First report of natural infection of greenhouse tomatoes by potato spindle tuber viroid in the United States

Authors: Ling, Kai-Shu; SFETCU, DANA - Houweling Nurseries Oxnard, Inc

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/24/2010
Publication Date: 11/1/2010
Citation: Ling, K., Sfetcu, D. 2010. First report of natural infection of greenhouse tomatoes by potato spindle tuber viroid in the United States. Plant Disease. 94(11):1376.

Interpretive Summary: In early 2009, a large number of tomato plants in a commercial greenhouse tomato facility in Southern California suffered from a serious chlorotic stunting disease that is different from a typical Pepino mosaic virus (PepMV) infection (mosaic, yellow patches on leaves and marbling fruits). The disease was initially localized in certain areas in a greenhouse, but had since spread to neighboring greenhouses in 2010. The disease resulted in a significant yield loss due to the production of reduced fruit size. Upon screening with a panel of common tomato viruses and viroids, a pospiviroid-specific polymerase chain reaction (PCR) product was consistently associated with the disease, frequently in mixed infection with PepMV. Upon genome sequencing and analysis, it was determined that this pospiviroid was Potato spindle tuber viroid (PSTVd). PSTVd is the causal agent for a serious spindle tuber disease in potatoes and has also been identified in a number of ornamental plants in the U.S. Although PSTVd has been identified to infect greenhouse tomatoes in Europe and New Zealand, this is the first time it is identified in a natural infection of tomatoes in the U.S. This highly contagious disease poses a major threat to the $400 million greenhouse tomato industry in the U.S.

Technical Abstract: In early 2009, a large number of tomato plants (Solanum lycopersicum L.) grown in a commercial greenhouse facility located in Southern California exhibited general plant stunting, leaf chlorosis and spindly shoots. The disease resulted in a significant yield loss due to the production of reduced fruit size. The disease was initially localized in certain areas in a greenhouse, but had since spread to neighboring greenhouses in 2010. Upon screening with a panel of common tomato viruses and viroids, a pospiviroid-specific RT-PCR product was consistently identified in the symptomatic plants but not in the healthy-looking individuals. Subsequently, full viroid genomic sequences were obtained through RT-PCR using primer specific for Potato spindle tuber viroid (PSTVd) as well as for pospiviroid genus. Sequences obtained from direct sequencing of amplicons or cloned PCR products were identical and consisted of a full viroid genome of 358 nt which was named PSTVd-CA1. BLASTN queries of the NCBI database showed that this isolate had a high sequence identity (98%) to other PSTVd isolates. The disease was reproducible upon mechanical transmission on tomato ‘Moneymaker’ and PSTVd was recovered from the inoculated tomato plants. Natural PSTVd infection on greenhouse tomatoes has been reported in Europe and New Zealand. Although a number of reports in the U.S. have been published on naturally-occurring PSTVd infection of potatoes, to our knowledge, this is the first report of a natural PSTVd infection on tomatoes in the U. S.