A Comparative Study of Four Viroids of Plants

Abstract

The host‐ranges and the reactions of particular plant hosts to inoculation with severe (s‐PSTV) and mild (m‐PSTV) strains of potato spindle tuber viroid, as well as with chrysanthemum stunt viroid (CSV) and cucumber pale fruit viroid (CPFV) were quite similar. Some minor differences did not exceed the limits of differences noted for the strains of the same plant viroid. Two‐directional crossprotection was noted for each viroid pair when s‐PSTV, m‐PSTV, CSV and CPFV were tested on chrysanthemum cv., ‘Bonnie Jean’ plants. Finally, the relative mobility of RNAs of s‐PSTV, m‐PSTV, CSV and CPFV on 5% polyacrylamide gel was identical, no matter what extraction method from plant material was used. We postulate that these four plant viroids may be regardedas the strains of the same plant viroid “species”. On the other hand, chrysanthemum chlorotic mottle viroid (ChCMV) appeared to be a quite different plant pathogen. This viroid infected and caused symptoms only in chrysanthemum plants, and was able to infect and induce symptoms on plants which had already been infected with any other viroid studied, and it did not protect chrysanthemum cv. ‘Bonnie Jean’ plants against any of the other viroids. We were not able to locate a ChCMV‐RNA band on polyacrylamide gel.

Scientific Opinion on the risk to plant health posed by Chrysanthemum stunt viroid for the EU territory, with identification and evaluation of risk reduction options

“…CChMVd has a genome composed of 398-401 nucleotides with almost no sequence similarity with CSVd and can be easily discriminated from the latter by available molecular detection methods. It has been shown that CSVd can be transmitted to tomato (Solanum lycopersicum) and potato (Solanum tuberosum), inducing symptoms similar to those caused in these hosts by other pospiviroid species, which may range from very mild to severe (Runia and Peters, 1980;Kryczynski and Paduch-Cichal, 1987;Verhoeven et al, 1998;Chung et al, 2001 (Runia and Peters, 1980). CSVd has been experimentally transmitted to at least 41 additional species in the family Asteraceae (Table 2), with macroscopic symptoms observed in only some of them.…”

“…CChMVd is outside the scope of the present PRA. Venidium fastuosum Diener, 1979 Asteraceae Verbesina encelioides Diener, 1979 Asteraceae Zinnia elegans Diener, 1979 Cucurbitaceae Benincasa cerifera Runia and Peters, 1980 Cucurbitaceae Cucumis sativus Runia and Peters, 1980 Solanaceae Petunia axillaris Runia and Peters, 1980 Solanaceae Petunia hybrida Runia and Peters, 1980 Solanaceae Petunia inflata Runia and Peters, 1980 Solanaceae Petunia nyctaginiflora Runia and Peters, 1980 Solanaceae Capscum annuum Runia and Peters, 1980 Solanaceae Nicandra physaloides Runia and Peters, 1980 Solanaceae Solanum lycopersicum Niblett et al, 1980;Verhoeven et al, 1998 Solanaceae Solanum melongena Runia and Peters, 1980 Solanaceae Solanum tuberosum Runia and Peters, 1980 -Cichal, 1987 As many plant species have never been assessed as potential hosts of CSVd, there are uncertainties about their potential host status, such that the above list is likely to be incomplete. It has been shown that CSVd can be transmitted to tomato (Solanum lycopersicum) and potato (Solanum tuberosum), inducing symptoms similar to those caused in these hosts by other pospiviroid species, which may range from very mild to severe (Runia and Peters, 1980;Kryczynski and Paduch-Cichal, 1987;Verhoeven et al, 1998;Chung et al, 2001 (Runia and Peters, 1980).…”

“…Experimental evidence indicates that CSVd may induce severe symptoms in both tomato and potato plants (Runia and Peters, 1980;Kryczynski and Paduch-Cichal, 1987;Verhoeven et al, 1998;Chung et al, 2001; Experimental evidence indicates that CSVd may induce severe symptoms in both tomato and potato plants (Runia and Peters, 1980;Kryczynski and Paduch-Cichal, 1987;Verhoeven et al, 1998;Chung et al, 2001; …”

“…However, no natural infection on these hosts has been reported so far. -Cichal, 1987 As many plant species have never been assessed as potential hosts of CSVd, there are uncertainties about their potential host status, such that the above list is likely to be incomplete.…”

“…In contrast, CSVd may elicit different symptomatic reactions in potato, ranging from a severe stunting and chlorosis to no symptoms, depending on the cultivar (Runia and Peters, 1980). Leaf deformation and grow reduction, accompanied by spindle-and doll-shaped tubers, were reported following inoculation with CSVd in experimentally infected potato plants (Kryczynski and Paduch-Cichal, 1987 (Singh, 1974;Kryczynski and Paduch-Cichal, 1987;Verhoeven et al, 1998;Chung et al, 2001; EFSA Panel on Plant Health (PLH), 2011; and J.Th.J. Verhoeven, Plant Protection Service of the Netherlands, personal communication, March 2011).…”