Judul: Identifikasi penyebab penyakit hawar daun tanaman buah merah (pandanus conoideus lamk.) dan pengendaliannya menggunakan bakteri rizosfer
Abstrak: Red Fruit (Pandanus conoideus Lamk.) is an endemic plant in Papua, which is used for food and as pharmaceutical substance. A leaf blight disease of red fruit is occurred in Manokwari District. The symptom begins with a small spot and gradually enlarges into brown blight with dark brown at the center and surrounded by a yellow “halo”. The causal agent of the disease was not yet identified. This study was conducted to identify the pathogen of leaf blight based on morphology and molecular characters, to observe the abundance of rhizosphere bacteria and its ability as biocontrol agent. Based on Koch’s Postulates, morphological characterization, PCR and sequencing of 28S rDNA, the causal agent of leaf blight is identified as Fusarium sp. The fungal pathogen shows different characters from that of other Fusarium isolated from watermelon, melon, tomato, banana and jackfruit. Some heat tolerant bacteria isolates, chitinolytic bacteria isolates and a fluorescence bacterium originated from the rhizosphere of red fruit show ability to inhibit the growth of the pathogen.
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Judul: Seleksi dan Identifikasi Bakteri Rizosfer yang Berpotensi sebagai Agens Antagonis Fusarium oxysporum pada Bawang Merah yang diberi Kombinasi Pupuk Organik dan Anorganik.
Abstrak: Penyakit layu fusarium merupakan salah satu penyakit penting tular tanah yang bisa menurunkan produksi bawang merah. Pupuk organik memiliki kelebihan diantaranya memperbaiki sifat fisik, kimia dan biologi tanah sehingga dapat meningkatkan aktivitas mikroba pada tanah yang berperan sebagai antagonis terhadap penyakit layu fusarium. Penelitian ini bertujuan mendapatkan isolat bakteri antagonis yang potensial mengendalikan penyakit layu fusarium (Fusarium oxysporum) dari pertanaman bawang merah yang diberi kombinasi pupuk organik dan anorganik. Sampel yang digunakan dalam penelitian berupa sampel tanah yang diperoleh dari Sukorejo, Nganjuk Jawa Timur. Hasil penelitian menunjukkan bahwa penggunaan pupuk organik dan kombinasinya dengan pupuk anorganik mempengaruhi populasi bakteri rizosfer. Sebanyak 71 isolat dari 512 isolat hasil isolasi, tidak bersifat fitotoksik dan patogenik terhadap mamalia setelah dilakukan uji hipersensitif pada daun tembakau dan uji hemolisis pada media agar darah. Uji daya hambat in vitro kandidat agens antagonis dilakukan dengan metode kultur ganda dan uji produksi senyawa volatil. Berdasarkan hasil uji in vitro diperoleh sebanyak 9 isolat yang berpotensi sebagai antagonis dan memiliki persentase daya hambat di atas 30%. Isolat yang paling tinggi penghambatannya adalah isolat bakteri P1A4B47. Identifikasi berdasarkan analisis sekuen nukleotida gen 16S rRNA hasil sekuensing produk PCR dengan primer 27F dan 1492R menunjukkan bahwa isolat bakteri P1A4B47 memiliki derajat kemiripan sebesar 99.26% dengan Pseudomonas aeruginosa.
Keyword: agens biokontrol, bakteri antagonis, bawang merah, PHT, Pseudomonas aeruginosa

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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