Judul: Efikasi Bakteri Endofit dan Plant Growth Promoting Rhizobacteria dalam Menekan Perkembangan Penyakit Layu Bakteri (Ralstonia solanacearum) pada Tomat
Abstrak: Tomato (Lycopersicum esculentum Mill.) is a popular vegetable in Indonesia, but the production levels are still fluctuated. One of the factors affected productivity is the incidence of bacterial wilt disease caused by Ralstonia solanacearum. Effective control to manage the disease which is environmentally friendly is the use of biocontrol agents. Application of endophytic bacterial (Staphylococcus epidermidis BC4) and Plant Growth Promoting Rizhobacteria (Pseudomonas fluorescens RH4003 and Bacillus subtilis AB89) as biocontrol of tomato bacterial wilt was expected to be an alternative tool. The objective of this study is to determine the efficacy of combination among endophytic bacteria and PGPR to suppress the development of bacterial wilt disease (R. solanacearum) and promote the growth of tomato. Depend on the growth test (growth rate and dry weight plant), the combination of bacteria that could promote the growth of tomato plant was combination of S. epidermidis BC4 75% with P.fluorescens RH4003 25%. That combination gave a better effect than the other treatments and control, but did not provide better suppression than treatment of single bacterium. Based on sinergism test, the relationship between PGPR and endophytic bacteria was an antagonistic. However, there were combination treatments which were able to suppress the disease, ie. combination of S. epidermidis BC4 50% with P. fluorescens RH4003 50% and the combination of S. epidermidis BC4 50% with B. subtilis AB89 50%.
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Judul: Keefektifan berbagai formulasi plant growth promoting Rhizobacteria (PGPR) dan Bakteri endofit terhadap penyakit layu bakteri yang disebabkan oleh ralstonia solanacearum pada tomat
Abstrak: Ralstonia solanacearum adalah penyebab penyakit layu bakteri yang paling serius pada tanaman Solanaceae. Berbagai pengendalian telah dilakukan tetapi patogen masih sulit dikendalikan. Aplikasi formulasi plant growth promoting rhizobacteria (PGPR) dan bakteri endofit diharapkan menjadi alternatif dalam mengendalikan penyakit layu bakteri. Penelitian ini bertujuan untuk mengevaluasi keefektifan berbagai formulasi PGPR dan bakteri endofit terhadap penyakit layu bakteri yang disebabkan oleh Ralstonia solanacearum pada tanaman tomat di lapangan. Formulasi biokontrol dilakukan dengan menyiram bibit tomat setelah pindah tanam. Bakteri PGPR yang digunakan pada penelitian adalah Bacillus subtilis AB89, diperoleh dari koleksi Laboratorium Bakteriologi Tumbuhan, Departemen Proteksi Tanaman, Fakultas Pertanian, Institut Pertanian Bogor. Bakteri endofit yang digunakan yaitu Staphylococcus epidermidis dengan kode isolat BC4. Formulasi yang digunakan sebagian mengandung carboxy methyl celullose (CMC) 1%. Berdasarkan nilai Area Under Disease Progress Curve (AUDPC), aplikasi formulasi bakteri PGPR dan bakteri endofit tidak berbeda nyata dibandingkan dengan kontrol. Berdasarkan index penekanan penyakit, perlakuan S. epidermidis secara tunggal (B0S100) memberikan penekanan yang paling baik terhadap penyakit layu bakteri. Index penekanan S. epidermidis secara tunggal (B0S100) sebesar 40.96%. Data AUDPC, bobot kering tajuk, bobot kering akar, dan bobot hasil panen buah menunjukkan bahwa perlakuan formulasi bakteri dengan penambahan CMC tidak berbeda nyata dibandingkan dengan perlakuan formulasi bakteri tanpa penambahan CMC.
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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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