Ligninolytic enzymes profiling in association with the aggressiveness of Ganoderma boninense isolates

Aims@#This study was designed to examine the enzyme activity of selected virulent isolates of Ganoderma boninense against oil palm. In a separate in vitro assessment, the effect of macronutrients on the mycelial growth of four selected Ganoderma spp. was also tested.@*Methodology and results@#The study involved a comparison of ligninolytic enzymes; lignin peroxidase (LiP), manganese peroxidase (MnP) and laccase (Lac) profiling of eight isolates of G. boninense, categorized into three levels of aggressiveness, with two control isolates (G. boninense PER71 and G. tornatum NPG1) using solid-state fermentation (SSF). The Principal Component Analysis (PCA) revealed that the isolates had a significant production of ligninolytic enzymes on day 80. The most aggressive isolate, ET61 had the highest Lac production. As for the macronutrient test, mycelial growth for all the Ganoderma spp. was highly affected by potassium (K).@*Conclusion, significance and impact of study@#The findings of this study elucidated the characteristics of G. boninense in relation to enzyme production for the degradation of oil palm lignin and the identification of essential nutrients involved in the survival and growth of Ganoderma spp. The study provides vital information on the pathogenic characteristics of G. boninense isolates involved in biomass degradation along with the role of nutrient on the growth of Ganoderma spp. that may influence basal stem rot (BSR) management in the field.

A potential mating-type biomarker to detect pathogenic Ganoderma species

Aims@#The basal stem rot disease in oil palm is caused by the pathogenic Ganoderma boninense, which is infectious after mating and forming dikaryotic hyphae. This study was aimed to generate a mating-type biomarker for the detection of pathogenic Ganoderma species.@*Methodology and results@#Mating-type region of Ganoderma was amplified using polymerase chain reaction (PCR) and primers flanking the mating-type region of other basidiomycetes. Amplified fragments were sequenced and were identified as the Ganoderma pheromone receptor gene of matB locus called the gprb2 gene. Using this biomarker, the pheromone receptor gene was detected in a total of 107 pathogenic Ganoderma spp. while the gene was not detected in the non-pathogenic Ganoderma lucidum. Phylogenetic tree analyses of the gene fragment encoding the partial amino acid sequence of gprb2 showed clades of close evolutionary relationship among the 107 pathogenic Ganoderma spp. Phylogenetic analyses using deduced amino acid sequences of the Ganoderma pheromone receptor b2 gene, gprb2 with homologous pheromone receptors of other basidiomycetous fungi revealed high conservation of this pheromone receptor within their respective taxonomy.@*Conclusion, significance and impact of study@#A potential mating-type biomarker was successfully identified that could detect pathogenic Ganoderma spp. The research findings will be helpful in oil palm screening to detect pathogenic Ganoderma spp. and gain further insight into the role of the mating-type loci of Ganoderma towards its pathogenesis in causing the basal stem rot disease of oil palm.

Evaluation on the effectiveness of combination of biocontrol agents in managing Ganoderma boninense of oil palm

Aims@#The development of an effective biocontrol formulation for inhibition of Ganoderma boninense, a well-known destructive pathogen in oil palm plantation is important to prolong the palm’s lifespan and reduce the losses due to this disease. In this paper, we present some new bioformulations with combination of different types of biocontrol agents in managing basal stem rot (BSR) disease. @*Methodology@#The effectiveness of the treatments designed as T1 (Trichoderma harzianum + Lecanicillium spp. + Streptomyces sundarbansensis + Pseudomonas aeruginosa), T2 (Penicillium simplicissimum + Lecanicillium sp. + S. sundarbansensis + P. aeruginosa), T3 (P. simplicissimum + P. aeruginosa) and T4 (LEStani®) was evaluated through treatment on the oil palm seedlings artificial infected by G. boninense and the results were expressed in disease severity index (DSI), bole severity index (BSI) and ergosterol content.@*Conclusion, significance and impact of study@#All tested treatments (T1-T4) managed to control the severity of the Ganoderma infection from continuously increasing when the treatments were applied either one month before or after artificial inoculation. The disease severity of infected seedlings without treatments had increased for almost 2-fold at the end of the trial. Moreover, T1 had the greatest inhibition of G. boninense with the lowest ergosterol content (a bioindicator of Ganoderma colonization) detected (676.67 g/mL), which is about 1.9-fold lower than control (1273.33 ug/mL) without treatments and a BSI score of 1. Based on the effectiveness among the four tested biocontrol formulations, T1 is the most promising formulation to be further evaluated in the field for control of BSR disease. However, more research is needed in the future to estimate the effective amount for application in open environment.

Anti-fungal substances of Bacillus subtilis against Ganoderma boninense

Aims@#To determine the optimum culture incubation time for β-glucanase and chitinase production by Bacillus subtilis as well as optimum pH and temperature condition for enzymatic activity against Ganoderma boninense. The suitable solvent (methanol, ethyl acetate or hexane) for the extraction of bacterial metabolites from B. subtilis were also determined. @*Methodology and results@#In vitro antagonistic activity of antifungal metabolites derived from B. subtilis to inhibit the growth of G. boninense was evaluated based on time of culture incubation, extraction solvent of the metabolites, and enzymatic treatments conditions including pH and temperature. The results showed that β-glucanase could be optimally produced (with a specific activity 4.222 U/mg-protein) after 28 h of incubation. The optimum pH and temperature for the activity of β-glucanase were 7.5 and 45 °C respectively when 1% laminarin used as the substrate. B. subtilis showed optimum chitinase activity (0.0514 U/mL) after 8 h of incubation. Optimum pH and temperature of chitinase were at pH 6.0 and 40 °C, respectively using 1% colloidal chitin as the substrate. β-glucanase crude enzyme showed strongest antifungal activities against the mycelial growth of G. boninense better than crude enzyme of chitinase with an inhibition rate of 47.75% at 5 days of incubation. Furthermore, cultivation of B. subtilis over 48 h produced antifungal metabolites which could inhibit the growth of G. boninense the most. The best solvent to extract metabolite from B. subtilis was identified as ethyl acetate that rendered an inhibition value of 38.91%. @*Conclusion, significance and impact of study@#Bacillus subtilis could be a potential biological control agent against G. boninense.

Preliminary screening and characterization of fungi isolated from forest soil as biocontrol agent against Ganoderma boninense

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.

Isolation of antagonistic Trichoderma spp. against selected phytopathogenic fungi from the field soils in Kelantan

Aims: Trichoderma is a soil borne mycoparasitic fungus which comprises a number of fungal strains that act as biocontrol agent. In this present study have investigated the diversity of Trichoderma in different cultivated soils in state of Kelantan. The effectiveness of biocontrol agent of isolated Trichoderm species was evaluated against the phytopathogen of Pyricularia oryzae, Fusarium oxysporum, and Ganoderma boninense. Methodology and results: The identification experiment was carried out on the basis of morphological characteristics as colony appearance, shapes and size of conidia, the branching patterns of conidiophores and phialides. Then, the effectiveness of biocontrol agent of Trichoderma species against the pathogens was tested in plate assay experiment. A total of 11 isolates were obtained from three different cultivated soils from Jeli (J), Machang (M) and Pasirmas (P). Morphological studies data identified as two groups of Trichoderma species as Trichoderma harzianum, and T. koningii. All the isolates showed the antagonistic activity against the pathogens while T. harzianum strain THMPA1 showed highest antagonistic activity of 80.00% against P. oryzae and in T. koningii strain TKMPA3 group showed highest antagonistic activity of 69% against P. oryzae. Conclusion, significance and impact of study: Among the 11 isolates of Trichoderma, the species of T. harzianum strain THMPA1 was the best as biocontrol agent against P. oryzae. Thus, diversity of Trichoderma species study is important to find promising species isolation of Trichoderma species which will be influenced in future to sustainable crop production and maintain green environment.