CHARACTERIZATION OF A POTYVIRUS CAUSING MILD MOSAIC ON TUBEROSE

A virus inducing mild mosaic symptoms on the leaves and peduncles of t uberose (Polianthes tuberosa) was isolated and partially characterized . The isolate, designated Tbr1, could be transmitted mechanically and by green peach aphids (Myzus persicae) in a non-persistent manner to t uberose seedlings but not to 16 common assay species. Flexuous rod-sha ped particles with a mean length of 750 nm could be easily seen in inf ected leaf dips and in purified samples. Cytoplasmic cylindrical inclu sions, pinwheel and laminated aggregates similar to those assigned to potyviral cylindrical inclusion type II, were observed in infected tub erose leaves. The purified capsid contained a single species of protei n monomer with an estimated relative mass of 38 kDa. In reciprocal sod ium dodecyl sulfate-immunodiffusion tests, antiserum against Tbr1 reac ted only with its homologous antigen but not with 22 different known p otyviruses. Using primer pairs designed for potyvirus sequence amplifi cation, a 2-kb DNA product equivalent to the estimated size for potyvi ruses was consistently amplified from purified Tbr1 virions or from cr ude infected tissue by reverse transcription polymerase chain reaction . On the basis of these results, Tbr1 was recognized as a unique speci es in the genus Potyvirus and hence designated as tuberose mild mosaic potyvirus (TMMV).