Pathology and properties of tulip virus X, a new potexvirus

SUMMARY Tulip virus X (TVX), a previously undescribed mechanically transmissible virus, causes chlorotic and necrotic lesions in leaves and streaks of intensified pigmentation in tepals of tulip plants. The virus infected 22 of 42 other plant species in 10 of 14 families, but most host species were infected only erratically. TVX is best propagated in Chenopodium quinoa and assayed in C. amaranticolor . Spindleshaped inclusions were observed in epidermal cells of C. amaranticolor leaves. Leaf extracts from C. quinoa contained flexuous filamentous particles measuring c. 495 ×13 nm. The extracts were infective after dilution to 10 ‐9 , after heating for 10 min at 60 °C but not at 65 °C, and after storage at c. 20 °C for 30 days or at ‐20 °C for 6 months. TVX particles were purified (500 μg/g C. quinoa leaf) from tissue extracts in 0.067 M phosphate buffer containing 10 mM EDTA at pH 7, by twice precipitating the virus with 8% polyethylene glycol in 0.2 M NaCl followed by differential centrifugation. The virus particles have a sedimentation coefficient ( s 20, w ) of 102 S. They contain a protein of mol. wt c. 22 500 and a nucleic acid that, when glyoxalated, migrates in agarose gel like single‐stranded RNA of mol. wt 2.05 × 10 6 . TVX particles tend to aggregate, and evidence was obtained that a 118 S component which was consistently observed in purified preparations and in infective sap is an end‐to‐end dimer. A distant serological relationship was found between particles of TVX and those of viola mottle and hydrangea ringspot viruses, but no serological relationship was detected to nine other potexviruses. TVX is considered to be a distinct and definitive member of the potexvirus group.