Judul: Bacterial Wilt Disease of Eucalyptus pellita: Disease Trigger Factors, Pathogen and Host Plants Diversity
Abstrak: The productivity of forest plantations such as Eucalyptus pellita in Indonesia is low, one of which is severely affected by bacterial wilt disease. The serious threat of this disease in Indonesia began in 2006, which attacked lowland eucalyptus plantations in Jambi. The disease has been widely spread in Riau, South Sumatra and East Kalimantan provinces. However, studies of bacterial wilt disease on E. pellita in Indonesia are still inadequate, particularly regarding to the integration of site and genetic factors; thus, a comprehensive study is required. The main objective of this study was to analyze the dominant variables of sylviculture, soil properties, and climate factors that can trigger bacterial wilt disease epidemics on eucalypts; identify and describe the phenotypic and genotypic diversity of the causal agent; characterize pathogen strains that have the highest virulence level based on phenotype and genotype diversity; evaluate the resistance of eucalyptus progenies and clones, and analysis SSR markers related to eucalyptus resistance to bacterial wilt disease. The surveys in four provinces in Indonesia showed that bacterial wilt incidence on E. pellita varied from 0–33.5% in plants aged 2–23 months. The initial disease symptoms are yellowing of the leaves followed by branches wilting and causing plant death. Color changes, turning blackish-brown, occurred in the inner cortex of the stem associated with bacterial ooze. Analysis of the triggering factors that contribute to the emergence of bacterial wilt disease was carried out on silvicultural factors (e.g. topography, site classification, diversity eucalyptus clones, seedling propagation technique, plant age, crop rotation, weed cover, incidence of root malformations, and expose to herbicide drift), soil properties (e.g. pH, C-org, N-total, P-available, S-total, Ca2+, Mg+, K+, Na+, and % soil texture) and climate variables (e.g. temperature, humidity, and rainfall). In silvicultural factors, three of the nine variables showed a significant correlation to disease incidence. The variables were plant age, eucalyptus clones, and root malformations incidence. The early growth of eucalyptus plants is a critical period of the disease epidemic, especially in susceptible. For the soil property factor, the soil texture variable is the dominant variable that partially associated with the disease incidence. The incidence of moderate and severe disease generally develops in clay loam soils. Meanwhile, for climatic factors, rainfall has a positive correlation with bacterial wilt incidence. Description of the diversity of pathogens that cause bacterial wilt is carried out by phenotypic and genotypic analyses. The phenotypic diversity analysis included biovar, exopolysaccharide quantification, and virulence tests, while genotypic diversity included phylotypes and sequevar determination based on egl gene sequences. A total of 35 strains were isolated from the field and nurseries. All isolates were confirmed as Ralstonia species complex based on morphological characteristics and molecular studies using species-specific primers. These pathogen strains were dominantly classified as biovar 3 and 4 and had a high variation in virulence and EPS production (0.13 - 8.38 g/mL). Based on the alignment of the egl gene sequences, 29 strains of Ralstonia originating from E. pellita belonged to Phylotype I and were grouped into four sequevars (sequevars 14, 17, 18, 30) and one new sequevar 58. New sequevars were identified
Keyword: epidemi, silvikultur, Ralstonia pseudosolanacearum, klon tahan, marka molekuler

Judul: Inventarisasi Hama dan Penyakit pada Pembibitan Tanaman Eucalyptus di Sentra Pembibitan 2 PT RAPP, Kabupaten Pelalawan, Riau
Abstrak: Perkembangan industri pulp dan kertas di Indonesia terus meningkat dari tahun ke tahun sehingga perlu adanya teknologi dan bahan baku yang cukup serta memadai. Bahan baku yang umumnya digunakan berupa jenis kayu hardwood yang telah dipersiapkan di area Hutan Tanaman Industri (HTI). Tanaman Eucalyptus sp. merupakan salah satu jenis tanaman prioritas yang dikembangkan dalam pengelolaan HTI yang diperuntukkan sebagai kayu serat. Salah satu masalah yang dapat mengganggu pertumbuhan tanaman dan mengakibatkan kerugian adalah serangan dari organisme pengganggu tanaman (OPT). Dalam beberapa kasus, serangan penyakit pada tanaman dapat mengakibatkan terhambatnya pertumbuhan tanaman, menurunnya kualitas kayu, bahkan kematian tanaman. Penelitian bertujuan mengetahui jenis-jenis hama dan penyakit, serta budi daya tanaman Eucalyptus dari sampel bibit bergejala yang diambil dengan metode purposive sampling di Sentra Pembibitan 2 PT RAPP, Kecamatan Pangkalan Kerinci, Kabupaten Pelalawan, Riau. Identifikasi patogen dilakukan dengan membandingkan hasil pengamatan gejala serta tanda di lapangan dan laboratorium dengan literatur. Inventarisasi hama dilakukan dengan studi literatur berdasarkan data hama ditemukan yang telah tersedia. Penyakit yang menyerang bibit Eucalyptus adalah bercak daun Quambalaria, bercak daun dan batang Cylindrocladium, bercak daun Kirramyces, layu pucuk dan daun Rhizoctonia, dan hawar daun Xanthomonas. Hama yang ditemukan menyerang bibit tanaman Eucalyptus, yaitu ulat penggulung daun (Strepsicrates macroptena), tungau, kutu kebul (eucalyptus whitefly), thrips (Thrips autralis), wereng, kutu daun, dan Helopeltis theivora., The development of the pulp and paper industry in Indonesia continues to increase from year to year, which requires adequate technology and raw materials. Raw materials that are generally used are hardwood species that have been prepared in the Industrial Plantation Forest (HTI) area. Eucalyptus sp. is one of the priority plant species developed in HTI management which is intended as fiber wood. One of the problems that can interfere with plant growth and cause losses is the attack of plant pest organisms (OPT). In some cases, disease attacks on plants can result in inhibition of plant growth, decreased wood quality, and even plant death. This study aims to determine the types of pests and diseases, as well as the cultivation of Eucalyptus from symptomatic seedling samples taken by purposive sampling method at PT RAPP Nursery Center 2, Pangkalan Kerinci District, Pelalawan Regency, Riau. Pathogen identification was carried out by comparing observations of symptoms and signs in the field and laboratory with the literature. Pest inventory was conducted by literature study based on available pest data. Diseases that attack Eucalyptus seedlings are Quambalaria leaf spot, Cylindrocladium leaf and stem spot, Kirramyces leaf spot, Rhizoctonia shoot and leaf wilt, and Xanthomonas leaf blight. Pests found attacking Eucalyptus seedlings were leafroll caterpillars (Strepsicrates macroptena), mites, whitefly (eucalyptus whitefly), thrips (Thrips autralis), leafhoppers, aphids, and Helopeltis theivora.
Keyword: Eucalyptus sp., industrial forest plantations, pathogens, diseases

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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