Judul: Pengaruh varietas, pupuk daun dan dosis pupuk daun terhadap perkembangan penyakit busuk hitam bakteri (Xanthomonas compestris (Pamm.) Dye.) pada kubis telur (Brassica oleraceae var. capitata Linn.)
Abstrak: Penelitian ini bertujuan untuk mengetahui pengaruh pupuk daun Supergro, Vitabloom Spesial 30-10-10 dan Mamigro 21-21-21 pada berbagai tingkat dosis terhadap perkembangan penyakit busuk hitam bakteri pada kubis telur varietas Green Coronet, K.K. Cross dan Gloria Osena. Penelitian dilakukan di rumah plastik dengan menggu- nakan polibag, tanah steril, pupuk Urea, TSP, dan KCl. Rancangan Percobaan yang digunakan adalah Rancangan Acak Lengkap Faktorial. Inokulum bakteri X. campestris diperoleh dari tanaman kubis yang menunjukkan gejala busuk hitam bakteri di daerah Segunung, Cianjur. Inokulasi dilakukan dengan metode penyemprotan pada tanaman kubis berumur 5 minggu setelah tanam. Gejala khas penyakit tampak jelas 10 hari setelah inokulasi. Varietas kubis berpengaruh sangat nyata terhadap in- tensitas serangan patogen dan panjang bercak. Intensitas serangan makin tinggi dan bercak makin panjang dengan ber- tambahnya umur tanaman. K.K. Cross menunjukkan intensitas serangan paling rendah dan bercak paling pendek. yang diberi pupuk menunjukkan intensitas serangan lebih rendah daripada tanaman tanpa pupuk. Interaksi varietas dan dosis pupuk daun berpengaruh nyata terhadap panjang bercak. Interaksi Green Coronet dan tanpa pupuk menunjukkan bercak lebih pendek daripada interaksi lainnya. Interaksi K.K. Cross dan tanpa pupuk menunjukkan bercak lebih panjang daripada interaksi lain- nya. Pengaruh interaksi varietas dan dosis pupuk daun terhadap tinggi tanaman dan lebar tajuk tampak nyata pada minggu I. Tanaman yang lebih tinggi ditunjukkan oleh interaksi Green Coronet dan dosis di atas anjuran. Tajuk paling sempit ditunjukkan oleh interaksi Green Coronet dan tanpa pupuk.
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Judul: Keefektifan ekstrak empat jenis tumbuhan dan kitosan terhadap xanthomonas campestris pv.campestris penyebab penyakit busuk hitam pada kubis
Abstrak: The aims of this study were to detect of X. campestris pv. campestris from five cabbage cultivars, to test the effectiveness of plant extracts and chitosan in inhibiting the growth of X. campestris pv. campestris, to test the effectiveness of seed treatment using plant extracts and chitosan to control X. campestris pv. campestris in infected cabbage seeds, and to evaluate the effect of seed treatment to seed viability. The results of this research showed that betel extract, clove extract, and chitosan had ability to inhibit X. campestris pv. campestris growth, while binahong and turmeric extracts did not show inhibitory effect. Cabbage seed cultivar Green Hero was positively infected by X. campestris pv. campestris. X. campestris pv. campestris developed yellowish green colonies on SX medium. DNA fragment of 535 bp was successfully amplified using PCR with spesific primer for hrpF gene of X. campestris pv. campestris, i.e. XCF and XCR. The treatment with 2% betel extract, 3% clove extract, and 0.5% chitosan totally inhibited bacterial growth in NB medium and suppressed over 99% inoculum density after 50 minutes soaking seed. Betel and clove extracts suppressed the infection rate on seed by 84% and 97.33%, respectively. Chitosan did not reduce the level of infection due to the high initial infection of seeds. The treatments did not decrease seed viability as indicated by seed germination rates (95%). It was evidenced that betel extract, clove extract, and chitosan have the potential to be developed as quarantine treatment techniques to suppress infection of X. campestris pv. campestris in cabbage seeds.
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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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