Judul: Intensitas Penyakit Penting, Deteksi Huanglongbing Dan Pengaruh Aplikasi Pgpr Pada Tanaman Jeruk Di Kabupaten Bogor
Abstrak: Jeruk adalah salah satu tanaman holtikultura penting dan mempunyai nilai ekonomi tinggi di Indonesia. Salah satu permasalahan penting yang dihadapi dalam budidaya jeruk adalah adanya penyakit tanaman yang mengakibatkan penurunan kualitas dan kuantitas hasil. Tujuan penelitian ini adalah mengamati penyakit-penyakit umum tanaman jeruk di Kabupaten Bogor, Provinsi Jawa Barat, deteksi penyakit huanglongbing dan melihat pengaruh aplikasi plant growth promoting rhizobacteria (PGPR) pada fase vegetatifnya. Tahapan penelitian meliputi pengamatan intensitas dan identifikasi penyakit yang ditemui di lapang, aplikasi PGPR pada tanaman jeruk fase vegetatif untuk mengetahi pengaruhnya terhadap intensitas penyakit jeruk. Selanjutnya, pengamatan berdasarkan peubah agronomi tanaman yang dilakukan setiap minggu selama 10 minggu pengamatan. Khusus untuk penyakit huanglongbing, yang juga dikenal sebagai CVPD, dilakukan pengamatan gejala eksternal serta gejala internal melalui uji akumulasi pati pada jaringan floem yang diambil dari tulang daun tanaman jeruk dan deteksi secara molekuler dengan teknik polymerase chain reaction (PCR). Berdasarkan pengukuran Area􀀃���������􀀸���������nder􀀃���������􀁗���������􀁋���������􀁈��������� 􀀧���������isease􀀃���������􀀳���������rogress 􀀦���������urve (AUDPC) ditunjukkan bahwa penyakit yang paling dominan pada fase vegetatif dan generatif adalah embun jelaga (Meliola sp.) dan penyakit kudis (Elsinoe fawcetti). Aplikasi PGPR memberikan perubahan tidak signifikan terhadap perubahan intensitas penyakit dibandingkan dengan tanaman jeruk yang tidak diberi perlakuan, tetapi dapat mempengaruhi pertumbuhan dan perkembangan tanaman jeruk. Penyakit huanglongbing ditemukan dalam insidensi yang rendah. Diagnosis huanglongbing dari gejala internal ditunjukkan dengan adanya akumulasi pati pada jaringan floem, namun tidak selalu memberikan hasil uji PCR yang positif.
Keyword: CVPD, huanglongbing, penyakit jeruk, PGPR, polymerase chain reaction

Judul: Optimasi Deteksi Penyakit Huanglongbing pada Tanaman Jeruk Menggunakan Teknik Polymerase Chain Reaction
Abstrak: Citrus is an important horticultural commodity with high economic value in many countries. Huanglongbing disease, or in Indonesia known as citrus vein phloem degeneration caused by Liberobacter asiaticus bacterium, is a major factor limiting citrus production in many Asian countries. The disease detection and diagnosis solely based on its symptom is sometimes not reliable since it resembles to those caused by nutrient deficiencies. Detection using polymerase chain reaction is an accurate technique for many plant pathogens including the huanglongbing causal agent. The research objectives are to observe huanglongbing disease of citrus, based on external and internal symptoms, in Bogor and to optimize PCR technique for detection of the pathogen. The disease identification and detection based on the external symptom showed that there was less specific character which correlated with pathogen presence in the sample. Symptom of the infected plants is leaf discoloration and deformation. The leaves showing symptoms of chlorosis, are smaller and more lancet than leaves without chlorosis symptoms. The results of detection based on internal symptom showed as starch accumulation in phloem are consistent with that of PCR. The optimization of detection using PCR showed that the most effective and efficient extraction method to obtain DNA template was a modification of Dellaporta et al. (1986) with extraction buffer concentration at 2 times. After 2 weeks period of storage treatment at 4 oC, Huanglongbing disease can still be detected by PCR, but its DNA bands showed inconsistency among three replications. The most optimum two weeks sample preservation is at 4 oC, whereas preservation with CTAB buffer still maintain the sample to yield DNA template adequately for PCR
Keyword: PCR., huanglongbing, DNA extraction, detection, CPVD

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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