Potential of rhizosphere fungi for biocontrol of vascular streak dieback in cocoa plants (<i>Theobroma cacao</i>)

Abstract. Ratnawati, Sudewi S, Jaya K, Sulistiawati. 2026. Potential of rhizosphere fungi for biocontrol of vascular streak dieback in cocoa plants (Theobroma cacao). Asian J Agric 10 (2): g100218. https://doi.org/10.13057/asianjagric/g100218. Pathogenic fungi are one of the main causes of the emergence of Vascular Streak Dieback (VSD) disease which can reduce the productivity of cocoa plants. This study aimed to evaluate the potential of rhizosphere fungi as biological control agents against VSD in cocoa plants through isolation, morphological identification, and in vitro antagonistic assays against Ceratobasidium theobromae. The results showed that a total of four rhizosphere fungal isolates from 20 isolates were successfully isolated from 5 cocoa plantation areas of Sidondo Village, Central Sulawesi, Indonesia. These isolates were identified as, isolates SA03 (Gliocladium sp.), SA05 (Aspergillus niger mf. 1), SA07 (A. niger mf. 2) and SA01 (Trichoderma sp.). Based on the dual culture test, the percentage of inhibition was 77.96% for SA01, 78.52% for SA07, 79.07% for SA05, and 80.19% for SA03. Microscopic observations revealed competition for space, namely mycoparasitism. Isolate SA07 showed the highest inhibitory power of 22.22%, followed by SA01 (20.44%), SA03 (11.55%), and SA05 (7.44%). The highest inhibitory power of SA07 may be due to the presence of volatile compounds which plays antibiosis. This finding highlights the discovery of the A. niger mf.2 (SA07) isolate which has the potential to produce effective volatile compounds and has the opportunity to be developed as an environmentally friendly biofumigant agent for VSD control. Further research is recommended to conduct molecular identification, effectiveness testing on a greenhouse scale, and chemical characterization of the volatile compounds produced.