Differential accumulation and transmission of traditional and emergent Beet curly top virus strains from of the western United States

Authors: Wintermantel, William - Bill; Hladky, Laura; Cortez, Arturo; CHEN, LI-FANG - University Of California; GILBERTSON, ROBERT - University Of California

Submitted to: American Society of Sugar Beet Technologists
Publication Type: Abstract Only
Publication Acceptance Date: 10/17/2016
Publication Date: 2/27/2017
Citation: Wintermantel, W.M., Hladky, L.L., Cortez, A.A., Chen, L., Gilbertson, R.L. 2017. Differential accumulation and transmission of traditional and emergent Beet curly top virus strains from of the western United States. American Society of Sugar Beet Technologists. February 27-March 2, 2017, Greenville, South Carolina.

Interpretive Summary: Curly top disease, caused by various strains of Beet curly top virus (BCTV), causes significant economic losses for sugarbeet throughout the western United States. Recent surveys in California and the Pacific Northwest have identified a rapid shift in the predominant strains of BCTV impacting agriculture, with new emergent strains supplanting traditional strains of the virus in both regions. As a result, some changes in severity and affected host plants have been noted, and this may reflect the prevalence and dominance of the new strains over traditionally common strains. To identify factors leading to emergence of new strains, competition studies were conducted in which sugarbeet and other host plants were inoculated as single or co-infections with new and traditional BCTV strains using Agro-inoculation of cloned virus. Some infections were established using leafhopper transmission due to difficulty in obtaining viable infection with clones of specific strains using the Agro-inoculation method. After four weeks, test plants were evaluated for virus accumulation using qPCR, and used for leafhopper transmission to new test plants, followed by determination of which strains transmitted most effectively. Results demonstrated preferential accumulation of some strains in a host plant-specific manner. This indicated some BCTV strains are better adapted to some host plants than others, and that host plants may have a profound influence on emergence and dominance of BCTV strains. Secondarily, studies also suggested that accumulation of BCTV strains that have difficulty in establishing infections from clones cannot be compared reliably using Agro-inoculation, because these strains are at a selective disadvantage in establishing infections. Results have implications for virus propagation for curly top nurseries, and begin to clarify factors that contribute to the relatively sudden emergence of new BCTV strains in the western United States.

Technical Abstract: Curly top disease, caused by various strains of Beet curly top virus (BCTV), causes significant economic losses for sugarbeet throughout the western United States. Recent surveys in California and the Pacific Northwest have identified a rapid shift in the predominant strains of BCTV impacting agriculture, with new emergent strains supplanting traditional strains of the virus in both regions. As a result, some changes in severity and affected host plants have been noted, and this may reflect the prevalence and dominance of the new strains over traditionally common strains. To identify factors leading to emergence of new strains, competition studies were conducted in which sugarbeet and other host plants were inoculated as single or co-infections with new and traditional BCTV strains using Agro-inoculation of cloned virus. Some infections were established using leafhopper transmission due to difficulty in obtaining viable infection with clones of specific strains using the Agro-inoculation method. After four weeks, test plants were evaluated for virus accumulation using qPCR, and used for leafhopper transmission to new test plants, followed by determination of which strains transmitted most effectively. Results demonstrated preferential accumulation of some strains in a host plant-specific manner. This indicated some BCTV strains are better adapted to some host plants than others, and that host plants may have a profound influence on emergence and dominance of BCTV strains. Secondarily, studies also suggested that accumulation of BCTV strains that have difficulty in establishing infections from clones cannot be compared reliably using Agro-inoculation, because these strains are at a selective disadvantage in establishing infections. Results have implications for virus propagation for curly top nurseries, and begin to clarify factors that contribute to the relatively sudden emergence of new BCTV strains in the western United States.