Reassessment of the presence of viroid species of the genus Pospiviroid in infected floral parts, using reverse transcription – polymerase chain reaction and infectivity assays

Abstract

Potato spindle tuber viroid (PSTVd) is a seed-transmissible viroid that can be present in floral parts of the host. However, a recent study (Y. Zhu, L. Green, Y.-M. Woo, R. Owens, and B. Ding. 2001. Virology, 279: 69–77), using Agrobacterium -mediated inoculation and in situ hybridization, has shown that PSTVd is present in sepals, but absent in petals, stamens, and ovary of infected tomato plants. In earlier studies, the presence of PSTVd in floral parts was determined by polyacrylamide gel electrophoresis and infectivity assays. In the present study, the presence of PSTVd and other species of the genus Pospiviroid in floral parts of tomato and other host species was studied using the highly sensitive reverse transcription – polymerase chain reaction. The reassessment showed that PSTVd was present in all floral parts of tomato, as evidenced by strong bands of polymerase chain reaction products. Moreover, floral-organ extracts containing the infectious viroid caused characteristic PSTVd symptoms in tomato seedlings. Additionally, PSTVd and Tomato chlorotic dwarf viroid (TCDVd), a viroid nontransmissible to seed, were also detected in the floral parts of Nicotiana glutinosa, in which both viroids caused characteristic colour-break symptom in petals upon infection. Species of the genus Pospiviroid were also isolated from floral parts of cultivars of infected ornamental plants of Verbena × hybrida, on one side, and Impatiens walleriana and Impatiens hawkeri, on the other side, possessing respectively two different types of petals.

Keywords:

• Potato spindle tuber viroid
• pospiviroids
• viroids
• molecular detection
• colour break
• floral parts
• tomato
• ornamental plants
• Verbena sp.
• Impatiens spp