Judul: Insidensi Penyakit Daun Keriting Kuning Cabai di Bengkulu dan Penularannya Melalui Biji
Abstrak: Penyakit daun keriting kuning merupakan salah satu penyakit penting pada cabai di Indonesia yang disebabkan oleh Pepper yellow leaf curl virus (PYLCV) yang tergolong dalam genus Begomovirus dari famili Geminiviridae. Penularan dan penyebaran PYLCV di lapangan terjadi melalui vektor serangga kutukebul Bemisia tabaci. Potensi penularan benih PYLCV telah pernah dibahas. Penelitian dilakukan untuk mengetahui insidensi penyakit keriting kuning pada cabai di Kabupaten Kepahiang, Provinsi Bengkulu dan untuk memastikan virus tidak terbawa biji cabai. Pengamatan insidensi penyakit dilakukan di Desa Sumber Sari dan Desa Tangsi Duren. Sampel daun dan buah cabai dari lapangan dibawa ke laboratorium untuk penelitian lebih lanjut. Deteksi PYLCV dari sampel daun dilakukan dengan metode polymerase chain reaction (PCR) menggunakan primer universal Begomovirus SPG 1/2 dilanjutkan dengan sekuensing DNA. Biji cabai diekstraksi dari buah yang dikumpulkan dari lapangan, kemudian ditanam di rumah kaca. Pengamatan gejala penyakit dilakukan pada masing-masing tanaman dilanjutkan dengan deteksi PCR untuk memastikan adanya infeksi PYLCV. Insidensi penyakit di lapangan sangat tinggi, berkisar antara 62,69 sampai 100%. Gejala penyakitnya bermacam-macam, dari daun menguning, daun melengkung, hingga kerdil pada seluruh tanaman. Hasil deteksi PCR menunjukkan 8 dari 12 sampel positif terinfeksi Begomovirus. Berdasarkan analisis sekuens, isolat Begomovirus asal Kepahiang memiliki homologi 89,34-98,99% terhadap Pepper yellow leaf curl Indonesia virus. Sifat penyebaran penyakit keriting kuning cabai pada benih varietas cabai di Kepahiang perlu dikonfirmasi lebih lanjut., Yellow leaf curl disease is one of the most important diseases on chili pepper in Indonesia caused by Pepper yellow leaf curl virus (PYLCV), which belongs to the genus Begomovirus of the family Geminiviridae. Transmission and distribution of PYLCV in the field occurs through the insect vector, whitefly Bemisia tabaci. The potential for seed transmission of PYLCV has been discussed previously. Research was conducted to determine the incidence of yellow leaf curl disease of chili pepper in Kepahiang Regency, Bengkulu Province and to ensure that the virus is not seed transmitted. Observation of disease incidence was carried out in Sumber Sari and Tangsi Duren villages. Leaf and chili fruit samples from the field were taken to the laboratory for further studies. PYLCV detection from leaf samples was carried out by polymerase chain reaction (PCR) method using Begomovirus SPG1/2 universal primer followed by DNA sequencing. Chili seeds were extracted from fruit collected from the field, then grown in a greenhouse. Observation of disease symptoms was carried out on each plant followed by PCR detection to confirm PYLCV infection. Disease incidence in the field was very high, ranging from 62.69 to 100%. Disease symptoms varies, from leaf yellowing, leaf curling, to stunting of the whole plant. The result of PCR detection showed that 8 out of 12 samples were positively infected with Begomovirus. Based on sequence analysis, the Begomovirus isolates from Kepahiang has 89.34 to 98.99% homology to Pepper yellow leaf curl Indonesia virus. The seedborne nature of pepper yellow leaf curl disease on chili pepper varieties in Kepahiang needs further confirmation.
Keyword: disease incidence, disease symptom, Pepper yellow leaf curl Indonesia virus, polymerase chain reaction, whitefly

Judul: Response of Several Chili Accessions and Molecular Markers to Yellow Leaf Curl Disease
Abstrak: Penyakit daun keriting kuning merupakan penyakit penting tanaman cabai dan menjadi kendala utama dalam produksi cabai. Penyakit ini disebabkan oleh Pepper yellow leaf curl virus (PYLCV) dan ditularkan oleh serangga vektor kutukebul Bemisia tabaci (Hemiptera: Aleyrodidae). Penggunaan varietas tahan direkomendasikan sebagai salah satu cara pengendalian penyakit, tetapi belum tersedia varietas cabai tahan PYLCV secara komersial. Penelitian ini dilakukan untuk mengevaluasi ketahanan 10 aksesi cabai koleksi Balai Besar Penelitian Bioteknologi dan Sumberdaya Genetik Pertanian (BBBiogen) dan mengidentifikasi marka molekuler yang berhubungan dengan sifat ketahanan cabai terhadap PYLCV. Tanaman cabai uji berumur 30 hari setelah tanam diinokulasi PYLCV menggunakan kutukebul dengan periode makan akuisisi dan inokulasi masing-masing 48 jam, dengan 10 ekor kutukebul per tanaman. Respons tanaman diamati berdasarkan gejala, insidensi dan keparahan penyakit. Konfirmasi infeksi PYLCV pada tanaman uji dilakukan dengan metode deteksi polymerase chain reaction (PCR) menggunakan primer universal Begomovirus. Gejala penyakit pada tanaman cabai uji meliputi daun menguning, tulang daun menebal serta memucat, serta tanaman kerdil. Insidensi dan keparahan penyakit pada tanaman cabai uji berturut-turut berkisar 0-36% dan 0-28%; sedangkan pada tanaman kontrol rentan PYLCV, yaitu varietas Bara berturut-turut 88% dan 61%. Delapan dari 10 galur cabai uji menunjukkan respons tahan terhadap PYLCV. Pola polimorfisme pada galur cabai uji diperoleh dengan marka CaBR61 dan CaBR98, walaupun dua marka tersebut tidak dapat digunakan sebagai penanda respons ketahanan terhadap PYLCV., Yellow leaf curl disease is an important disease of chili plants and a major obstacle to chili production. This disease is caused by Pepper yellow leaf curl virus (PYLCV) and is transmitted by the whitefly vector Bemisia tabaci (Hemiptera: Aleyrodidae). The use of resistant varieties is recommended for controlling this disease, but there are no commercially resistant PYLCV varieties available. This study was conducted to evaluate the resistance of 10 chili accessions from the collection of Balai Besar Penelitian Bioteknologi dan Sumberdaya Genetik Pertanian (BBBiogen) and to identify molecular markers associated with chili resistance to PYLCV. Thirty days-old chili plants were inoculated with PYLCV using whitefly with acquisition and inoculation feeding periods of 48 hours each, and 10 whiteflies per plant. Plant response was observed based on symptoms, incidence, and severity of the disease. Confirmation of PYLCV infection in the test plants was carried out by polymerase chain reaction (PCR) detection method using Begomovirus universal primer. Symptoms of the disease in the tested chili plants include leaf yellowing, thickening and blanching of leaf veins, and stunting of the plants. Incidence and severity of the disease in the tested chili plants ranged from 0-36% and 0-28%, respectively; whereas in control plants susceptible to PYLCV, i.e., var. Bara was 88% and 61%, respectively. Eight of the 10 tested chili accessions showed resistant response to PYLCV. Polymorphism patterns in chili accessions were obtained with CaBR61 and CaBR98 markers, although these two markers cannot be used as markers for resistance response to PYLCV.
Keyword: disease incidence, molecular marker, polymorphism, polymerase chain reaction, whitefly

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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