Penyakit virus tular umbi merupakan salah satu kendala dalam meningkatkan produksi bawang merah. Hal ini disebabkan oleh virus yang infeksinya bersifat sistemik. Apabila partikel virus berada dalam jaringan benih umbi, maka akan sulit untuk dikendalikan dan dapat membawa masalah baru pada pertanaman berikutnya. Penelitian bertujuan mengetahui insiden penyakit virus tular umbi pada 13 varietas bawang merah yang berasal dari Jawa Barat dan Jawa Tengah. Penelitian dilaksanakan di Rancaekek (elevasi 650 m dpl.) dan di Laboratorium Balai Penelitian Tanaman Sayuran Lembang (elevasi 1.250 m dpl.), sejak bulan Agustus sampai November 2004. Perlakuan terdiri atas 13 varietas bawang merah, yaitu: Lodra, Sumenep, Batu, Merah Maja, Merah Cigugur, Ciniru, Bima, Bima Curut, Bima Timor, Bima Arjuna, Kuning Tablet, Kuning Gombong, dan Philipina. Rancangan yang digunakan ialah acak kelompok dengan tiga ulangan. Hasil penelitian menunjukkan bahwa (1) insiden penyakit virus tular umbi pada masing-masing varietas bawang merah asal Jawa Barat dan Jawa Tengah berturut-turut yaitu varietas Lodra 84,67%, Sumenep 82,56-100%, Batu 39,86-78,67%, Merah Maja 95,25%, Merah Cigugur 100%, Ciniru 66,27%, Bima Curut 78,57%, Bima 100%, Bima Timor 57,98%, Bima Arjuna 47,96%, Kuning Tablet 57,48%, Kuning Gombong 97,92%, dan Philipina 97,92 %, (2) gejala infeksi virus pada daun umumnya berupa  klorosis, mosaik bergaris kuning vertikal terputus-putus, garis-garis hijau vertikal, dan ukuran daun menjadi kecil, (3) gejala-gejala tersebut bereaksi positif dengan OYDV(onion yellow dwarf virus) dan SYSV (shallot yellow stripe virus) berdasarkan uji DAS-ELISA (double antibody sandwich-enzyme linked immunosorbent assay). Informasi mengenai insiden virus tular umbi pada bawang merah ini sangat penting dalam rangka mengembangkan metode perbenihan bawang merah bebas virus. <br /><br />Virus disease is one of major problems in increasing shallots production, because its infection has a systemic character. If it is already in shallots bulb tissues, the virus is difficult to be controlled and will cause new problems to the next planting. The experiment was aimed to determine incidence of bulb-borne virus diseases on  thirteen varieties of shallots (Allium cepa var. ascalonicum) originated from West  and Central Java. The experiment was carried out at Indonesian Vegetable Research Institute Lembang (1,250 m asl.) and Rancaekek (650 m asl.), from  August to November 2004. The shallot varieties tested were Lodra, Sumenep, Batu, Merah Maja, Merah Cigugur, Ciniru, Bima, Bima Curut, Bima Timor, Bima Arjuna, Kuning Tablet, Kuning Gombong, and Philipina. A randomized complete block design with three replications were used in this experiment. The results of the experiment showed that  (1) incidence of virus diseases in shallots bulb on variety Lodra was 84.67%, Sumenep 82.56-100%, Batu 39.86-78.67%, Merah Maja 95.25%, Merah Cigugur 100%, Ciniru 66.27%, Bima Curut 78.57%, Bima 100%, Bima Timor 57.98%, Bima Arjuna 47.96%, Kuning Tablet 57.48%, Kuning Gombong 97.92%,  and Philipina 97.92 %, (2) the virus symptoms exhibited on infected shallots were  yellow stripe mosaic, chlorosis,  green stripe leaf,  and leaves became small, and (3) the symptoms were associated with OYDV (onion yellow dwarf virus) and SYSV (shallots yellow stripe virus) base on DAS-ELISA (double antibody sandwich-enzyme linked immunosorbent assay). Information on the incidence of viral diseases on shallots bulb is very important to develop the production technology of virus-free shallots bulb.<br /><br /><br />

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SUMMARYCucumber mosaic virus (CMV) strain Y from Japan was propagated in Xanthi tobacco. Virus isolated from four successive passages was analysed for its constituent RNAs by polyacrylamide gel electrophoresis (PAGE) under semi-denaturing and fully denaturing conditions. This revealed the initial presence of the 368-nucleotide satellite RNA Y-CARNA 5 (for Y-CMV-associated RNA 5) and the subsequent emergence of a small RNA in the 335-nucleotide size range, which we termed Yn-CARNA 5.