbiological properties of both the finished composts showed that they were
within the range of compost standards. RST compost extracts has higher N, PI
K content of 1.14, 3.36, and 1.42 % with respect to EFB extract with 1.01. 2.51,
and 1.20 %, respectively. The aqueous extracts produced therefore are suitable
as foliar sprays for the improvement of growth of okra plants. Twelve days of
brewing was the best extraction time based on the properties of the compost
extracts obtained and their ability to inhibit the growth of C. cucurbitarum in vitro.
The percent germination was reduced by 80 to 83 % in the presence of RST and
EFB extracts. The effect was further demonstrated by using filter (0.2 pm) and
heat - sterilized extracts (autoclaving at 121'~ for 20 minutes) for assessing
their potential effect on mycelial growth, conidial germination of C. cucurbitarum
and production of inducible resistance related compounds in pre - treated
plants. Non - sterilized extracts from both composts gave significantly reduced
(P 10.05) mycelial growth of C. cucurbitarum (84 and 79 % for RST and EFB
extracts, respectively) and enhanced host resistance through production of
inducible compounds such as total phenols, peroxidase (PO), polyphenol
oxidase (PPO) and phenylalanine ammonia lyase (PAL) in okra plants. The
eficacy was perceptibly reduced by filter sterilizing the RST and EFB extracts to
57 and 55 %, respectively, whereas heat sterilization nullifies their activity totally,
suggesting that the activity of both extracts were biological in nature. The higher
activity of filter-sterilized extracts associated with mycelial growth inhibition and
percentage disease reduction as compared to heat - sterilized extracts infers
that chemical factors and nutrient composition of the extracts also played a role
in the activity. Humic acids (active component of humic substances in compost)
extracted from RST and EFB compost extracts when tested in vitro reduced
mycelial growth of C. cucurbitarum by 100 and 64.2 % at 1 % concentration,
respectively. The bio-efficacy was further enhanced by fortifying the extracts
with T. harzianum, an established biocontrol agent against many pathogens.
Trichoderma - fortified extracts (3 x l ~ - ~ cmf ul-') from RST when tested on okra
in glass house and field conditions showed significant increase in plant growth
and yield. There was reduction of 91.9 % in Choanephora wet rot of okra at 12
weeks of assessment in field and was comparable to Dithane M- 4503 and
significantly higher to T. harzianum fortified EFB extracts. |
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