Judul: Fungus Pathogenicity Test and Identification that causes Leaf Disease on Sengon in Dramaga Bogor Permanent Nursery
Abstrak: Sengon (Paraserianthes falcataria (L.) Nielsen) merupakan jenis pohon cepat tumbuh (fast-growing species) dan mudah didapat karena sudah banyak dibudidayakan di Indonesia. Usaha perbanyakan sengon melalui kegiatan pembibitan di persemaian banyak menemui kendala penyakit. Penelitian ini bertujuan mengidentifikasi cendawan penyebab penyakit daun pada tanaman sengon, serta menghitung luas dan intensitas serangan cendawan penyebab penyakit daun pada sengon di Persemaian Permanen Dramaga Bogor. Metode penelitian ini adalah rangkaian uji patogenisitas meliputi pengamatan lapang, postulat Koch, dan identifikasi jenis cendawan. Penelitian menggunakan Rancangan Acak Lengkap Faktorial (RALF). Gejala penyakit yang ditemukan pada daun sengon umur sekitar dua bulan yang ada di lokasi pengamatan adalah penyakit gugur daun, bercak daun, dan hawar daun. Hasil identifikasi cendawan penyebab gugur daun adalah Rhizoctonia sp., cendawan penyebab bercak daun adalah Colletotrichum sp., dan cendawan penyebab hawar daun adalah Fusarium sp.. Fusarium sp. menghasilkan persentase serangan tertinggi dengan luas serangan sebesar 67,34% dan intensitas serangan sebesar 57,28%., Sengon (Paraserianthes falcataria (L.) Nielsen) is a fast-growing tree species and easy to obtain because it has been widely cultivated in Indonesia. Sengon plant propagation is carried out through nursery activities in nurseries. The study aimed to identify the fungus that causes leaf disease on sengon plants and calculate the extent and intensity of attacks by the fungus that causes leaf disease on sengon in the Dramaga Bogor Permanent Nursery. This research method carried out pathogenicity test activities, including field observations, Koch's postulates, and the identification of fungal species. The study used a Completely Randomized Factorial Design (RALF). The disease symptoms found on around two months of sengon leaves old at the observation site were leaf fall, leaf spot, and leaf blight. The results of identifying the fungus that causes leaf fall were Rhizoctonia sp.. This fungus that causes leaf spots is Colletotrichum sp., and the fungus that causes leaf blight is Fusarium sp.. Fusarium sp. resulted in the highest percentage of attacks, with a disease incidence of 67,34% and disease severity of 57,28%.
Keyword: characteristics, identification, Koch's postulates, morphology

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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