Judul: Yellows Disease on Carrots (Daucus carota L.) Associated with Phytoplasma in West Java.
Abstrak: Carrot (Daucus carota L.) is in the family Umbelliferae grown for its edible root. Carrots are widely cultivated in the highlands with loose soil type that rich of humus. It is an important vegetable plant in Indonesia and is widely consumed because it is rich in beta-carotene (A vitamin). Carrot cultivation in Indonesia was initially concentrated in West Java, such as in Cipanas (Bogor) and Lembang (Bandung), but currently it has spread to Central and East Java and outside Java due to its higher demand. One of the problems in carrot cultivation is pathogen infections that cause plant diseases and can potentially reduce yield quality and productivity. Diseases infecting carrot plants in Indonesia caused by viruses, bacteria, fungi and nematodes have been widely reported, but until now there have been no reported diseases caused by phytoplasma. Infection of phytoplasma has been reported to cause significant yield loss in some countries. Therefore, it is necessary to conduct research to determine the status of phytoplasma infecting carrot in Indonesia. Research was carried out with the following objectives: (1) Conducting observation and survey to confirm the presence of yellowing disease and leafhoppers in carrot growing areas in West Java; (2) Studying the morphological, histological and molecular properties of phytoplasmas associated with yellow disease in carrot in West Java; (3) Studying the potential of leafhoppers species Orosius argentatus and Balclutha incisa as the vector of yellow disease in carrot. Research activity began with a field survey on carrot plantations, followed by identification and characterization of phytoplasma in the laboratory and transmission assay of phytoplasma through leafhoppers in a screenhouse. During the survey in Bogor, Cianjur and Bandung, yellowing symptoms and the presence of leafhoppers were observed. Plant samples from the field were brought to the laboratory for identification of phytoplasma. The identification method consisted of microscopic observation using a transmission electron microscope (TEM), molecular detection using nested-polymerase chain reaction (nested-PCR), followed by cloning of phytoplasma DNA. Planthopper samples from the field were brought to the laboratory for identification based on morphological characters and the molecular identification of phytoplasmas associated with planthoppers. Furthermore, sequence analysis was carried out based on the 16S rRNA gene using the BLASTn, phylogenetic analysis, and in silico RFLP. The incidence of yellow disease in carrots is low, ranging from 6.22 - 7.87% in Bogor, 7.47% in Cianjur, and 5.97% in Bandung. Five species of leafhopper were found in carrot fields showing yellow symptoms in Bogor and Cianjur, i.e. B. incisa, Cicadulina bipunctata, Empoascanara indica, Exitianus indicus, O. argentatus and one species of planthopper, Sogatella furcifera. Molecular detection using nested-PCR confirmed the association of phytoplasma with yellow symptom in carrot and 4 planthopper species. Observations using TEM showed that there were abnormalities in the shape and integrity of cells in carrot leaf tissue with yellow symptoms compared to healthy plant cells. In addition, phytoplasma cells were found in the phloem tissue of symptomatic plant leaves with a rounded (spherical) but not fixed (pleomorphic) shape measuring about 0.2-0.5 m. Chlorophyl content of symptomatic leaves decreases 0.106%, but carbohydrate content as starch and reducing sugar
Keyword: analisis filogenetik, gen 16Sr RNA, insidensi penyakit, nested-PCR, wereng daun

Judul: Deteksi Pepper vein yellow virus (PeVYV) Penyebab Penyakit Daun Merah pada Tanaman Wortel di Jawa Barat
Abstrak: Red leaf disease (RLD) is a new reported virus disease on carrot in Indonesia. The disease was characterized by reddening of leaves without any retardation of plant development. The disease was resemble to „carrot motley dwarf (CMD)‟ reported worldwide. Although the symptom likely to be similar, these two diseases were caused by two different viruses. CMD was caused by infection of Carrot red leaf virus (Polerovirus). Whereas, RLD was induced by other Polerovirus, Pepper vein yellow virus (PeVYV). PeVYV has a narrow host range, limited on chili pepper. A report that PeVYV infect carrot in a field of Cipanas, Cianjur was the first report for the virus having host plant other than chili pepper. In this study, some surveys were conducted to elucidate the occurrence of PeVYV in carrot production centers of West Java. Some carrot plants showing RLD were collected from Cipanas (Cianjur), Lembang (West Bandung), and Cikajang (Garut). Based on reverse trancription-polymerase chain reaction analyses, it was found that PeVYV has been already occurred in the areas. The fact that all samples from Garut were infected by the virus suggest that PeVYV may first infected carrot plants in Garut, then spread to other areas of West Java. This is the first report concerning the distribution of PeVYV on carrot crops in West Java.
Keyword: RT-PCR., Production centres, Polerovirus, Distribution

Judul: Approximation of the Median of Poisson Distribution Using the Relation of Poisson-Gamma Distribution
Abstrak: A major drawback of median is that median cannot usually be defined in closed form, even in the cases where their distribution functions are known. This study gives an approximation of the closed form for the median of the Poisson distribution by using the relation of Poisson-Gamma distribution. The approximation uses elementary techniques based on the monotonicity of certain sequences involving tail probabilities of the Poisson distribution and the Central Limit Theorem. Furthermore, a closed form expression for the mean absolute deviation 􀜧|􀜰􀰒 􀵆 􀜯􀝁􀝀􁈺􀜰􀰒􁈻| is also studied. The median is relevant because of the fact that it minimizes the mean absolute deviation of a Poisson random variable (􀜰􀰒􁈻 by considering median as central tendency.
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