Judul: Karakterisasi beberapa genotipe cabai (Capsicum spp.) dan mekanisme ketahanannya terhadap begomovirus penyebab penyakit daun keriting kuning
Abstrak: The plant breeding program to develop resistant plants of Begomovirus is needed to characterize of pepper germplasm. The activities followed by study on resistance mechanism based on information of structural and biochemical resistance against Begomovirus and their vector Bemisia tabaci. Pepper yellow leaf curl virus (PYLCV) belongs to the genus of Begomovirus, the family members of Geminiviridae. The virus has been reported as the causal agent of yellow leaf curl disease in pepper and transmitted by an insect vector, B. tabaci Genn. Evaluation of genotypes characters showed that the morphological characters of leaves, stems, flowers, and fruits can be distinguished among the genotypes of pepper. There are significant differences among pepper genotypes for the following variables: height of dicotomous, plant height, canopy width, stem diameter, leaves length and width, and flowering times. Dendrogram analysis based on qualitative characters involving 29 genotypes classifies the genotypes into 4 different groups. Most of the genotypes belong to group I, genotypes IPB C15 and IPB C63 are in group II, IPB C12 genotype in group III, whereas IPB C20 and IPB C21 are in group IV. All genotypes are included in C. annuum, except IPB C63 genotype which belongs to C. frutescens. Capsicum species differs in the form of leaves, number of flowers at per node, the position of flowers, fruit color intermediate, and plants canopy. Resistance response of the genotypes was identified based on the measurement of disease intensity. IPB C12 genotype is resistant; IPB C10 and IPB C14 genotypes are moderately resistant; IPB C15, IPB C26, and 35C2 genotypes are susceptible. PYLCV detection using PCR technique has successfully amplified 780 bp-sized Begomovirus-specific DNA fragments. Dot blot hybridization is capable to detect PYLCV in resistant and moderately resistant genotypes to a dilution level of 1: 10, whereas susceptible genotypes can reach up to 1: 100 dilution level. Susceptible genotype tended to have a Begomovirus concentrations higher than genotypes resistant or moderate resistant. Genotypes resistance to Begomovirus is associated with structure of plants i.e. density of trichome and arrangement of palisade cells. An increased accumulation of salicylic acid and peroxidase enzyme activity are detected in Begomovirus-inoculated plants, 120 hours after inoculation. Based on the correlation among characters in pepper genotypes, it can be concluded that there is a correlation between the mechanisms of structural and biochemical resistance of plants following Begomovirus infection. Longer palisade cells will lead to thicker leaf and more accumulation of salicylic acid. Trichome density and palisade cells position are the structural barrier in the mechanism of pepper resistance to B. tabaci. Resistance mechanism to Begomovirus is the result of the width of palisade cells, increased accumulation of salicylic acid, and increased activity of peroxidase enzymes. There is a correlation between the structural and biochemical mechanisms to Begomovirus, with a positive correlation between the lengths of palisade cells and salicylic acid accumulation.
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Judul: Morphological Diversity and Resistance of Various Species of Chili Pepper (Capsicum spp.) to Pepper Yellow Leaf Curl Disease
Abstrak: Masyarakat dunia telah menjadikan cabai (Capsicum spp.) sebagai salah satu komoditas hortikultura yang penting dalam penggunaannya di berbagai aspek kehidupan. Peningkatan produktivitas cabai umumnya menghadapi beberapa hambatan, salah satunya adalah serangan hama dan penyakit tanaman. Penyakit daun keriting kuning (Pepper Yellow Leaf Curl Disease/PYLCD) dapat menyebabkan kerusakan dan kehilangan hasil yang tinggi. Penyakit ini disebabkan oleh Pepper yellow leaf curl virus (PYLCV) dan ditularkan melalui serangga vektor kutu kebul (Bemisia tabaci). Pengendalian PYLCD hingga saat ini masih terbatas pada pengendalian serangga vektor. Penggunaan varietas tahan menjadi cara yang lebih efektif untuk mencegah kerusakan akibat PYLCD. Penelitian ini terdiri atas dua kegiatan utama yakni (1) karakterisasi keragaan morfologi dan agronomi serta (2) pengujian respons ketahanan 29 genotipe cabai terhadap penyakit daun keriting kuning. Percobaan pertama bertujuan untuk mendapatkan informasi keragaan karakter agronomi dan morfologi genotipe cabai yang berasal dari 4 spesies berbeda. Pengujian dilakukan di dalam rumah kaca dan dilaksanakan menggunakan rancangan kelompok lengkap teracak (RKLT) satu faktor dengan tiga ulangan. Pengamatan karakter morfologi dan agronomi dilakukan pada 32 karakter meliputi karakter kecambah, daun, batang, bunga, buah, biji dan produktivitas tanaman. Pengamatan karakter didasarkan pada panduan deskripsi cabai IPGRI. Hasil pengamatan menunjukkan adanya keragaman karakter yang cukup besar di antara genotipe uji. Genotipe uji teramati memiliki tinggi yang beragam berkisar dari tanaman yang pendek, sedang, tinggi hingga sangat tinggi. Bentuk serta ukuran tanaman cukup beragam dengan produktivitas berkisar antara 29,23 g hingga 207,92 g buah per tanaman. Percobaan kedua bertujuan untuk mendapatkan informasi respons serta kategori tingkat ketahanan tanaman terhadap penyakit daun keriting kuning. Percobaan dilakukan menggunakan dua unit percobaan yakni (1) penanaman pada kondisi bebas virus (kontrol) dan (2) penanaman pada kondisi terinfeksi virus. Inokulasi virus dilakukan dengan metode inokulasi individu menggunakan serangga vektor kutu kebul. Pengamatan meliputi karakter morfologi dan agronomi serta karakter ketahanan (periode inkubasi, tingkat insidensi dan tingkat keparahan penyakit). Tingkat ketahanan tanaman dikategorikan menjadi lima kategori berdasarkan tingkat keparahan penyakit, yakni sangat rentan, rentan, agak rentan, agak tahan dan tahan. Genotipe Adelina, Red Habanero, Red Chupetinho, F6-074, Jolokia, Fatali, F5-012328-6-2-1, Anies, F4-012328-1AB-3, F5-012328-1AB-2-1, Caman, IPBC3, dan IPBC290 termasuk kategori tanaman tahan. Genotipe F1 Baja, Seloka, Bonita, IPBC12, F4-012328-3-3, Ungara, F5-012328-6-2-2, IPBC15, dan Cakra Putih merupakan tanaman agak tahan. Genotipe Taruna dan IPBC333 termasuk dalam kategori tanaman agak rentan. Genotipe SSP, Bishop Crown dan IPB C5 termasuk dalam kategori tanaman rentan. Genotipe Yuni dan Lemon Drop termasuk kategori tanaman yang sangat rentan terhadap penyakit daun keriting kuning. Hasil pengamatan juga menunjukkan adanya perbedaan keragaan tanaman antara tanaman yang terinfeksi PYLCV dibandingkan dengan tanaman bebas virus (kontrol). Tanaman teramati mengalami penyusutan ukuran daun, dan tinggi tanaman, penyusutan ukuran buah, serta penurunan jumlah buah dan bobot buah per tanaman. Nilai penurunan tersebut diketahui berkorelasi dengan tingkat keparahan penyakit. Tanaman dengan tingkat keparahan penyakit yang lebih besar, cenderung mengalami penurunan keragaan yang lebih besar. Korelasi juga teramati antara tingkat keparahan penyakit dengan umur berbunga tanaman. Tanaman dengan tingkat keparahan penyakit yang lebih berat cenderung berbunga lebih cepat dibandingkan tanaman yang bergejala ringan. Berdasarkan kategori tingkat ketahanan dan karakter lain seperti produktivitas, masing-masing spesies cabai yang diuji memiliki genotipe unggul yang berpotensi untuk
Keyword: Begomovirus, characterization, correlation, interspecies, pepper yellow leaf curl disease

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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