High risk blueberry viruses by region in the North America; implications for certification, nurseries, and fruit production

Authors: Martin, Robert; TZANETAKIS, IOANNIS - University Of Arkansas

Submitted to: Viruses
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2018
Publication Date: 6/26/2018
Citation: Martin, R.R., Tzanetakis, I.E. 2018. High risk blueberry viruses by region in the North America; implications for certification, nurseries, and fruit production. Viruses. 10(7):342-350. https://doi.org/10.3390/v10070342.
DOI: https://doi.org/10.3390/v10070342

Interpretive Summary: The information on high risk viruses for blueberries in the U.S. and British Columbia, Canada can be used by growers to manage virus diseases in production fields, by State Departments of Agriculture to manage more efficiently certification programs and by nurseries to inform the development of their pest management plan. Certification programs are based on best management practices (BMPs) to minimize the risk of virus infection, combined with virus testing to ensure the BMPs are effective. The testing done should focus viruses most likely to spread in the area where the nursery is located. Few if any of the viruses in blueberry cause visual symptoms in all cultivars, which highlight the importance of doing some testing of nursery stocks and not relying on visual inspections. In nurseries the goal should be to control all viruses to minimize the risk of distributing symptomless viruses to production fields. This is especially important with the movement of plant materials across state and country borders, where introducing new viruses to a region could put existing production at risk. If nurseries get there material from a clean plant center where the material has been tested and found free of known viruses, then monitoring should focus on viruses spread most rapidly in the area, with some testing for other viruses at the top two tiers of propagation.

Technical Abstract: There is limited information about the distribution of blueberry viruses in the U.S. or around the world other than where the viruses were first discovered and characterized. A survey for blueberry viruses was carried out in the U.S. in 2015-2017. With the lack of a reliable woody indicator, most blueberry viruses have been characterized to the point that sensitive diagnostic assays have been developed. These assays are based on ELISA or variations of PCR, which were employed here to determine the presence of blueberry viruses in major blueberry production and nursery areas of the U.S. The viruses evaluated in this study were: blueberry fruit drop, blueberry latent (BlLV), blueberry leaf mottle (BLMoV), blueberry mosaic, blueberry red ringspot (BRRV), blueberry scorch (BlScV), blueberry shock (BlShV), blueberry shoestring (BlSSV), blueberry virus A (BVA), peach rosette mosaic (PRMV), tobacco ringspot (TRSV), and tomato ringspot virus (ToRSV). In the Pacific Northwest BlShV was the most widespread virus, with BlScV and ToRSV detected in a limited number of fields in Oregon and Washington, but widespread in British Columbia. In the upper mid-west, the nematode-borne (ToRSV, TRSV) and aphid-transmitted (BlSSV and BVA) and pollen-borne (BLMoV) transmitted viruses were most widespread. In the northeastern U.S., TRSV, ToRSV, BlScV, were detected most frequently. In the southeast U.S., BRRV and BNRBV were the most widespread. BlLV, a cryptic virus with no known symptoms or effect on plant growth or yield in either single or mixed infections was present in all regions. There are other viruses present at low levels in each of the areas, but with the lower incidence they pose a lower threat to nursery systems or fruit production. These results indicate that there are hotspots for individual virus groups that normally coincide with the presence of the vectors. The information presented highlights the high risk viruses for nursery production, where efforts are made to control all viruses, and fruit production, where efforts are made to control virus diseases.