Judul: Seed-Borne Fusarium sp.Causing Damping-off of Pinus tecunumanii Seedlings in Tanzania
Abstrak: Seed-borne fungi are among the most serious groups of pathogens, causing significant losses in both quantity and quality of Pinus seeds. Conifer nurseries serve as reservoirs for a diverse suite of native and exotic pathogens, e.g., Fusarium and Phytophthora spp. These pathogens can move undetected through asymptomatic seedlings and infected nursery stock which can cause mortality in field-planted seedlings and risk of pathogen introductions into plantations. Occurrence of Fusarium spp. is one of the problems, most limiting to growth of seedlings in nurseries. The pathogen can be transmitted via seeds and causes damages to the seedlings during pre- and post-emergence stages. The present study aimed to perform seed health testing of P. tecunumanii through blotter test method and to identify seed-borne pathogens which affect the species and cause damping-off disease. Seed and symptomatic seedlings samples were collected from four different seed lots namely; Private Forestry Programme (PFP), Makungu, Mafinga, and Kilolo. The results came out with four major fungi species which are; Aspergillus niger, Penicillium sp, Rhizopus sp and Fusarium sp. Fusarium sp was suspected to be the major seed-borne fungi which causes damping-off disease in young seedlings. Identification of Fusarium started at the species level based on morphological and molecular characteristics. Morphological characterization was performed based on a key specific to Fusarium spp. Whereas, molecular identification was carried out by amplification and sequencing of the regions from internal transcribed spacer (ITS) and the elongation factor using specific primers for F. circinatum. The results tasted negative implying that the suspected Fusarium is not circinatum species but, based on the results of molecular identification using universal primer pairs ITS1 (forward) and ITS4 (reverse), isolate (TZA01_DM) is identical to the fungal pathogen Fusarium sp. Sequence alignment fungal nucleotides amplified with the database at Genebank showed that, pathogenic isolate (TZA01_DM) had the closest homology of 100% with Fusarium oxysporum from France, Iran, India, Ghana and Switzerland, also has the 100% similarity index with Fusarium mundagurra (China), Fusarium concentricum (China), and Fusarium annulatum (India and Spain). The pathogenicity test was conducted through the contact of the seeds with fungal culture for 12 hrs., followed both the isolates were pathogenic to the seeds of Pinus spp., causing a reduction in the percentage of emergence and seedling damping-off. Different three fungicides were used namely Multipower Plus (78% WP), Ridomil Gold (68 WG), and Farmerzeb (80 WP), to control the mycelial growth rate of Fusarium sp in vitro and in vivo and significant results were obtained through the analysis of data using one-way ANOVA (analysis of variance) and Statistical Package for the Social Sciences (SPSS). In vitro results indicated Farmerzeb to be the best compare to the rest of the fungicides. Under in vivo germination percentage for treated and untreated controls had significant difference. Results also showed no phytotoxicity observed throughout the experiment. This is a first report in Tanzania to identify different fungi species that affect forest seeds and went further to control Fusarium obtained from such seeds through available fungicides. Moreover, the study laid the foundation for some more research to be conducted on forest seeds. The
Keyword: Fungicides, Fusarium sp, in vitro, in vivo, Pinus tecunumanii

Judul: Identification and Pathogenicity of Primary Fungi Causing Dieback Disease on Jabon Seedlings (Anthocephalus cadamba (Roxb.) Miq).
Abstrak: Jabon (Anthocephalus cadamba (Roxb.) Miq) is indigenous plant of Indonesia which is currently attracted by many people due to able provide benefits, both economical and ecological. Along with its development and cultivation, the market demand of jabon will get increase. Propagation of jabon potentially facing diseases disorders in the nursery area. This is because of available seedlings in the nursery area have the potential to be a host for the pathogens and the succulent seedling conditions are relatively vulnerable to disease attacks. The disease symptoms are often found in the jabon nursery areas and potentially leading to death of seedlings are dieback diseases. This study was conducted with the aim to isolate and identify the fungal pathogen cause of dieback diseases on jabon seedlings, determine the primary cause of dieback diseases and test the virulence levels of those isolates, and to study the mechanisms of pathogen infection and host defense mechanisms to against pathogens. The study consisted of the observation of symptoms and sampling diseased plants from the nursery locations, isolation and identification of fungi, pathogenicity assay of fungal isolates, analysis of pectinase and cellulase activities produced by fungal pathogens, and analysis of peroxidase activity on jabon. Based on observation of symptoms at the nursery sites, jabon seedlings infected dieback disease had necrotic symptoms on stems or leaves, withered or shriveled on stems. A total of 21 isolates of the fungus could be isolated from diseased plants showed necrotic symptoms at the plant tips. Identification based on morphological characters, these isolates were known as Botryodiplodia spp. as much as 9 isolates, Fusarium spp. 9 isolates, Colletotrichum sp., Curvularia sp., and Pestalotiopsis sp. each 1 isolate. Based on Koch's postulates, the fungal isolates which were pathogenic to jabon were Botryodiplodia spp., Fusarium spp., and Colletotrichum sp.. The fungus suspected as the primary cause of the dieback disease was Botryodiplodia spp. This is because of Botryodiplodia spp. isolates inoculation could produce identical symptoms with dieback symptoms that occur naturally in the field. The results of pathogenicity assay of 5 Botryodiplodia spp. isolates showed that these isolates had different degrees of pathogenicity. It could be seen from the percentage of disease severity caused. Based on Duncan's multiple interval test (α 5%) on the disease severity, could be seen that 3 of 5 Botryodiplodia spp. isolates tested were highly virulent to jabon seedlings, while the others were less virulent. The mechanisms used by Botryodiplodia spp. isolates to infect the hosts presumably performed using mechanical and biochemical forces. These were showed by the appearance of necrotic symptoms on unwounded inoculation sites and the pectinase and cellulase activities detectable from Botryodiplodia spp. isolates cultured in CMS (Corn Meal Sand) media. Pectinase activity produced by Botryodiplodia spp. isolates was ranging from 18.131 to 26.083 U ml-1, whereas cellulase from 0.014 to 0.023 U ml-1. The defense mechanism of jabon plant against pathogen infection, one of them was vii performed by produce peroxidase which plays role of lignification process and secondary metabolite compound formation. Peroxidase activity detectable on the jabon plants after pathogen inoculation was ranging from 0.0006 to 0.0012
Keyword: Botryodiplodia spp., Fusarium spp., Koch’s postulate, necrotic, nursery

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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