Frequencies of Seed Infection and Transmission to Seedlings by Potato Spindle Tuber Viroid (A Pospiviroid) in Tomato

H. E. Simmons, Iowa State University
T. B. Ruchti, Iowa State University
Gary P. Munkvold, Iowa State University

This article is from Journal of Plant Pathology & Microbiology 6 (2015): 275, doi:10.4172/2157- 7471.1000275. Posted with permission.


Potato spindle tuber viroid (PSTVd) is an emerging pathogen that primarily affects members of the Solanaceae. The distribution of this pathogen is expanding rapidly with several countries reporting new infections in recent years. This pathogen is of phytosanitary concern because infected seed is thought to be one of the factors contributing to the spread of this disease. Thus we developed a qRT-PCR method to determine the seed infection frequency of PSTVd in tomato, as well as a RT-PCR method to determine the frequency of transmission of this pathogen to tomato seedlings. Infection frequency of PSTVd in tomato seeds from infected plants (cv. ‘Beefsteak’) ranged from 62.3-69% and frequency of PSTVd transmission to tomato seedlings was 50.9%. Germination of the infected seed was significantly lower (53%) than the parent seed (98%), and we also determined that viroid titers in the infected seeds were significantly lower (average 173 ng/μl) than in the infected seedlings (785 ng/μl). Interestingly ~60% of the infected seedlings did not display any observable symptoms of PSTVd until the second or third week; however, plants that were grown to maturity developed severe symptoms, suggesting that a grow-out assay might not be an accurate method for detection of this pathogen.