First report of Tomato chlorotic dwarf viroid in Mexico
At the beginning of 2008, tomato plants (Lycopersicon esculentum) grown in a large glasshouse near Mexico city (Mexico) showed general stunting, leaf chlorosis which later turned bronze or purple, and fruit size reduction. The disease was initially confined to a 5 ha glasshouse but it quickly spread to 2 additional 5 ha glasshouses during summer 2008. By the end of 2008, approximately 5 % of tomato plants in 35 ha of glasshouses were infected. Samples were collected (12 in 2008 and 4 in 2009) from diseased tomato plants and tested. Samples tested negative for common tomato viruses but gave positive results when tested with specific primers for pospiviroids. In 2 samples, sequence analysis indicated a mixed infection with 2 pospiviroids: Tomato chlorotic dwarf viroid (TCDVd) and a viroid closely related to Mexican papita viroid*. In addition, the Mexican isolate of TCDVd was 99% identical to an isolate recently identified in Arizona, USA (EPPO RS 2008/006).
The close relationships between the Mexican and US isolates suggest that TCDVd in these two countries may share a common origin, and it is hypothetized that they might have been introduced with infected tomato seeds. This is the first time that Tomato chlorotic dwarf viroid is reported from Mexico.
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* Mexican papita viroid was first identified in Mexico in 1996 on papita (Solanum cardiophyllum).
Sources
Ling KS, Zhang W (2009) First report of a natural infection by Mexican papita viroid and Tomato chlorotic dwarf viroid on greenhouse tomatoes in Mexico. Plant Disease 93(11), p 1216.