ISHS Acta Horticulturae 234: VII International Symposium on Virus Diseases of Ornamental Plants
REDUCED SUSCEPTIBILITY OF FLORISTS' CHRYSANTHEMUM TO ERWINIA CHRYSANTHEMI FOLLOWING VIROID INFECTION |
| Authors: | R.J. McGovern, R.K. Horst, R.S. Dickey |
| Abstract:
Prior infection of plants with certain viroids has been shown to both reduce and increase disease caused subsequently by fungal and bacterial pathogens. The objective of these investigations was to determine whether prior infection with potato spindle tuber viroid (PSTV), chrysanthemum stunt viroid (CSV), and chrysanthemum chlorotic mottle viroid (ChCMV), including a symptomless viroid (ChCMV-ns), could influence susceptibility of florists' chrysanthemum to Erwinia chrysanthemi. Rooted cuttings of viroid-free cultivar Bonnie Jean were stab-incoulated with partially purified viroid nucleic acid. Cuttings were removed from viroid infected plants and used in bacterial maceration assays at 5–10 day intervals from 10 to 60 days after viroid inoculation. Mean pith maceration by E. chrysanthemi in cuttings of chrysanthemum cv. Bonnie Jean was consistently reduced by prior infection with ChCMV-ns and by CSV. By contrast maceration was not consistently reduced by a comparable treatment with PSTV or by the symptomatic strain of chrysanthemum chlorotic mottle viroid (ChCMV-s). Interestingly, bacterial growth was neither inhibited in vitro by diffusates from CSV-, ChCMV- and PSTV-infected stem segments nor by partially purified CSV or PSTV preparations. And no difference in virulence was observed between the bacteria isolated from CSV-infected and those from CSV-free plants. Since little is known about how viroids cause disease, one may speculate that some of the cytological changes brought on by CSV infection (Morelli, et al., 1987) may be responsible in part for viroid-induced changes in susceptibility to E. chrysanthemi. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
