ISHS Acta Horticulturae 110: V International Symposium on Virus diseases of Ornamental Plants
BIOLOGICAL AND BIOCHEMICAL RELATIONSHIPS AMONG VIROIDS IN ORNAMENTAL PLANTS |
| Author: | R.K. Horst |
| Abstract:
Viroids are known to be the smallest microorganism to cause disease in plants. Despite the small size of viroids, a wide variety of host plants are affected by the nine different viroids which have been described. Several viroids infect the same hosts and cause similar symptoms in these hosts. For example, potato spindle tuber viroid (PSTV), citrus exocortis viroid (CEV), chrysanthemum stunt viroid (CSV) and cucumber pale fruit viroid (CPFV) infect 'Rutgers' tomato. Likewise, PSTV, CEV and CSV infect Gynura aurantiaca. In addition, we now know that Chrysanthemum morifolium is susceptible to PSTV, CEV, CSV and chrysanthemum chlorotic mottle viroid (ChCMV) and that it is biologically possible to differentiate these viroids and their strains in this host based on different symptoms produced after infection. Although viroids have been shown to differ significantly in their nucleotide sequence, the phenomenon of cross-protection is known to occur in some viroid double infections. We have now determined that PSTV, and CSV protect against CEV. In addition we have a symptomless strain of ChCMV which protects against the severe strain of ChCMV. However, ChCMV did not protect against PSTV, CEV or CSV nor did PSTV protect against ChCMV. Moreover, CSV protects against ChCMV and in the reciprocal experiments no protection of any kind was observed. This is the first documented case of non-reciprocal abilities of viroids to cross-protect. We have also found interference between viroids and bacteria in double infections in chrysanthemums. This reaction differs from the cross-protection phenomenon which involves closely related organisms (i.e., strains of a single virus and viroid). | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
