Occurrence, sequence polymorphism and population structure of Circulifer tenellus virus 1 in a field population of the beet leafhopper

Circulifer tenellus virus 1 (CiTV1) is the prototypical example of an unusual group of dsRNA viruses associated with insects and for which ecological data are lacking. A San Joaquin Valley (SJV), California population of the beet leafhopper (BLH; Circulifer tenellus [Baker]) was sampled for CiTV1 in 2010. Among 365 BLH sampled, 119 (32.6%) were positive for CiTV1, with at least one CiTV1-positive BLH collected from each of 35 locations. Chi-square tests indicated that observed CiTV1 incidence differed from expected values based on collection season but not geography within the SJV. Sequence comparisons identified three CiTV1 strains, designated A, B, and C. Strain A predominated (82.4%), strain B was less common (16.8%), and only one (0.8%) strain C isolate was encountered. Chi-square tests demonstrated that observed frequencies of strains A and B did not differ from expected values in space or time, indicating that the SJV population of CiTV1 was unstructured.