Characterization of causal agent of brown spot and use of silicon and manganese for disease management in rice
Brown spot is one of the diseases that became a new threat to rice production and was reported to reduce the yield up to 45% under severe infection. However, pathological related information on this disease is lacking in Malaysia. This study focused on identification of the causal agent throug...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
2016
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| Online Access: | http://psasir.upm.edu.my/id/eprint/67861/1/FP%202016%2062%20IR.pdf http://psasir.upm.edu.my/id/eprint/67861/ |
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| Institution: | Universiti Putra Malaysia |
| Language: | English |
| Summary: | Brown spot is one of the diseases that became a new threat to rice production
and was reported to reduce the yield up to 45% under severe infection.
However, pathological related information on this disease is lacking in
Malaysia. This study focused on identification of the causal agent through
morphological and molecular methods, as well as determination of the effects
of silicon (Si) and manganese (Mn) on disease severity and PR-proteins gene
expression. A total of 15 isolates were isolated, identified and screened with
pathogenicity test before characterized culturally. Two isolates of Bipolaris
oryae and 13 isolates of Exserohilum rostratum were identified based on
morphology and internal transcribe spacer (ITS) region of rDNA. AS.P2 (Gene
bank accession number KT831962) as one of the most virulent isolates in
pathogenicity test was further studied for cultural characterization. Highest
spore production was recorded in T2 (12 h flourescent light + 12 h complete
darkness) and T4 (24 h darkness) cultured on corn meal agar (CMA) with no
significant difference between them (21.67 x 106 spores/mL and 21.50 x 106
spores/mL, respectively). The lowest spore production was shown by cultures
grown on malt extract agar (MEA) (0.83 x 106 spores/mL). Two sources of Si,
namely calcium silicate (CaSiO3) and black rice husk ash (BRHA) were tested
in combination with Mn to determine a cheaper source with the same
effectiveness. Results showed significantly higher value of brown spot index
(BSI) for T1 (control) where no Si and Mn were applied with 41.14%. Addition
of Si and Mn increased 38.65 to 51.25% for grain yield production, if compared
to T1 (control). BRHA showed good performance comparable to CaSiO3 in tiller
number, percentage of filled grains, spikelet number per panicle, panicle length
and 1000 grains weight. Plants treated with Mn showed differential expression
of β-1,3-glucanase and chitinase with β-1,3-glucanase showed the highest
expression at 2 DAI and chitinase at 1 DAI. Similarly, plants treated with Si
showed differential expression of β-1,3-glucanase and chitinase with the
highest expression recorded at 3 DAI and 1 DAI, respectively. This study
found E. rostratum a new causal agent for rice brown spot disease in Malaysia and BRHA has the potential to be a cheaper source of Si to be applied in
agriculture sector compared to CaSiO3. |
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