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Title: Research toward integrate management of the emerging viroid disease on tomato through seed health test, disinfectant application and disease resistance

item Ling, Kai-Shu
item Li, Rugang

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/25/2014
Publication Date: 11/4/2014
Citation: Ling, K., Li, R. 2014. Research toward integrate management of the emerging viroid disease on tomato through seed health test, disinfectant application and disease resistance. 29th Annual Tomato Disease Workshop. p 17.

Interpretive Summary: N/A

Technical Abstract: In the last few years, several devastating viroid disease outbreaks were identified on greenhouse tomatoes in North America. These emerging diseases have caused serious concerns to the tomato industry and seed suppliers. Several closely related viroid species, including Potato spindle tuber viroid (PSTVd), Tomato chlorotic dwarf viroid (TCDVd) and Mexican papita viroid (MPVd) were identified. Despite improvements in molecular detection (RT-PCR and real-time qRT-PCR) to tomato-infecting viroids in the genus Pospiviroid, accurate disease diagnosis is still not easy due to the low viroid titer in infected tissue and sequence diversity among these viroids. An integrative strategy on disease management, including seed health test, disinfectant application, and breeding for resistance should be considered. Using real-time qRT-PCR technology in seed health test and through trace back and disposition of the source of initial inoculum, a PSTVd contamination on breeding stock seeds was controlled and eradicated in a tomato breeding program. In a second scenario to manage viroid disease from further dissemination and spread in a tomato greenhouse through mechanical transmission, over 17 disinfectants were screened against PSTVd. Several disinfectants including 10% Clorox bleach, 2% Virkon were shown to be effective. However, for long term disease management, a tomato cultivar with resistance would be the most desirable to manage this emerging viroid disease. To assess genetic resistance to PSTVd, we screened 100 accessions of core tomato genetic collections through mechanical inoculation in a containment greenhouse. These germplasm included 1 Solanum arcanum, 17 S. chilense, 5 S. corneliomulleri, 27 S. habrochaites, 20 S. lycopersicum, 2 S. huaylasense, 24 S. peruvianum, and 4 S. pimpinellifolium. Evaluation of disease resistance was conducted with symptom observation and confirmation using qRT-PCR. All inoculated tomato plants in the control (S. lycopersicum ‘Rutgers’) as well as accessions listed above from S. Arcanum, S. corneliomulleri, S. lycopersicum, S. huaylasense and S. pimpinellifolium were infected by PSTVd. However, seven accessions in S. chilense (4), S. habrochaites (2) and S. peruvianum (1) had positive infection in less than 40% of inoculated plants suggesting possible resistance to PSTVd in these materials. Secondary test on cuttings from these putative resistant plants are underway to confirm their status of resistance and their results will be discussed.