Judul: Identification and Pathogenicity Test of the Causes of Leaf Blight Disease in Teak at PT. Solusi Bangun Indonesia Nursery
Abstrak: Jati (Tectona grandis Linn) merupakan tanaman dari famili Verbenaceae yang digunakan sebagai tanaman revegetasi karena adaptif pada lahan kritis, tahan terhadap penyakit dan bernilai ekonomi tinggi. Permasalahan penyakit jati banyak terjadi di persemaian. Penelitian ini bertujuan untuk mengidentifikasi patogen penyebab penyakit hawar daun di Persemaian PT. SBI. Metode penelitian dilakukan dengan sensus di lapangan dan uji postulat Koch. Ditemukan hawar daun dengan luas serangan sebesar 93%, dengan ciri nekrosis. Empat isolat yang diberi kode S1, S2, S3, dan S4 didapatkan dengan uji postulat Koch. Hasil identifikasi cendawan menunjukkan bahwa isolat S1 dan S2 adalah Rhizoctonia sp. dengan ciri karakteristik hifa bersekat, sudut percabangan 90°, miselia sterilia dan memiliki struktur moniloid. Isolat S3 dan S4 adalah Curvularia sp. dengan ciri keberadaan hifa yang bersepta dan konidia yang terdiri atas 4-5 sel membentuk rantai., Teak (Tectona grandis Linn) is a plant from the Verbenaceae family used for revegetation due to its adaptability to critical lands, disease resistance, and high economic value. Problems with teak diseases frequently occur in nurseries. This study aims to identify the pathogens causing leaf blight disease in the nurseries of PT. SBI. The research methods included field surveys and Koch's postulates tests. Leaf blight with an attack rate of 93% was found, characterized by necrosis. Four isolates, coded S1, S2, S3, and S4, were obtained through Koch's postulates tests. Fungal identification results showed that isolates S1 and S2 were Rhizoctonia sp., characterized by septate hyphae, 90° branching angles, sterile mycelia, and monilioid structures. Isolates S3 and S4 were Curvularia sp., characterized by septate hyphae and conidia consisting of 4-5 cells forming chains.
Keyword: Agaricomycetes, Dothideomycetes, postulat Koch, patogenesitas, nekrosis

Judul: Pathogenicity Test of Fungal Leaf Blight on Sengon Seedlings at Permanent Nursery Dramaga Bogor
Abstrak: Sengon (Paraserianthes falcataria L. Nielsen) merupakan tanaman dari famili Fabaceae yang memiliki banyak potensi, baik secara ekologi dan ekonomi untuk ditanam di lahan rehabilitasi. Penelitian ini bertujuan untuk menguji patogenisitas dan mengidentifikasi cendawan penyebab hawar daun pada bibit sengon. Metode penelitian meliputi kegiatan uji patogenisitas yang terdiri atas pengamatan lapang dan postulat Koch serta identifikasi jenis. Penelitian menggunakan Rancangan Acak Lengkap Faktorial (RALF) dengan uji ANOVA dan uji lanjut Duncan. Hasil uji postulat Koch dapat diketahui bahwa dua isolat menyebabkan hawar pada daun. Hasil uji patogenisitas dapat diketahui bahwa isolat 1 menghasilkan luas serangan dan intensitas serangan paling tinggi dan berbeda nyata dengan isolat lainnya. Hasil identifikasi dapat diketahui bahwa isolat 1 memiliki karakteristik koloni berwarna putih, terdapat sklerotium, tidak memiliki spora, sudut percabangan hifa 90°, bersekat, terdapat penggentingan hifa dekat percabangan, dan terdapat struktur moniloid. Berdasarkan karakteristik tersebut, cendawan ini merupakan Rhizoctonia sp.
Keyword: Characteristics, Koch's postulate, leaf blight, Paraserianthes falcataria, Rhizoctonia sp.

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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