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 untuk Mengendalikan Phytophthora capsici, Meningkatkan Vigor Benih, dan Pertumbuhan Tanaman
Abstrak: Rhizobacteria seed treatment was an alternative way instead of using chemicals to combat plant disease. The objectives of this research were (1) to select rhizobacteria isolates which inhibiting Phytophthora capsici growth; and (2) to study the effect of seed treatment using rhizobacteria on P. capsici growth, seed vigor and plant growth of hot pepper. This research consisted of three experiments, all experiments were arranged in completely randomized design using one factor. The first experiment consisted of 24 levels of rhizobacteria i.e. 23 isolates of rhizobacteria and P. capsici isolate (control). The second experiment (on the seedbed) consisted of five levels of seed treatments i.e. ST116B rhizobacteria, ST156 rhizobacteria, E3 rhizobacteria, metalaxyl, and control. The third experiment (in the green house) consisted of six levels of seed treatments i.e. ST116B rhizobacteria, ST156 rhizobacteria, E3 rhizobacteria, metalaxyl, positive control, and negative control. Results of in vitro experiment showed that three of 23 isolates tested i.e. ST156, ST116B, and E3 obstructed P. capsici growth. Seed treatments using ST116B, ST156, and E3 rhizobacteria increased seed vigor (vigor index). The best seed treatment increasing plant growth (number of leaves) and potentially controlling phytophthora blight disease was using ST116B rhizobacteria
Keyword: phytophthora blight disease, metalaxyl, dual culture

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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