Judul: Identifikasi Spesies Begomovirus Penyebab Penyakit Daun Kuning pada Tanaman Mentimun melalui Analisis Sekuen Nukleotida
Abstrak: Yellow vein mosaic disease on Cucurbitaceae is known to be associated with infection of Tomato leaf curl NewDelhi virus (ToLCNDV) or Squash leaf curl China virus (SLCCNV). Last year, a yellowing disease with typical vein banding without any leaf malformation on cucumber (Cucumis sativus) in Bali was found to be induced by SLCCNV. This year, cucumber cultivation in West Java was affected by severe incidence of a disease resemble with that occurred in Bali. This research aimed to elucidate if the disease on cucumber plants emerged in West Java is also caused by SLCCNV. Total nucleic acid extractions of cucumber leaves collected from three villages in Bogor (Cikarawang, Petir, and Sindangbarang) were made separately and used for PCR amplifications using a pair of primers (SPG1: 5'-CCCCKGTGCGWRAATCCAT-3' and SPG2: 5'- ATCCVAAYWTYCAGGGAGCTAA-3') designed to match the sequences of the DNA-A of Begomovirus. PCR from all three samples yielded amplified DNA fragments of the expected sizes of 912 bp, indicated the association of the virus with the disease. The DNA sequence of the PCR products shared more than 95% sequence identity with ToLCNDV isolates available in the GenBank and clustered with them in the phylogenetic analysis. This finding confirmed that SLCCNV was not spread yet (from Bali) to West Java
Keyword: Polimerase chain reaction, Tomato leaf curl NewDelhi virus, yellowing disease

Judul: Karakterisasi Begomovirus Penyebab Penyakit Daun Keriting pada Mentimun (Cucumis sativus L.)
Abstrak: Cucumber (Cucumis sativus L.) is an important vegetable crops in Indonesia. Productivity of cucumber affected by inefficient and ineffective cultural practices in addition to the problems with pests and diseases. One of important disease on cucumber that has the potential to effect the production is leaf curl disease caused by Begomovirus. Leaf curl diseases caused by Begomovirus has been reported on several crops in Indonesia and become a serious concern effecting yield loss. Tobacco plantation in East Java suffered 30% damage from infection of Tobacco leaf curl begomovirus in 1984. Since early 2000 infection of Pepper yellow leaf curl begomovirus on chillipepper has been reported in West and Central Java and disease management for this yellow disease on chillipepper has not been achieved successfully. Tomato yellow leaf curl begomovirus was also reported to cause epidemic on tomato plants in West and Central Java. Recently, leaf curl disease was observed in cucumber plants especially in Klaten, central Java. Similar disease was reported earlier since 1996, and virus identification showed that nucleotide sequence of the virus has high similarity with Tomato leaf curl New Delhi begomovirus (TLCV-New Delhi). Infection of Begomovirus on Cucurbitaceae has actually became problems in several countries, for instance Squash leaf curl begomovirus caused leaf curl disease on squash (Cucurbita maxima) and Watermelon curly mottle begomovirus caused yellow leaf and dwarfing on melon (C. melo) in United States. Begomovirus is only transmitted by whitefly (Bemisia tabaci) as its insect vector and whitefly is known to have a broad host range and capable to colonize a number of plants. Identification and characterization of Begomovirus causing leaf curl disease of cucumber in Java has not been done despite its importance. Studies on host range and transmission of Begomovirus is important in order to develop disease management strategy. The aims of this research is to detect viruses infecting cucumber plants, to identify Begomovirus infected cucumber, to study transmission efficiency of Begomovirus by vector B. tabaci, and to determine the host range. Field observation and samples collection was conducted in West Java (Bogor, Subang), Central Java (Tegal, Sukoharjo), and Yogyakarta (Sleman). Leaves showing typical symptoms of leaf curling, mosaic, blistering and yellowing were collected for further identification. Infection of Begomovirus, SqMV, ZyMV, and CMV was detected from all samples, but no infection of TRSV nor WMV was detected. Mix infection was found, for instance samples from Bogor and Sleman (Kalasan dan Ngemplak) were infected by 4 viruses (Begomovirus, SqMV, ZyMV, dan CMV) and showed more severe symptoms i.e. leaf curling, mosaic, yellowing and blistering. Nucleotide sequences obtained from sequencing of DNA fragments as the amplicon using polymerase chain reaction (PCR) method ranging from 1474 to 1633 bp for TEGAL, KALASAN, NGEMPLAK, SUKOHARJO, and BOGOR isolates. Begomovirus genome amplified using universal primer pAL1v1978/pAR1c715 covers part of replication gene, coat protein gene and common region which is the region of the genome commonly used for identification of Begomovirus. Sequence homology among the five isolates ranging from 96.1% to 99.3%, indicated close relationship. BOGOR isolate showed different symptoms from other isolates and its relationship is not as close
Keyword: Efficiency of transmission, Geminivirus, host range, insect vector, sequence analysis

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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