Judul: Karakterisasi Begomovirus Penyebab Penyakit Daun Keriting pada Mentimun (Cucumis sativus L.)
Abstrak: Mentimun (Cucumis sativus L.) merupakan salah satu sayuran utama yang dibudidayakan oleh petani di Indonesia. Produktivitas mentimun sangat dipengaruhi oleh budidaya yang kurang intensif dan efisien, serta adanya gangguan hama dan penyakit. Salah satu kendala produksi adalah penyakit yang disebabkan oleh infeksi Begomovirus penyebab penyakit daun keriting. Penyakit daun keriting yang disebabkan oleh Begomovirus pada beberapa jenis pertanaman di Indonesia dilaporkan menyebabkan kehilangan hasil sehingga menimbulkan kerugian yang cukup besar. Pertanaman tembakau di Jawa Timur dilaporkan mengalami kerusakan hingga 30% karena infeksi Tobacco leaf curl begomovirus pada tahun 1984. Sejak awal tahun 2000 pertanaman cabai di daerah Jawa Barat dan Jawa Tengah dilaporkan terinfeksi Begomovirus dan sampai sekarang penyakit kuning yang disebabkan oleh Pepper yellow leaf curl begomovirus belum dapat dikendalikan. Tomato yellow leaf curl begomovirus yang menyebabkan epidemi penyakit daun keriting juga menjadi kendala utama dalam meningkatkan produksi tanaman tomat di Jawa Barat dan Jawa Tengah. Akhir-akhir ini penyakit daun keriting yang disebabkan oleh Begomovirus ditemukan pada tanaman mentimun di Kabupaten Klaten, Jawa Tengah. Penyakit yang sama dilaporkan di Thailand sejak tahun 1996, dan virus penyebab penyakit tersebut memiliki kemiripan sikuen nukleotida yang tinggi dengan isolat Tomato leaf curl New Delhi begomovirus (TLCV-New Delhi). Infeksi Begomovirus pada tanaman Cucurbitaceae telah lama menjadi masalah di beberapa negara, diantaranya Squash leaf curl begomovirus menyebabkan penyakit daun keriting pada labu (Cucurbita maxima) dan Watermelon curly mottle begomovirus menyebabkan penyakit daun menguning dan kerdil pada melon (C. melo) di Amerika Serikat. Identifikasi dan karakterisasi Begomovirus penyebab penyakit daun keriting mentimun di Jawa belum dilakukan secara khusus. Begomovirus hanya dapat ditularkan melalui serangga vektor kutukebul (Bemisia tabaci) dan serangga ini dapat mengolonisasi berbagai spesies tanaman. Hal tersebut sangat berbahaya karena akan mendukung terjadinya ledakan penyakit daun keriting. Oleh karena itu, perlu dilakukan penelitian untuk mengetahui sifat-sifat Begomovirus agar dapat menyusun rekomendasi strategi pengendalian penyakit yang tepat untuk mencegah kerugian oleh infeksi Begomovirus. Penelitian dilakukan dengan tujuan untuk mendeteksi virus-virus yang menginfeksi tanaman mentimun, mengidentifikasi Begomovirus yang menginfeksi mentimun, mempelajari efisiensi penularan Begomovirus melalui serangga vektor B. tabaci dan mengetahui beberapa jenis tanaman inang dari Begomovirus yang menginfeksi mentimun. Penelitian meliputi empat kegiatan pokok yaitu pengumpulan sampel tanaman mentimun dan deteksi beberapa virus pada sampel daun mentimun dari lapangan, identifikasi Begomovirus dengan metode molekular, pengujian efisiensi penularan Begomovirus melalui kutukebul, dan pengujian kisaran inang. Pengamatan gejala dan pengambilan sampel tanaman yang terinfeksi Begomovirus dilakukan di daerah Jawa Barat (Bogor, Subang), Jawa Tengah (Tegal, Sukoharjo), dan Daerah Istimewa Yogyakarta (Sleman). Daun mentimun yang dikumpulkan sebagai sampel adalah daun yang menunjukkan gejala daun keriting, mosaik, melepuh, dan menguning. Gejala yang umum terlihat pada pertanaman mentimun meliputi gejala mosaik kuning cerah, mengeriting, melepuh, penebalan tulang daun, dan reduksi ukuran daun. Infeksi Begomovirus, SqMV, ZyMV, dan CMV berhasil dideteksi pada hampir semua sampel daun, namun infeksi TRSV dan WMV tidak terdeteksi pada semua sampel. Infeksi oleh lebih dari satu jenis virus ditemukan pada beberapa sampel daun dari beberapa lokasi. Sampel asal Bogor dan Sleman (Kalasan dan Ngemplak) yang terinfeksi oleh 4 virus (Begomovirus, SqMV, ZyMV, dan CMV) secara bersamaan menunjukkan gejala yang lebih parah dibandingkan sampel lainnya yaitu berupa daun keriting,
Keyword: Analisis keragaman genetik, efisiensi penularan, Geminivirus, kisaran inang, serangga vektor

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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