Thiamine or vitamin B 1 comprises a pyrimidine moiety and a thiazole moiety. Thiamine pyrophosphate (TPP), the active form of thiamine, acts as a cofactor for various major enzymes, for example, transketolase (TK), α-ketoglutarate dehydrogenase (KGDH) and pyruvate dehydrogenase (PDH). It is suggested that TPP plays another important role, which is protecting plants against abiotic and biotic stresses such as osmotic stress. In this study, the gene transcripts of first two enzymes in thiamine biosynthesis pathway, THIC and THI1/THI4 were identified and amplified from oil palm tissues. Primers were designed based on sequence comparison of the genes from Arabidopsis thaliana, Zea mays, Oryza sativa and Alnus glutinosa. Oil palm's responses in terms of the expression profiles of these two thiamine biosynthesis genes to an osmotic stress inducer, polyethylene glycol (PEG) were examined. The level of gene transcripts was analyzed using reverse transcriptase polymerase chain reaction (RT-PCR) and both THIC and THI1/THI4 gene transcripts were successfully amplified. The levels of transcription were measured and the results showed that the expression of THIC gene transcripts showed an increase of up to 200% in 1% PEG treated plant as compared to non-treated plant while the expression of THI1/THI4 gene transcripts showed an increase of up to 100% in treated plant as compared to non-treated plant. However, increase in concentration of PEG showed decrease in amount of transcription level for both gene transcripts. The results support the suggestion that thiamine may play an important function in plant defense against stresses as these findings may lead to an overexpression of thiamine in general.

Basal stem rot (BSR) disease is the most devastating disease in oil palm which is caused by a fungal pathogen, Ganoderma boninense. However, to date, there is no reliable control for this disease. This study investigated the antifungal potential of seaweed extracts against G. boninense and screening of the compounds possessing this antifungal activity. Four seaweed species namely cfSargassum oligocystum, Caulerpa racemosa, Caulerpa racemosa var. lamouroxii and cfHalimeda macrophysa were collected from Teluk Kemang, Port Dickson, Malaysia and their antifungal potential against G. boninense were evaluated. Two solvents with different polarities were used for crude extraction namely methanol and chloroform. Antifungal assay using crude methanolic and chloroform extracts from these seaweed species were carried out at various concentrations using the poisoned food technique. Caulerpa racemosa var. lamouroxii chloroform extract showed strong antifungal activity against G. boninense with 27.44% inhibition of the fungus followed by C. racemosa methanolic extract with 26.92% inhibition of the fungus at the lowest extract concentration of 0.25 mg/mL. The extracts were subjected to Gas Chromatography-Mass Spectrometry analysis and the dominant bioactive compounds detected in both extracts were phytol and l-(+)-ascorbic acid 2,6-dihexadecanoate which were also found in plant extracts showing antimicrobial activities in previous studies. The findings suggested that local Malaysian seaweed species have high potential as a source of antifungal compounds which could be useful specifically for the application in the oil palm industry.

Basal stem rot (BSR) is a disease in oil palm caused by a fungal pathogen, Ganoderma boninense. Utilisation of seaweeds as a control agent has not been explored. This study investigated the anti-fungal potential of Malaysian seaweed extracts against G. boninense and identification of the compounds. Seaweeds cf Sargassum oligocystum, Caulerpa racemosa, Caulerpa racemosa var. lamouroxii and cf Halimeda macrophysa were collected and subjected to crude extraction with various solvents. Methanolic extracts of all species displayed the highest yield with an average of 15.25% compared to dry weight. Anti-fungal assays were carried out against G. boninense using the poisoned food technique and three highest inhibitions were exhibited by C. racemosa var. lamouroxii dichloromethane extract (46.82%), cf H. macrophysa dichloromethane extract (33.49%) and C. racemosa methanol extract (28.06%). Dominant compounds detected via gas chromatography-mass chromatography (GC-MS) in extracts with anti fungal potential includes phytol. Anti-fungal assay using standard phytol showed growth inhibition of G. boninense of up to 21% inhibition. Caulerpa racemosa var. lamouroxii, cf H. macrophysa, C. racemosa and cf S. oligocystum dichloromethane extracts contain 474, 117, 106 and 19 mg litre-1 of phytol respectively. These findings suggested that Malaysian seaweeds are a good source of anti-fungal compounds for utilisation in controlling the BSR disease of oil palm in Malaysia.