Judul: Intensity of Main Disease in Several Superior Clones at Krebet Baru Sugar Factory, Malang
Abstrak: Tebu (Saccharum officinarum L.) merupakan tanaman perkebunan penting di Indonesia sebagai penghasil gula utama. Pada tahun 2018 produksi gula tebu mengalami penurunan sebesar 19,25 ribu ton dibandingkan tahun 2017, yaitu 2,17 juta ton. Penurunan tersebut tidak sejalan dengan konsumsi gula tebu yang kian meningkat dari tahun ke tahun. Penelitian banyak dilakukan untuk mendapatkan varietas-varietas tebu unggul yang diharapkan memiliki produksi tinggi dan tahan terhadap faktor-faktor gangguan yang dapat menurunkan produksi tanaman. Varietas-varietas tebu unggul tersebut perlu dievaluasi untuk mengetahui responnya terhadap penyakit-penyakit utama tebu yang dapat menurunkan rendemen tebu, yaitu penyakit mosaik bergaris (Sugarcane streak mosaic virus/SCSMV), pokahbung (Fusarium moniliforme Sheldon), dan luka api (Sporisorium scitamineum Sydow). Pengamatan intensitas penyakit dilakukan di Pabrik Gula Krebet Baru, Malang pada 14 klon tebu unggul setiap 2 minggu selama 3 bulan. Sampel tanaman yang menunjukkan gejala penyakit dibawa ke laboratorium untuk deteksi penyebab penyakitnya. Gejala penyakit mosaik bergaris yang ditemukan berupa garis-garis mosaik sejajar dengan tulang daun yang tidak beraturan, penyakit pokahbung berupa klorosis pada daun muda, dan luka api berupa anakan yang menyerupai rumput serta cambuk api. Penyakit mosaik bergaris terjadi pada tiga klon tebu, yaitu klon 1, 3, dan 14, dengan intensitas berturut-turut 8,33%, 33,33%, dan 63,89%. Intensitas penyakit pokahbung berkisar antara 2,78% sampai 22,22%. Intensitas penyakit luka api berkisar antara 11,11% sampai 25%. Konfirmasi keberadaan patogen mosaik bergaris dengan metode polymerase chain reaction berhasil mengamplifikasi pita DNA SCSMV berukuran ~500 pb. Keberadaan patogen pokahbung terkonfirmasi dengan tumbuhnya cendawan F. moniliforme melalui proses isolasi dan patogen luka api terkonfirmasi dengan terlihatnya hifa S. scitamineum pada jaringan meristem tebu. Klon 8 dan 12 menunjukkan respons toleran hingga tahan terhadap ketiga penyakit tersebut dan dapat direkomendasikan sebagai klon potensial dalam mengendalikan penyakit utama tebu pada penanaman selanjutnya., Sugarcane (Saccharum officinarum L.) is an important plantation crop in Indonesia as the major source of sugar production. Cane sugar production decreased significantly in recent years and it is not in line with the demand of cane sugar which is increasing from year to year. Many studies have been carried out to obtain sugarcane varieties which are expected to have high production and are resistant or tolerant to factors constraining crop production. Therefore, research was conducted to evaluate the response of 14 potential sugarcane varieties to the main sugarcane diseases, i.e. sugarcane streak mosaic (Sugarcane streak mosaic virus/SCSMV), pokkah boeng (Fusarium moniliforme Sheldon), and sugarcane smut (Sporisorium scitamineum Sydow). Observations of disease intensity were carried out at the Krebet Baru Sugar Factory, Malang every 2 weeks for 3 months. Samples of diseased plants were taken to the laboratory for further confirmation of the target pathogens. Spesific symptoms of sugarcane streak mosaic, pokkah boeng and sugarcane smut diseases were observed in the field involving mosaic, chlorosis on young leaves and smut, respectively. Mosaic symptom was found only on 3 clones with disease intensity ranging from 8.33% to 68.89%; whereas chlorosis and smut symptom was found on 11 and 14 clones with disease intensity ranging from 2.78% to 22.22% and 11.11% to 25%, respectively. Laboratory examinations confirmed SCSMV infection by polymerase chain reaction method, pokkah boeng disease by the growth
Keyword: Fusarium, Luka api, Mosaik bergaris, PCR, Pokahbung, SCSMV, Sporisorium scitamineum

Judul: Effects of Weather Factors to the Incidence and Rate of Infection of Smut Disease on Some Prime Varieties of Sugarcane at Indonesian Sugar Research Institute (ISRI) Pasuruan
Abstrak: Tanaman tebu (Saccharum officinarum L.) merupakan komoditas perkebunan yang penting sebagai bahan baku utama dalam produksi gula. Penurunan produksi tebu disebabkan oleh berbagai faktor yang salah satunya yaitu penyakit tebu. Salah satu penyakit penting pada tebu adalah cendawan Sporisorium scitamineum yang merupakan penyebab penyakit luka api. Penyakit ini menjadi penyakit utama pada tanaman tebu karena dapat menimbulkan kerugian yang cukup berarti dan saat ini menjadi permasalahan utama pada pertanaman tebu di Indonesia. Tujuan penelitian ini adalah untuk menganalisis hubungan faktor cuaca terhadap kejadian penyakit luka api, serta memberikan informasi data terbaru terkait insidensi dan laju perkembangan penyakit luka api. Penelitian dilakukan melalui tahapan-tahapan sebagai berikut survei penentuan lokasi dan penentuan sampel pengamatan, pengamatan insidensi dan perkembangan penyakit, perhitungan perkembangan laju, AUDPC, faktor cuaca dan analisis data. Hasil pengamatan menunjukkan insidensi luka api tertinggi terjadi pada varietas PS 094 dengan nilai 8,85% dan terendah pada varietas PSKA 942 serta PS 881 dengan nilai 0% (tidak ada kejadian penyakit). Laju perkembangan penyakit tertinggi terjadi pada varietas Bululawang sebesar 0,009 (unit/2 minggu) dan yang terendah pada varietas PSKA 942 serta PS 881 dengan laju perkembangan penyakit 0 (unit/2 minggu)., Sugarcane (Saccharum officinarum L.) is an important estate crop as the main raw material for sugar production. The decline in sugarcane production can be caused by various factors, one of which is sugarcane diseases. One of the important diseases on sugarcane is smut caused by the fungus Sporisorium scitamineum. The disease is a major disease in sugarcane because it causes significant yield losses and currently the disease becomes a serious problem in sugarcane plantation. The purpose of this study was to analyze the effects of weather factors to the incidence of smut, as well as provide the latest data information regarding the incidence and disease development. A research activity was conducted by some steps as followed: surveys to determine the location and determine the observation samples, observation of disease incidence and its development, disease rate calculation, AUDPC, weather factors and data analysis. The highest incidence of smut occured on PS 094 variety was up to 8.43% and the lowest was 0% on PSKA 942 and PS 881 varieties. The highest infection rate was up to 0.009 (units/2 weeks) on the Bululawang variety while the lowest was on 0 (units/2 weeks) that was showed by PSKA 942 and PS 881 varieties.
Keyword: AUDPC, Bululawang, PS 881, PS 094, Sporisorium scitamineum

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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