Phenazine from Pseudomonas aeruginosa UPMP3 induced the host resistance in oil palm (Elaeis guineensis Jacq.)-Ganoderma boninense pathosystem.

Pseudomonas aeruginosa developed its biocontrol agent property through the production of antifungal derivatives, with the phenazine among them. In this study, the applications of crude phenazine synthesized by Pseudomonas aeruginosa UPMP3 and hexaconazole were comparatively evaluated for their effectiveness to suppress basal stem rot infection in artificially G. boninense-challenged oil palm seedlings. A glasshouse experiment under the randomized completely block design was set with the following treatments: non-inoculated seedlings, G. boninense inoculated seedlings, G. boninense inoculated seedlings with 1 mg/ml phenazine application, G. boninense inoculated seedlings with 2 mg/ml phenazine application and G. boninense inoculated seedlings with 0.048 mg/ml hexaconazole application. Seedlings were screened for disease parameters and plant vigour traits (plant height, plant fresh weight, root fresh, and dry weight, stem diameter, and total chlorophyll) at 1-to-4 month post-inoculation (mpi). The application of 2 mg/ml phenazine significantly reduced disease severity (DS) at 44% in comparison to fungicide application (DS = 67%). Plant vigour improved from 1 to 4 mpi and the rate of disease reduction in seedlings with phenazine application (2 mg/ml) was twofold greater than hexaconazole. At 4, 6 and 8 wpi, an up-regulation of chitinase and ß-1,3 glucanase genes in seedlings treated with phenazine suggests the involvement of induced resistance in G. boninense-oil palm pathosystem.

Utilization of magnesium-rich synthetic gypsum as magnesium fertilizer for oil palm grown on acidic soil.

A study was conducted to determine the impact of applying different sources of Mg, namely kieserite, ground magnesium limestone (GML) and Mg-rich synthetic gypsum (MRSG) on an acid tropical soil, oil palm growth and production. Besides high amount of Mg and Ca, MRSG contains S. Exchangeable Ca in the untreated soil of the plantation was 0.64 cmolc kg-1, but its critical level to sustain oil palm growth was 0.9 cmolc kg-1. MRSG was applied in the plantation as Mg-fertilizer; however, since Ca is also a limiting nutrient, oil palm growth was correlated (r = 0.69) with Ca supplied by the MRSG. Mg needed to sustain oil palm production is normally supplied by kieserite. Its requirement can be met at a lower cost compared to that of the kieserite by using MRSG. Due to MRSG treatment, exchangeable Ca in the soil increased steadily to satisfy the requirement of oil palm for fruit bunches production. From the glasshouse and field study, it was observed that MRSG applied at 1.5 times the recommended rate gave results comparable to that of the kieserite. MRSG treatment resulted in the increase of soil pH to >5 that precipitated Al3+ as inert Al-hydroxides, which eventually enhanced oil palm seedlings growth. Thus, MRSG can also replace GML to increase soil pH and satisfy the Ca and Mg requirement of oil palm. It can be concluded that MRSG has the potential to be used as a source of Mg as well as Ca for oil palm grown on acidic soil.

Application of arbuscular mycorrhizal fungi with Pseudomonas aeruginosa UPMP3 reduces the development of Ganoderma basal stem rot disease in oil palm seedlings.

The effect of arbuscular mycorrhizal fungi (AMF) in combination with endophytic bacteria (EB) in reducing development of basal stem rot (BSR) disease in oil palm (Elaeis guineensis) was investigated. BSR caused by Ganoderma boninense leads to devastating economic loss and the oil palm industry is struggling to control the disease. The application of two AMF with two EB as biocontrol agents was assessed in the nursery and subsequently, repeated in the field using bait seedlings. Seedlings pre-inoculated with a combination of Glomus intraradices UT126, Glomus clarum BR152B and Pseudomonas aeruginosa UPMP3 significantly reduced disease development measured as the area under disease progression curve (AUDPC) and the epidemic rate (R L) of disease in the nursery. A 20-month field trial using similar treatments evaluated disease development in bait seedlings based on the rotting area/advancement assessed in cross-sections of the seedling base. Data show that application of Glomus intraradices UT126 singly reduced disease development of BSR, but that combination of the two AMF with P. aeruginosa UPMP3 significantly improved biocontrol efficacy in both nursery and fields reducing BSR disease to 57 and 80%, respectively. The successful use of bait seedlings in the natural environment to study BSR development represents a promising alternative to nursery trial testing in the field with shorter temporal assessment.

Is plasma beta-glucuronidase a novel human biomarker for monitoring anticholinesterase pesticides exposure? A Malaysian experience.

A cross-sectional study was conducted to investigate the effects of acute and chronic pesticide exposure on the plasma beta-glucuronidase enzyme activity among five patients of acute pesticide poisoning in Tengku Ampuan Rahimah Hospital, Klang, 230 farmers in the MADA area, Kedah and 49 fishermen in Setiu, Terengganu. The duration of pesticide exposure among the patients was unknown, but the plasma samples from patients were collected on day one in the hospital. The duration of pesticide exposure among the farmers was between 1 and 45 years. The beta-glucuronidase activity was compared with plasma cholinesterase activity in the same individual. The plasma cholinesterase activity was measured using Cholinesterase (PTC) Reagent set kit (Teco Diagnostics, UK) based on colorimetric method, while the plasma beta-glucuronidase activity was measured fluorometrically based on beta-glucuronidase assay. The plasma cholinesterase activity was significantly reduced (p<0.05) among the patients (1386.786+/-791.291 U/L/min) but the inhibition in plasma cholinesterase activity among the farmers (7346.5+/-1860.786 U/L/min) was not significant (p>0.05). The plasma beta-glucuronidase activity among the farmers was significantly elevated (p<0.05) (0.737+/-0.425 microM/h) but not significant among the patients (p>0.05). The plasma cholinesterase activity was positively correlated with the plasma beta-glucuronidase activity among the farmers (r=0.205, p<0.01) but not among the patients (r=0.79, p>0.05). Thus, plasma beta-glucuronidase enzyme activity can be measured as a biomarker for the chronic exposure of pesticide. However, further studies need to be performed to confirm whether plasma beta-glucuronidase can be a sensitive biomarker for anticholinesterase pesticide poisoning.