Distinct Detection of Ganoderma Boninense On Metal Oxides-Gold Nanoparticle Composite Deposited Interdigitated Electrode DNA sensor

Oil palms suffer severe losses due to Ganoderma boninense infection that causes Basal Stem Rot (BSR). The available detection measuring the severity of BSR disease have not proved satisfactory output. Due to the influence of oil palm industry in country’s economy, effective and efficient means of diagnostic measure is mandatory. Among the available diagnostic tools, biosensors were redeemed to yield the most rapid and selective results. To overcome the current issues, herein Interdigitated Electrode (IDE) electrochemical DNA biosensor to detect Ganoderma boninense was successfully designed and fabricated by thermal deposition. Lift-off photolithography fabrication process was applied followed by the surface chemical functionalization via seed deposition. Zinc Oxide (ZnO) and Titanium Dioxide (TiO2) were overlaid and the functionalized metal oxides IDE surfaces were used to detect DNA sequence complementation from Ganoderma boninense. Furthermore, gold nanoparticles were doped to increase the surface to volume ratio and enhance biocompatibility. Characterizations were made by validating the sensor’s topology characteristics and electrical characteristics. From the results recorded, it has been justified that IDE with ZnO doped with gold nanoparticles surface serves as an excellent DNA sensor for the detection of Ganoderma boninense with a remarkable current of 290 nA and 176 nA for immobilization and hybridization respectively.

Antagonistic capacity of dark septate endophytes (DSE) against Ganoderma boninense from oil palm (Elaeis guinensis Jacq.)

Ganoderma boninense, a causal agent of basal stem rot, as one of the major problems in oil palm plantation in Indonesia. The potential of dark septate endophytes (DSE) as biocontrol agents for G. boninense is not widely studied. Therefore, this study aims to screen DSE strains to obtain high antagonistic strains. The antagonistic capacity of 10 DSE strains was determined based on the growth inhibition in the dual culture, and volatile compounds challenge against G. boninense, in vitro. Volatile compound profiling of selected DSE strains that showed the highest challenge capacity was done using Pyrolysis Gas Chromatography-Mass Spectrometry. Among 10 DSE strains tested, TKC 2.2a had the highest percentage of G. boninense inhibition in dual cultures and the volatile compound challenge. This strain inhibited better if grown in media seven days earlier than grown simultaneously with G. boninsense. The volatile compounds of 14 days old TKC 2.2a were of 2H-1-Benzopyran-7-ol, 3,4-dihydro-5-methoxy-6-methyl-2-phenyl; 4-Allyl-2,6-dimetho-xyphenol; and hexa-decanoic acid, which were reported as having either antimicrobial or antifungal activities. These results indicate that DSE TKC 2.2a can be a candidate for a biocontrol agent against G. boninense in oil palm, depending on further research on its ability to reduce basal stem rot symptoms.

Macrofungal identification and species richness in Cigelung Landscape and its influence on the presence of oil palm pathogens in PTPN VIII

Dungus Iwul Nature Reserved (CADI) is a remnant patch of tropical rainforest converted into plantations with neither past data nor study in macrofungi. In this article, we explored and identified macrofungal fruitbody in CADI and PTPN VIII Oil Palm Plantation (PTPN) around the nature reserve. The inventory was carried out with the opportunistic sampling methods assisted by the line intercept. Morphological characteristics were used to identify the macrofungal fruitbodies species. We found that the species richness in the study area stood at 120, with 70 species found in CADI, 23 species in PTPN planted in 2003, and 57 species in PTPN planted in 2004. These 120 species consist of 76 genera, 41 families, 11 orders, and four classes in Subkingdom Dikarya. Schizophyllum commune and Marasmiellus candidus in CADI and S. commune in PTPN planted in 2003 and 2004 were the species found with the highest relative frequency. Neither sign of basal stem rot on oil palm trees nor Ganoderma fruitbodies were found in both PTPN study locations, even though the fruitbodies were found in CADI. Further research is needed to determine if nature reserve could be a barrier against pathogens of monoculture oil palm plantation in a similar landscape model.

Classification of Non-Infected and Infected with Basal Stem Rot Disease Using Thermal Images and Imbalanced Data Approach

Basal stem rot (BSR) disease occurs due to the most aggressive and threatening fungal attack of the oil palm plant known as Ganoderma boninense (G. boninense). BSR is a disease that has a significant impact on oil palm crops in Malaysia and Indonesia. Currently, the only sustainable strategy available is to extend the life of oil palm trees, as there is no effective treatment for BSR disease. This study used thermal imagery to identify the thermal features to classify non-infected and BSR-infected trees. The aims of this study were to (1) identify the potential temperature features and (2) examine the performance of machine learning (ML) classifiers (naïve Bayes (NB), multilayer perceptron (MLP), and random forest (RF) to classify oil palm trees that are non-infected and BSR-infected. The sample size consisted of 55 uninfected trees and 37 infected trees. We used the imbalance data approaches such as random undersampling (RUS), random oversampling (ROS) and synthetic minority oversampling (SMOTE) in these classifications due to the different sample sizes. The study found that the Tmax feature is the most beneficial temperature characteristic for classifying non-infected or infected BSR trees. Meanwhile, the ROS approach improves the curve region (AUC) and PRC results compared to a single approach. The result showed that the temperature feature Tmax and combination feature TmaxTmin had a higher correct classification for the G. boninense non-infected and infected oil palm trees for the ROS-RF and had a robust success rate, classifying correctly 87.10% for non-infected and 100% for infected by G. boninense. In terms of model performance using the most significant variables, Tmax, the ROS-RF model had an excellent receiver operating characteristics (ROC) curve region (AUC) of 0.921, and the precision–recall curve (PRC) region gave a value of 0.902. Therefore, it can be concluded that the ROS-RF, using the Tmax, can be used to predict BSR disease with relatively high accuracy.

Alterations in Mycelial Morphology and Flow Cytometry Assessment of Membrane Integrity of Ganoderma boninense Stressed by Phenolic Compounds

Global increase in demand for palm oil has caused an intensification in oil palm plantation; however, production is greatly hindered by Basal Stem Rot (BSR) disease caused by Ganoderma boninense. There are many approaches to controlling BSR, although, there is no accurate, sustainable and effective method to suppress G. boninense completely. Hence, four phenolic compounds [Gallic acid (GA), Thymol (THY), Propolis (PRO) and Carvacrol (CARV)] were selected to evaluate their antifungal effect, ability to alter the mycelium morphology, and fungal cell integrity against G. boninense. Significant differences (p < 0.05) were observed and 94% of inhibition was exerted by GA on G. boninense growth. Scanning Electron Microscopy and High-Resolution Transmission Electron Microscopy observations revealed that GA and THY treatment caused severe damage to the mycelium and recorded the highest amount of sugar and electrolyte leakage. The study of cell integrity and morphological disruption has elucidated the reduction of G. boninense cell viability. Generally, our findings confirm the fungistatic effects of GA and THY. The evolution of phenolic compounds during the phytopathology studies indicated their coherence in eradicating the G. boninense. It is proposed that GA and THY had the potential to be developed further as a natural antifungal treatment to suppress G. boninense.