Savina Melia and I Nyoman P. Aryantha
School of Life Science and Technology, Institut Teknologi Bandung
Jalan Ganesha 10 Bandung 40132 - INDONESIA
The antagonistic cosmopolitan fungi Trichoderma harzianum is well known for its ability to produce some active compounds, such as antibiotics that play a role in suppressing the growth of phytopathogenic fungi e.g. Fusarium oxysporum which causes the wilt disease in tomato plants. Optimization of the medium was made by adding the polysaccharide-group elicitor as chitosan to induce the biosynthesis of secondary metabolites such as antibiotics-antifungal. The addition of chitosan at low concentration (0.01%; 0.02%; and 0.03%) to the medium of T. harzianum was conducted to analyze its antifungal activity effect against the phytopathogenic fungi of tomato wilt disease, F. oxysporum, both in vitro and in vivo. This study includes : 1. Sub-culturing pure culture of T. harzianum and F. oxysporum, 2. Determination of the optimal incubation time, 3. Selection of chitosan concentration, 4. Fermentation of T. harzianum, 5. Extraction of T. harzianum with etil acetate and methanol, 6. In vitro inhibition assay of T. harzianum extract on the growth of F. oxysporum at 0.5%; 0.75%; 1%; 2.5%; and 5% concentration in PDA medium, 7. In vivo inhibition assay of T. harzianum extract on Fusarium wilt disease of tomato seedling at 1% and 2.5% concentration in soil medium. The result showed that in general the best incubation time for all three chitosan treatment was 84 hours for dynamic fermentation followed by static fermentation up to 168 hours. The minimum effective concentration of chitosan that produced the highest antifungal activity against F. oxysporum was 0.02% in PDB medium, which is used for the next step. The best in vitro assay result was shown in methanol-extracted T. harzianum with minimum effective concentration at 2.5% in PDA medium that effectively inhibit the growth of pathogen. Treatment of tomato seed soakage and soil drenched with 2.5% T. harzianum extract effectively suppressed the seedling death and decreased the appearance of Fusarium wilt disease. Chitosan addition in T. harzianum medium has increased the antifungal activity against F. oxysporum and could be considered as the alternative to develop biocontrol system of Fusarium wilt disease in tomato.
Key words : antifungal activity, chitosan, Trichoderma harzianum, Fusarium oxysporum
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