Inhibition of Dark Septate Endophyte Fungus Metabolites Against Oil Palm Basal Stem Rot Disease Caused by Ganoderma boninense.

Abstract

The extensification of oil palm plantations in Indonesia has been accompanied by an increase in the occurrence of Basal Stem Rot (BSR) disease caused by Ganoderma boninense. Biological control is one of the alternative efforts to suppress G. boninense infection by the application of biological control agents such as Dark Septate Endophyte (DSE) fungus. This research aimed to assess the potential of three DSE fungi metabolites to control G. boninense in oil palm trees and to detect the active ingredients contained therein. The abilities of filtrates from three DSE fungi, i.e. Cladophialophora nyingchiensis S5.1, Exophiala pisciphila S1.4, and Diaporthe pandanicola TM.1.1 were evaluated in vitro for their suppression to G. boninense at concentrations of 0%, 15%, 30%, 45%, 60%, and 75% (v/v). Filtrates were also evaluated in vivo using oil palm seedlings with treatments consisting of positive and negative controls, once and/or twice applications of DSE filtrate with concentrations of 27% and 75%. At the end of the experiment, the seedlings were disassembled to evaluate the severity of internal symptoms. C. nyingchiensis S5.1 incubated in Potato Dextrose Broth (PDB) medium for two weeks produced most effective filtrate (code: S5.1) with IC55 value was the lowest, i.e. up to 43.78%. The filtrate of S5.1 at concentration of 75% caused the highest colony inhibition of G. boninense up to 88.63%. Twice applications with 75% of S5.1 filtrate significantly increase plant height and stem diameter. Filtrate isolate S5.1 contains metabolite compounds Linolein and 5- Oxoproline which can act as antifungals that play a role in inhibiting the growth of Ganoderma boninense.