Use of Chitinolytic Bacteria as Biological Control of Colletotrichum capsici on Chili PlantsColletotrichum capsici is known as the causal agent of anthracnose disease in chili plant and may cause reduction of crop yield. Chitinolytic bacteria, namely Serratia marcescens KAHN 15.12, Bacillus thuringiensis SAHA 12.12, and BAE 36 were reported to have antagonistic activity against C. capsici. Therefore, a study was conducted to determine the potential of chitinolytic bacteria on controlling C. capsici on chili plants in greenhouse experiment. Three bacterial isolates used as biocontrol agent was formulated by using talcum as carrier materials. The methodologies consisted of characterization of bacterial isolates, formulation of biocontrol agent, viability test of bacterial isolate, efficacy of biocontrol agents in the laboratory and in the greenhouse. Disease severity in the laboratory reached 64% when chili treated with isolate formulation of BAE 36. In the greenhouse, BAE 36 isolate formulation and consortium formulation were able to suppress infection of C. capsici; each was indicated by disease incidence of 25% and 50%, respectively. These results indicated that chitinolytic bacterial formulations could be potencial as biocontrol agents of C. capsici.
The aim of this experiment was to characterize A. versicolor 3a1 α-amylase produced on cassava liquid waste media. Two types of media, base and combination media, were used as a comparison. Cassava liquid waste media contains 1% cassava starch, 1% yeast extract, 0.13% KH2PO4, and 0.05% MgSO4 diluted in cassava liquid waste. Base media contains same composition but using aquadest as a solvent, and combination media using mixture of aquadest and cassava liquid waste. A. versicolor 3a1 α-amylase showed its maximum specific activity in cassava liquid waste, base, and combination media after 3, 7, and 4 days incubation, respectively. Crude extract of α-amylase fromA. versicolor 3a1 was precipitated in 20-80% (w/v) ammonium sulphate. Precipitation of A. versicolor 3a1 α-amylase with 70% (w/v) ammonium sulphate on cassava liquidwaste, 60% on base media, and 60% on combination media will increase its specific activity 16.6, 4.28, and 5.65 times, respectively, compared to the specific activities ofcrude before precipitation. α-Amylase crude extract from A. versicolor 3a1 from all media showed its highest specific activity at 70oC and pH 5.0, and addition of FeSO4 increased the specific activity. Precipitated A. versicolor 3a1 α-amylase from all media showed its highest specific activity at 70oC and pH 6.0. Addition of FeSO4 precipitated 3a1 α-amylase from base and combination media will increase its specific activity, while MgSO4 will increase its specific activity in cassava liquid waste media. Thermostability assay revealed that the crude and the precipitated 3a1 α-amylase were relatively stable at 70oC up to 180 minutes incubation, except for precipitated3a1 -amylase on cassava waste media. Crude α-amylase 3a1 was relatively stable at pH 5-9 up to 1 hour incubation with wide pH ranges, while the precipitated with narrow pH ranges.
Fusarium spp. merupakan penyebab penyakit pada beberapa jenis tanaman salah satunya bawang merah sehingga dapat menurunkan produktivitas tanaman bawang merah (Allium cepa L.). Bakteri kitinolitik diketahui memiliki sifat antagonis terhadap Fusarium spp. Penelitian bertujuan mengetahui kemampuan isolat bakteri ABP5.1, ABP5.2.2, ABS4.1.2, BBP5.2.2 yang berasal dari pertanian bawang merah dalam menghambat pertumbuhan F. proliferatum. Sebanyak empat isolat bakteri terpilih hasil isolasi dari penelitian sebelumnya diuji kemampuannya dalam menghambat pertumbuhan Fusarium proliferatum. Tahapan penelitian terdiri atas karakterisasi isolat, uji aktivitas kitinolitik, uji antagonis antar isolat bakteri, dan uji antagonis isolat bakteri terhadap cendawan Fusarium proliferatum. Keempat isolat bakteri ABP5.1, ABP5.2.2, ABS4.1.2, dan BBP5.2.1 merupakan bakteri gram negatif. Uji kualitatif kitinolitik menunjukkan keempat isolat menghasilkan zona bening dengan indeks kitinolitik antara 0,04-1,0. Isolat bakteri ABS4.1.2 memiliki nilai indeks kitinolitik terbesar yaitu 1,09. Uji antagonis antar isolat bakteri menunjukkan hasil keempat isolat bakteri tidak bersifat saling antagonis. Uji antagonis bakteri terhadap cendawan Fusarium proliferatum dengan metode dual culture menunjukkan bahwa sebanyak dua dari empat isolat mampu menghambat pertumbuhan cendawan F.proliferatum. Isolat ABP5.2.2 memiliki daya hambat terbesar yaitu 41%, sedangkan isolat ABS4.1.2 memiliki daya hambat sebesar 40%.
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