Judul: Pengujian Bacillus thuringiensis galur SAHA 12.08 sebagai pengendali pertumbuhan cendawan penyebab bercak daun kelapa sawit
Abstrak: Oil palm (Elaeis guineensis Jacq.) is one of major agriculture commodities in Indonesia. The disease caused by pathogenic fungi such as Curvularia affinis and Colletotrichum gloeosporoides could inhibit the growth of oil palm seedling plants. Cell wall, mycelia cells, stalks, and conidium of fungi that composed by chitin, can be degraded by chitinolytic bacteria through its ability to produce the chitinase enzyme. This research was aimed to study the ability of Bacillus thuringiensis strain SAHA 12.08 in inhibiting C. affinis and C. gloeosporoides that attacked oil palm leaf through in vitro experiment. Bacillus thuringiensis strain SAHA 12.08 showed inhibitor activity to pathogenic fungi using 24 hour and 12 hour bacteria culture. Result of inhibition test using Detached-Leaf Assays method showed that capability of Bacillus thuringiensis as biocontrol activity against C. affinis was 85% and 90%, and against C. gloeosporoides was 96% and 59%. Inhibition of the strain against C. affinis and C. gloeosporoides using in vitro test were 27,8% and 28,2 % respectively. Bacillus thuringiensis strain SAHA 12.08 had antagonistic activity at in vitro test using leaf of oil palm and showed biocontrol activity against C. affinis and C. gloeosporoides
Keyword: Bogor Agricultural University (IPB), oil palm, C. gloeosporoides, C. affinis, Chitinolytic bacteria

Judul: Isolation of Chitinolytic Bacteria Used as Biological Control of Suspected Pathogenic Fungi on Oil palm Seedlings
Abstrak: Kelapa sawit (Elaeis guineensis Jacq.) merupakan salah satu komoditas perkebunan utama di Indonesia. Produksi kelapa sawit sangat dipengaruhi oleh berbagai faktor lingkungan seperti curah hujan, tanah, iklim, dan serangan penyakit. Serangan penyakit seperti antraknosa dan bercak daun menyebabkan pembusukan pada daun kelapa sawit saat pembibitan yang pada akhirnya akan membunuh tanaman kelapa sawit tersebut. Upaya pencegahan serangan penyakit pada kelapa sawit yang disebabkan oleh cendawan patogen dapat dilakukan dengan penggunakan bakteri kitinolitik yang mampu menghasilkan enzim kitinase sebagai pengendali biologi. Kitin merupakan salah satu komponen penyusun dinding sel dari cendawan. Penelitian ini bertujuan untuk mengisolasi bakteri kitinolitik dan menguji potensinya sebagai pengendali hayati dalam keadaan in vitro terhadap cendawan patogen pada kelapa sawit. Hasil menunjukkan isolat SAHA12.08, SAHA12.10, dan SAHA12.13 memiliki aktivitas antagonis terhadap pertumbuhan cendawan yang diduga patogen Curvularia sp. dan Colletotrichum sp., sedangkan isolat KAHN15.12 hanya memiliki aktivitas antagonis terhadap pertumbuhan Curvularia sp. yang diduga patogen.
Keyword: aktivitas antagonis, cendawan patogen, kelapa sawit, kitinolitik

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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