Judul: Identification of Viruses Cause Pineapple Mealybug Wilt Disease on Pineapple Clone 7350 and Clone MD2 in Blitar Regency, East Java
Abstrak: Nanas (Ananas comosus L. Merr) merupakan salah satu komoditas ekspor penting di Indonesia. Namun, produksinya terkendala oleh infeksi patogen, termasuk virus. Baru-baru ini, survei lapangan di area produksi nanas di Kabupaten Blitar menemukan gejala mirip infeksi virus seperti daun kemerahan bercampur dengan klorosis dan ujung daun nekrotik dengan kejadian hingga 50% pada klon 7350. Penyakit ini telah diketahui menginfeksi nanas. Namun sampai saat ini identitas genetik virus penyebab penyakit layu mealybug di Indonesia masih terbatas. Penelitian bertujuan untuk mendeteksi dan mengidentifikasi spesies virus yang berasosiasi dengan penyakit layu nanas di Kabupaten Blitar. Total RNA diekstraksi dan dideteksi dengan One-Step RT-PCR menggunakan primer universal Ampelovirus, primer spesifik dari pineapple mealybug wilt-associated virus (PMWaV) 1 dan 2. Sampel positif kemudian dikonfirmasi dengan analisis runutan nukleotida. PMWaV-1 dan -2 berhasil diamplifikasimenggunakan primer spesifik pada klon 7350 dan tidak ada sampel yang terdeteksi menggunakan primer universal Ampelovirus. Di sisi lain, semua pasang primer tidak mendeteksi virus target pada klon MD2, menunjukkan gejala klorosis mungkin disebabkan oleh patogen lain. Urutan parsial gen HSP70 mengkonfirmasi keberadaan kedua spesies virus. Isolat PMWaV-1 Blitar memiliki kesamaan tertinggi (100%) nukleotida dan asam amino dengan isolat dari Taiwan dan Meksiko. Selain itu, isolat PMWaV-2 Blitar menunjukkan homologi masing-masing 99% dan 100% untuk kesamaan nukleotida dan asam amino, dengan isolat dari Taiwan, Mauritius, Kuba, dan Ghana. Hasil dari penelitian ini memastikan adanya dua spesies virus (PMWaV-1 dan -2) yang menyebabkan penyakit layu mealybug., Pineapple (Ananas comosus L. Merr) is one of the essential export commodities in Indonesia. However, virus infection causes significant yield loss. Current field survey at a pineapple production area in Blitar Regency found virus-like infection symptoms such as leaf reddish intermingle with chlorosis and necrotic leaf tips on clone 7350 and MD2 with incidence 50% and 3%, respectively. To date, there was still few information of viruses infecting pineapple in Indonesia. The aim of this study is to identify the virus species associated with mealybug wilt pineapple disease in Blitar Regency. Total RNA was extracted then detected through one-step RT-PCR method using three primer sets, including a universal primer of Ampelovirus and two specific primer pairs (PMWaV-1 and -2). Positive samples then were confirmed by nucleotide sequencing. The PMWaV-1 and PMWaV-2 were successfully amplified using specific primers on clone 7350 and there were no samples detected using Ampelovirus universal primers. In the other hand, all the primer sets did not detect any virus target on clone MD2, indicating chlorosis symptom might be caused by other pathogens. Partial sequences of the HSP70 gene confirmed the existence of both virus species. The PMWaV-1 Blitar isolates shared the highest similarities (100%) of nucleotide and amino acid with isolates from Taiwan and Mexico, respectively. Moreover, the PMWaV-2 Blitar isolates shared 99% and 100% similarities of nucleotide and amino acid, respectively with isolates form Taiwan, Mauritius, Cuba, and Ghana. The finding of this study confirmed the existence of two viruses (PMWaV-1 and -2) causing pineapple mealybug wilt disease.
Keyword: Ampelovirus, Ananas comosus, HSP70, PMWaV, RT-PCR

Judul: Distribution Pattern and the Effect of Mealybug  Wilt Virus on Four Pineapple Clone’s Rooting
Abstrak: Nanas (Ananas comosus [L.] Merr.) merupakan salah satu komoditas ekspor Indonesia. Penyakit layu mealybug yang disebabkan oleh Pineapple mealybug wilt associated virus (PMWaV) ditularkan oleh Dysmicoccus brevipes dan D. neobrevipes menjadi masalah serius dalam budi daya nanas di seluruh dunia, termasuk Indonesia. Penelitian bertujuan mempelajari insidensi penyakit, pola sebaran, dan pengaruh penyakit layu mealybug terhadap kondisi perakaran pada tanaman nanas. Parameter yang diamati yaitu tipe gejala, insidensi penyakit, pola sebaran, dan pengaruh PMWaV terhadap kondisi akar. Berdasarkan hasil penelitian, gejala PLM pada klon GP3, GP4, dan HC cukup mirip, seperti ujung daun nekrotik, daun memerah, daun melengkung ke bawah, dan layu, sedangkan pada MD2 adalah daun menguning, daun melengkung ke bawah, dan ujung daun mati. Insidensi PLM pada klon GP3, GP4, HC, dan MD2 berturut-turut adalah 0,13%, 0,27%, 0,42%, dan 0,54%. Insidensi yang tinggi pada klon HC dan MD2 berada di atas batas kendali perusahaan sehingga dikategorikan sebagai klon nanas yang rentan. Pola sebaran pada klon GP3 yaitu mengelompok, sedangkan klon GP4, HC, dan MD2 yaitu seragam. Penyakit layu mealybug berpengaruh nyata terhadap penurunan total akar dan berat basah akar, sedangkan panjang akar dan berat kering akar tidak berbeda nyata dibandingkan dengan tanaman sehat., Pineapple (Ananas comosus [L] Merr.) is one of improtant export commodities in Indonesia. However, Pineapple wilt disease (PWD) is serious problem in pineapple cultivation worldwide, including Indonesia. The study aimed to determine the distribution pattern and the effect of PMWaV infection on four pineapple clones rooting. The observation aspect including the type of symptoms, incidence of mealybug wilt disease as well as clone resistance, distribution patterns and the effect PMWaV infection on roots. Pineapple wilt symptom on clone HC, GP3, and GP4 are quite similiar, such as leaf reddening, necrotic leaf tips, down ward leaf curve, and wilt, while on clone MD2 are yellow spots, downward leaf curve, and necrotic leaf tips. The incidence of pineapple wilt on clone MD2, HC, GP4, and GP3 were 0,54%, 0,42%, 0,27%, and 0,13% respectively. The disease incidence of clone MD2 and HC was higher than company’s control thershold, indicating both clones were categorized as susceptible clones. The distribution pattern of GP3 clones is clustered, while on GP4, HC, and MD2 clones are uniform. Pineapple wilt disease affected significantly on lower total number and wet root weight, while root length and dry root weight were not significantly different compared to healthy plants.
Keyword: klon nanas, Pineapple mealybug wilt associated virus (PMWaV), penyakit layu mealybug, pola sebaran

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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