Biochemical analysis on the metabolites from oil palm roots related to ganoderma boninense pathogenesis
Basal Stem Rot (BSR) disease caused by Ganoderma boninense is the most severe disease in Malaysia and other South East Asia oil palm plantations. This disease contributes to significant yield losses and impacts the oil palm industry. To date, there is no promising remedy or reliable detection techni...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2023
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| Subjects: | |
| Online Access: | https://eprints.ums.edu.my/id/eprint/39043/1/24%20PAGES.pdf https://eprints.ums.edu.my/id/eprint/39043/2/FULLTEXT.pdf |
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| Summary: | Basal Stem Rot (BSR) disease caused by Ganoderma boninense is the most severe disease in Malaysia and other South East Asia oil palm plantations. This disease contributes to significant yield losses and impacts the oil palm industry. To date, there is no promising remedy or reliable detection technique for this disease is confidently reported. Therefore, this study aims to investigate metabolites that may contribute to the partial resistance or susceptibility of oil palm to G. boninense . Sixmonth- old oil palm seedlings' roots were elicited with copper sulphate (CuSO4) to investigate the presence of their phytochemical constituents. Oil palm roots were extracted with six different solvents. Among the solvents were methanol, ethanol, acetone, ethyl acetate, chloroform and petroleum ether. The distribution of phytochemicals in six-month-old oil palm roots extracted with different solvents was assessed and compared. The findings suggest that methanol was the best solvent extraction for CuSO4-elicited oil palm roots. It possessed the ability to extract various phytochemical constituents and exhibited the greatest antifungal activities significantly among all the investigated solvents extraction. Meanwhile, a fieldwork study has been conducted to evaluate the level of partial resistance and susceptibility among different commercial oil palm progenies against basal stem rot (BSR) caused by G. boninense . Sixteen-month-old of four different progenies (with different genetic backgrounds) of oil palm seedlings consisting of non-inoculated seedlings served as control and inoculated seedlings with G. boninense colonized rubber wood blocks were screened for the differences. Disease development was observed and recorded as disease incidence (DI) percentage at monthly intervals for the period of nine months. Then, the oil palm roots were harvested at nine months after inoculation for ergosterol content analysis and re-isolation of inoculated and non-inoculated root segments on Ganoderma Selective Medium (GSM) for further confirmation. Results showed that Johor Labis Deli dura x AVROS pisifera (P4) and (Nigerian x Deli) dura x AVROS pisifera (P5) were tolerant progenies. Meanwhile, Banting Deli dura x AVROS pisifera (P1) and (Ulu Remis x Heze) Deli dura x AVROS pisifera (P3) were susceptible progenies. DI was observed as early as four months after inoculation for P1 and P3 compared to P4 and P5 that showed DI at five months after inoculation. DI was gradually increased to 100% for P1 and P3 progenies at nine months after inoculation. Disease severity values for the internal symptoms of bole tissues and accumulation of ergosterol were significantly different and much higher for P1 and P3 in comparison to P4 and P5. The inoculated and non-inoculated crude methanolic extracts of oil palm roots were screened in vitro for antifungal activities using agar dilution technique. The results of antifungal tests among all non-inoculated oil palm progenies crude methanolic extracts showed no significant difference. In contrast, results obtained for inoculated oil palm progenies crude extracts of P4 (23.70%) and P5 (22.96%) gave a significantly higher percent of inhibition in comparison to P1 and P3 that gave significantly weak antifungal activities with a lower percent of inhibition, which is 16.66% and 14.42% respectively. GC-MS analysis of the oil palm roots crude extracts revealed the presence of eight phytocompounds and most with higher abundances of several fatty acids and only two compounds from the phenol group. The compounds are benzoic acid, methyl ester; phenol, 2,6-dimethoxy, 1,4- benzenedicarboxylic acid, dimethyl ester; phenol, 2,4-bis (1,1-dimethylethyl); hexadecanoic acid, methyl ester; 9,12-octadecadienoic acid (Z,Z)-, methyl ester; 9- octadecenoic acid (Z)-, methyl ester and octadecanoic acid, methyl ester. The activities of three defense enzymes including peroxidase (PO), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) were also evaluated. Results showed that at nine months after inoculation the PO, PPO and PAL activity of oil palm roots from the inoculated progenies was higher than that from the non-inoculated. In the inoculated progenies, the PO, PPO and PAL activity of the tolerant progenies was the highest for P4 followed by P5, and that of the susceptible progenies was the lowest for P3 and P1. The PO, PPO and PAL acted as plant active defense mechanisms against the attack of G. boninense . This study has discovered new metabolites that can aid future research efforts related to BSR disease. The compounds produced by the oil palm seedlings could be used as biomarkers to assess the resistance level to G. boninense , which may provide important insights for the early detection of BSR disease in seedling management. |
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