Judul: Mutagenesis dengan Transposon pada Xanthomonas oryzae pv. oryzae Penyebab Hawar Daun Padi
Abstrak: Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial leaf blight (BLB) disease of rice that can reduce rice productivity. The use of biocontrol agents is an effective solution to solve this problem. The aim of this study was to obtain mutants of Xanthomonas oryzae pv oryzae through transposon mutagenesis. Transposon mini-Tn5Km1 carried by E.coli S-17-1 (λ pir) was introduced into Xanthomonas oryzae pv oryzae STG21 by conjugation diparental mating. Frequency of tranconjugation obtained from this study was about 2.7×10-6, 1.1×10-6, dan 2.4×10-6 at the ratios of 1:1, 1:10, and 10:1 respectively. Five mutants (M93, M99, M107, M112, and M120) out of 300 mutants tested did not cause a hypersensitive reaction on tobacco plants. However, on rice IR64 plants showed that those mutants could reduce the symptoms of BLB with presentage of 96%, 94%, 94%, 91% and 92% respectively.
Keyword: Xanthomonas, mutagenesis, HDB, transposon

Judul: Penapisan Bakteri Filosfer Penghasil Senyawa Bioaktif Anti Xanthomonas oryzae pv. oryzae Penyebab Penyakit Hawar Daun Bakteri pada Padi
Abstrak: Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the important diseases in rice crops. The disease is difficult to control because it attacks the rice plant at different growth stages ranging tillering, flowering and ripening. One alternative that can be used to control the spread of BLB is using the biocontrol agent which can be obtained from phyllosphere. This study aims to isolate, characterize and screen the rice phyllosphere bacteria producing bioactive compounds anti Xoo causes BLB in rice. Phyllosphere bacteria isolated from rice leaves Ciherang healthy age of 2.5 months using 4 different media obtained 285 bacterial isolates, the 65 isolates of King’s B agar, 86 isolates of nutrient agar, 81 isolates of Luria-Bertani agar, and 53 isolates of trypticase soy agar. Antagonist test using double layer method showed 58 isolates phyllosphere bacteria potential as a biocontrol agent producing bioactive compounds Xoo. Pathogenicity test showed 18 isolates not potentially pathogenic to rice plants. Among the 18 non-phytopathogenic isolates, 14 isolates including Gram-positive bacteria, 4 isolates Gram-negative bacteria, and 5 isolates of Bacillus suspected. Three of the 18 isolates (BFSGb 8, BFSGb 55, and BFSGb 99) has the largest index value inhibition of in-vitro against Xoo is 1.33, 1.67, and 1.33 respectively to isolate BFSGb 8, BFSGb 55, and BFSGb 99.
Keyword: Bogor Agricultural University (IPB), Xanthomonas oryzae pv. oryzae., phyllosphere bacteria, bioactive compounds, Bacterial leaf blight

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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