Judul: Efektivitas Streptomyces spp. sebagai Agensia Hayati Mikrob Patogen pada Tanaman Cabai Besar (Capsicum annuum)
Abstrak: Pepper is one of important horticulture plants but it’s productivity has decreased, due to microbial pathogens. Streptomyces spp. indigenous isolates have been reported to have capability to produce antimicrobial compounds. This research aimed to assess the ability of Streptomyces spp. LSW05 and PS4-16, two potential isolates based on previous in vitro assay, in controlling microbial pathogens, particularly Cercospora sp., in pepper plant in a field trial and to obtain an effective application method. The two isolates were applied singly or in combination using three methods (seed coating, soil drenching, and plant spraying). Streptomyces treatment significantly supressed disease severity and increased plant height and fruit production. Soil drenching with combination of the two isolates was the best treatment to suppress disease with the value of area under the disease progress curve (AUDPC) was only 234 with relative control effectiveness up to 81%. Plant sprayed with combination of the two isolates produced the highest fruits number (697 g/plot). Seed coated with PS4-16 isolate was the best treatment to increase plant height with the value of area under the height progress curve (AUHPC) was 1350, which was 27% higher than the non-treated plants. Seed coating with the combined isolates increased plant dry weight by 143%. Cost analysis showed that seed coating with the two isolates gave the highest profit as high as Rp 9.869.600 with relative control effectiveness up to 43%.
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Judul: Perlakuan Benih Cabai (Capsicum annuum L.) dengan Rizobakteri secara Tunggal ataupun Kombinasi untuk Mengendalikan Phytophthora capsici dan Meningkatkan Pertumbuhan Tanaman.
Abstrak: Seed treatment of hot pepper using rhizobacteria is an alternative to fungicide in controlling phytophthora blight disease that caused by Phytophthora capsici fungus pathogen. The objectives of this research were to evaluate: (1) the effectiveness of rhizobacteria isolates in inhibiting P. capsici growth, and (2) the effect of seed treatment using rhizobacteria on seed vigor and plant growth, and incidence of phytophthora blight disease. This research consisted of three experiments, all experiments were arranged in completely randomized design using one factor. The first experiment (in vitro) consisted of nine levels i.e. seven combination isolates of rhizobacteria, metalaxyl and untreated control. The second experiment (on the seedbed) consisted of five levels of seed treatments i.e. ST116B rhizobacteria, CM8 rhizobacteria, ST116B + CM8 rhizobacteria, metalaxyl and control. The third experiment (in the green house) consisted of six levels of seed treatments i.e. ST116B rhizobacteria, CM8 rhizobacteria, ST116B + CM8 rhizobacteria, metalaxyl, positive and negative control. Results of in vitro experiment showed that all rhizobacteria, single or combinations, were able to inhibit P. capsici growth. The highest inhibitions were shown by CM8, ST116B, and ST116B + CM8 consequtively. Seed treatments of hot pepper using ST116B, CM8 and ST116B + CM8 rhizobacteria did not increase seed vigor but increased the number of leaves 6 weeks after transplanting, and reduced the incidence of phytophthora blight disease. There were no significant differences whether the rhizobacteria was applied singly or in combination of the two isolates. Rhizobacteria ST116B is suggested to be used in hot pepper seed treatment before planting.
Keyword: biological agents, metalaxyl, phytophthora blight disease, rhizobacteria isolates

Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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