ABSTRACT
Aims@#Erwinia psidii was first reported in 2017 to be the causal pathogen of papaya dieback disease (PDD) in Sabah, Malaysia. The present study aimed to isolate potential biocontrol agents against this pathogen. @*Methodology and results@#Out of the 20 samples collected from Crocker Range of Sabah, 154 bacteria and 55 fungi isolates were isolated and screened for their antagonistic activity against E. psidii. The fungi and bacteria which gave the highest inhibition to E. psidii were identified using molecular technique as Alcaligenes faecalis and Lecanicillium sp., respectively. Both isolates were selected for extraction of their secondary metabolites to determine their bioactivity against E. psidii. Micro-well dilution method was used to determine minimum inhibitory concentration (MIC) for each microbes’ extract. GC-MS analysis was carried out to determine their secondary metabolites. @*Conclusion, significance and impact of study@#Lecanicillium sp. (Diethyl ether, chloroform and ethyl acetate) extracts and A. faecalis (Diethyl ether extract) showed positive inhibition against E. psidii. GC-MS analysis revealed that both A. faecalis and Lecanicillium sp. had secreted some secondary metabolites such as N-formylmaleamic acid, Oleamide and D-1-Piperideine-2-carboxylic acid that may relate to the growth inhibition. Alcaligenes faecalis and Lecanicillium sp. are potential to be further investigated as biocontrol against E. psidii.
ABSTRACT
Aims@#The objective of this study is to investigate the potential of fungi isolated from forest soil as biocontrol against Ganoderma boninense, the causal pathogen of basal stem rot disease in Elaeis guineensis Jacq. (oil palm). @*Methodology and results@#Total 195 isolates were isolated from 20 soil samples collected from Crocker Range of Sabah and 54 fungal isolates were identified with 14 of them showed Percentage Inhibition of Radial Growth (PIRG) greater than 50%. A potential fungi (F15) with PIRG of 84.85% was later identified as Penicillium simplicissimum using molecular technique. Microscopy examination on P. simplicissimum and G. boninense interaction showed the evidence on the damage of pathogen hyphae when challenged by P. simplicissimum. The secondary metabolites of P. simplicissimum which may possibly contribute to this observation were later extracted using hexane, ethyl acetate and acetone and the extracts were tested in agar dilution bioassay (0.2 mg/mL to 1.0 mg/mL) against the pathogen. Ethyl acetate extract gave the highest inhibition to G. boninense (14.12 % in 0.4 mg/mL of ethyl acetate extract). @*Conclusion, significance and impact of study@#This is the first report, on the bioactivity of P. simplicissimum isolated from Crocker Range of Sabah against Ganoderma boninense, the causal pathogen of basal stem rot disease. Overall, our results indicated that P. simplicissimum has the potential to be further investigated as a biocontrol agent against G. boninense.
ABSTRACT
Aims: The outbreak of papaya dieback disease in Malaysia has been reported since 2003. Several reports previously confirmed Erwinia papayae and E. mallotivora to be the causal pathogen of the disease. The present study aimed to identify the causal pathogen of papaya dieback disease in Sabah. Methodology and results: Infected tissues of papaya dieback disease were collected from Kota Belud, Sabah and the bacterium responsible for the infection was isolated on Luria Bertani (LB) agar and nutrient agar (NA). Seven isolates with similar characteristics to Erwinia were isolated, subjected to the Koch’s Postulates test and then identified using 16S rRNA sequencing technique. The bacterium was identified to be E. psidii, a common pathogen to guava but not to papaya. Conclusion, significance and Impact of study: This report serves as the first confirmation of the E. psidii in causing papaya dieback disease, suggesting the possibility of this bacterium undergoing host shifting to papaya plants and the possibility of becoming another major threat to the papaya industry in the future.