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چکیده
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Grapevine (Vitis vinifera) hosts many viruses and at least five viroids, Grapevine yellow speckle viroid 1 (GYSVd-1), Grapevine yellow speckle viroid 2 (GYSVd-2), Australian grapevine viroid (AGVd), Hop stunt viroid (HSVd) and Citrus exocortis viroid (CEVd). Although infections by most of these viroids are latent, “yellow speckle” symptoms can be induced in the leaves by GYSVd-2 and/or GYSV-1 alone. The association of these viroids with the nepovirus Grapevine fanleaf virus (GFLV) is reported to elicit a syndrome denoted “vein banding”. Here, we report the results of a survey of grapevine viroids, GFLV and Arabis mosaic virus (ArMV) conducted in north-west Iran during summer 2010. Nucleic acids, extracted from the leaves of 137 grapevines, were first tested using a multiplex RT-PCR protocol developed for the simultaneous detection of the five viroids. Of these samples, 64%, 91%, 95%, and 100%, were infected by GYSVd-2, GYSVd-1, AGVd and HSVd, respectively. Combinations of three and four different viroids were found in most plants (88%), with the exclusion of CEVd, which was not detected in any of the vines. When the same extracts were further tested by single RT-PCR for GFLV and ArMV, GFLV was detected in 37% of the samples, whereas ArMV was totally absent. “Yellow speckle” symptoms, observed in 10% of the tested vines, were associated with the contemporary presence of GYSVd-1 and GYSVd-2, but not of GFLV. In contrast, “vein banding”, observed in 22 vines, was associated with the contemporary presence of GYSVd-1, GYSVd-2 and GFLV, thus confirming previous reports on the concurrence of different agents in the etiology of this syndrome. Data on the molecular characterization of several grapevine viroid isolates from Iran will also be presented.
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