Judul: Keefektifan bakteri endofit dan plant growth promoting rhizobacteria dalam menekan penyakit layu bakteri (Ralstonia solanacearum) pada tomat
Abstrak: Penyakit layu bakteri merupakan salah satu penyakit penting pada tanaman tomat. Penyakit ini disebabkan oleh bakteri patogen Ralstonia solanacearum. Kisaran inang dari R. solanacearum sangat luas. Penelitian ini bertujuan untuk mengetahui keefektifan bakteri endofit jika dikombinasikan dengan bakteri PGPR dalam menekan penyakit layu bakteri pada tomat secara in planta di rumah kaca dan di lapangan serta mengetahui pengaruhnya terhadap pemacuan pertambahan tinggi tanaman. Metode penelitian yang dilakukan yaitu dengan menyiram bibit tomat dengan agens biokontrol yang dilakukan sebelum pindah tanam dan media tanam yang digunakan mengandung R. solanacearum. Bakteri endofit yang digunakan berasal dari penelitian sebelumnya yaitu isolat dengan kode BL10, BC4, dan BC10. Bakteri PGPR yang digunakan merupakan koleksi Laboratorium Bakteriologi Tumbuhan, Departemen Proteksi Tanaman, IPB yaitu P. fluorescens RH4003 dan B. subtilis AB89. Perlakuan yang diberikan terdiri dari 12 perlakuan yaitu aplikasi dari masing-masing bakteri endofit, masing-masing bakteri PGPR, dan kombinasi keduanya serta kontrol. Rancangan percobaan yang digunakan yaitu Rancangan Acak Kelompok (RAK) dan data yang diperoleh dianalisis menggunakan analisis ragam (anova) dengan menggunakan program SAS. R. solanacearum kurang berkembang baik di rumah kaca sehingga tingkat kejadian penyakitnya cukup rendah. Gabungan antara bakteri endofit dan PGPR kurang efektif dalam menekan perkembangan penyakit layu bakteri di lapangan. Aplikasi gabungan antara PGPR dan endofit juga tidak mempengaruhi pertambahan tinggi tanaman dan bobot kering. Bakteri endofit S. epidermidis (BC4) bersifat antagonis jika dikombinasikan dengan bakteri PGPR P. fluorescens RH4003 dan B. subtilis AB89.
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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: 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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