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A study was carried out to screen 25 Actinomycetes isolates that have ability to act as biocontrol agents Actinomycetes against Ganoderma sp. TB3 and Ganoderma sp. TB4. Among 25 Actinomycetes isolates, only Actinomycetes SM12 can inhibit the growth of both Ganoderma sp. TB3 (52 %) and Ganoderma sp. TB4 (60 %). Antagonistic assay using cross streak method with a longer period of delayed antagonism showed higher inhibition effect to the growth of Ganoderma sp. TB3 (76 %) and Ganoderma sp. TB4 (85 %). Identification of Actinomycetes SM12 based on 16S rRNA revealed that Actinomycetes SM12 belong to Streptomyces cellulosae. The Actinomycetes SM12 isolate produces rectinaculum-apertum spore chain and forms a colony that exhibited white to greyish color. Enzyme activity test showed that the cultures are positive in amylase, protease, lipase and cellulase production respectively.

Bacillus spp. are known as potential bacteria as biocontrol agent against fungal phytopathogen, such as Aspergillus niger. The Aspergillus niger can cause many problems, including in agriculture sector. Antagonist activity of 3 bacteria isolates Bacillus sp. KRG, KRT and LDR have been carried out against Aspergillus niger CP. Dual culture method for antagonist assay was performed using streak, disc, and pour plate technique. Result from the disc technique showed that there is no significant antagonist activity differences between all isolates KRG, KRT, and LDR (51.94 %, 61.24 %, and 54.53 %). The highest inhibition effect was shown clearly in pour plate technique with inhibition value almost 100 %. The LDR isolate was selected for further evaluation based on the physicochemical characters according to strong catalase activity and rapid fermentation. Antibiosis assay was performed in order to evaluate the antifungal compound produced by LDR isolate using agar and broth culture method. The filtrates from growth medium 7, 10 and 12 days fermentation were used for antibiosis assay against Asp. niger CP. The growth of Asp. niger CP was inhibited by 10- and 12-days filtrate fermentation in all the 2 methods used. The percentage of inhibition of isolates observed in agar culture were 84.41 % and 84.21 %. Biomass of Asp. niger CP reduced by 74.55 % and 85.54 %.

Marine actinomycetes are being explored to discover potential actinomycetes that produce antifungal compounds. In a previous study, marine actinomycetes isolates from the mangrove ecosystem were found to inhibit growth of the phytopathogenic fungi Colletotrichum siamense KA. In this study, the three of these isolates with the highest antagonistic activity—SM11, SM14, and SM15—were evaluated for their antifungal activity using antibiosis assay. The fermentation was performed in SCB:PDB medium (1:1) for 6, 9, and 12 days. The results showed that SM14 was the strongest potential isolate; it inhibited the growth of C. siamense KA on average up to 64.90% for 12 days on PDA filtrate medium. Molecular identification showed SM14 was closely related to Streptomyces sanyensis, but had differences in morphological and biochemical characteristics compared to SM11 or SM15. This indicated that the three isolates were different strains and may challenge further research on identifying and analyzing their antifungal compounds.

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Bacillus spp. was recognized as biocontrol agent because could produce antifungal towards many phytopathogenic fungi. In relation to study the potency of B. siamensis LDR as biocontrol, antagonistic activity of the bacilli was evaluated against Fusarium sp., Ganoderma sp., and Chaetomium globosum InaCC F228. The antagonist assay was carried out by dual culture method using streak and pour plate technique. Result of antagonistic activity assay with streak technique showed that growth inhibition rate of Fusarium sp., Ganoderma sp., and Chaetomium globosum InaCC F228 were 36.83%, 55.20%, and 33.78%, respectively. Antagonist assay using pour plate technique showed that percentage growth of inhibition for Fusarium sp. (93.96%), Ganoderma sp. (100%), and Chaetomium globosum InaCC F228 (76.64%) were higher than the results from streak method. Furthermore, results from antibiosis assay showed that growth inhibition rate of Fusarium sp., Ganoderma sp., and Chaetomium globosum InaCC F228 were 10.85%, 73.31%, and 30.32% respectively.

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