Judul: Pengaruh Suhu, pH, dan Konsentrasi terhadap Senyawa Bioaktif Antifungi Ralstonia pickettii dalam Menekan Pertumbuhan Rhizoctonia solani
Abstrak: Rice sheath blight disease, caused by Rhizoctonia solani is an important disease on rice and loss of harvest up to 30%. Ralstonia pickettii was one of the biological agent from the group of bacteria which was able to suppress the growth of R. solani. In the laboratory scale, a filtrate of R. pickettii antifungal bioactive compound was able to suppress the growth of fungi up to 100%. Temperature and pH were the factors which were expected to influence the bioactive compound activity. The concentration of this antifungal bioactive filtrate also influenced the growth of R. solani inhibition. Therefore, this research was aimed to know the effectiveness of temperature, pH and concentration of R. pickettii to suppress the growth of R. solani. This research used factorial randomize complete design (RAL) which temperature: 25oC, 30oC and 40oC as the first factor and pH: 5, 6, 7, 8, and 9, were the second factor in three times of repetition. The result of this research showed that at temperature of 25oC and 35oC, antifungal bioactive compound were effective to suppress R. solani activity and pH did not show significant effect to bioactive compound activity. The concentration of 7.5 and 10 % was able to suppress R solani with 40% of the inhibition value.
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Judul: The potency of antifungal bioactive compound producing bacteria to control rice sheath blight disease
Abstrak: The objectives of this research were to (i) screen some potential bacteria as biological control agents of the sheath blight disease caused by R. solani, (ii) identify character of the selected bacteria strains as biological control agents, and (iii) characterize the antifungal activities of the antifungal bioactive compound produced by the selected strains against R. solani. The antagonist bacteria were isolated from rhizospheric soil, rice plant, and pond water collected from several locations. Screening of bacteria strains on the growth inhibition of R. solani was conducted in the laboratory, while the selection of bacteria for their effectiveness to suppress sheath blight disease were done in the screen house. The result of this research showed that there are three bacterial isolates which antifungal activity significantly suppressed the rice sheath blight disease, i.e. TT47, SS19, and BR2 with suppression ability of 79,6, 56,4, and 49,47%, respectively. Molecular analysis of partial sequence of 16S rRNA showed that SS19, TT47, and BR2 isolates were Serratia marcescens, Ralstonia pickettii, and Bacillus subtilis, respectively. These biocontrol agents are not phythotoxic, produce siderophore, and phosphate-solubilizing. S. marcescens SS19 and R. pickettii TT47 were chitin-degrading bacteria but B. subtilis BR2 was not. The filtrate from fermentation broth of the R. pickettii TT47 and B. subtilis BR2 inhibited the growth of R. solani. The antifungal bioactive compound was relatively stable on pH range from acidic to basic (pH 4, pH 7, and pH 10). The optimum activity of antifungal bioactive compound was at room temperature (25-27 0C) and tend to decrease at higher temperature (60, 80. 100, and 121 0 Key words: The rice sheath blight, antifungal bioactive compounds, Serratia marcescens, Ralstonia pickettii, Bacillus subtilis. C). The antifungal activity of hexane extract of R. pickettii TT47 and ethyl acetate extract of B. subtilis BR2 in vitro revealed significant growth inhibition to R. solani, respectively by 86,3% and 77,8%. MIC of hexane extract and ethyl acetate extract were 0,1 mg/l and 10 mg/l respectively, and both extracts are not phythotoxic against the rice seedling.
Keyword: Bacillus subtilis, Rhizoctonia solani Kühn, Plant diseases

Judul: Embriogenesis ikan buta (Astyanax fasciatus)
Abstrak: Ikan buta Astyanax fasciatus adalah spesies ikan unik dari famili Characidae yang menempati perairan dalam gua di Wilayah La Cueva Chica-San Luis Potasi-Mexico. Ikan ini memiliki mata yang tereduksi (Blind Cavefish) dan warna kulit merah muda, pucat serta mengkilap.
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