Two Distinct Genotypes of Spissistilus festinus (Say, 1830) Reproduce and Differentially Transmit Grapevine Red Blotch Virus

SIMPLE SUMMARY: Two distinct genetic groupings of the treehopper, Spissistilus festinus i.e., California (CA) and Southeastern (SE), have been described but it is unknown whether they are reproducibly compatible. In addition, the CA genotype transmits grapevine red blotch virus (GRBV), but no information is available on the transmission capacity of the SE genotype. In this study, F1 offspring of mixed mating CA/SE S. festinus pairs exhibited varied physical characteristics compared to the offspring of the parental genotypes but acquired GRBV at similar rates. Likewise, the CA and SE parental genotypes acquired GRBV at similar rates, though the viral load in the salivary glands was significantly higher for SE than CA individuals and the transmission rate was significantly higher for the SE than the CA genotype. This is the first report of distinct GRBV transmission abilities of the two sexually compatible S. festinus populations, underscoring the need to study GRBV spread in the Southeastern United States. ABSTRACT: Two phenotypically similar but genetically distinct genotypes of Spissistilus festinus (Say, 1830) (Hemiptera: Membracidae), a pest of legume crops in Southern United States and a vector of grapevine red blotch virus (GRBV) in California vineyards, exist. No information is available on whether the two S. festinus genotypes, i.e., California (CA) and Southeastern (SE), are sexually compatible or whether the SE genotype can transmit GRBV. In this study, we established mixed mating S. festinus pairs for which the F1 offspring varied phenotypically compared with the offspring of same genotype pairs but acquired GRBV isolate NY175 at similar rates (p = 0.96) and with a similar viral genome copy number (p = 0.34). Likewise, rates of GRBV acquisition were alike for the two parental CA (58%, 61/105) and SE (61%, 65/106) genotypes (p = 0.74), though the GRBV copy number in the salivary glands was overall significantly higher for SE than CA individuals (p = 0.02). Furthermore, the GRBV transmission rate was significantly higher for the SE genotype (89%, 16/18) than the CA genotype (50%, 8/16) (p = 0.04). These results revealed the existence of two sexually compatible S. festinus genotypes with distinct GRBV transmission abilities, suggesting the need to study GRBV ecology in Southeastern United States and areas where the two genotypes might co-exist.