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Distribution and Rate of Movement of the Curtovirus Beet mild curly top virus (Family Geminiviridae) in the Beet Leafhopper

A polymerase chain reaction (PCR)-based method for the detection of the curtovirus Beet mild curly top virus (BMCTV, previously named the Worland strain of Beet curly top virus) was developed and used to investigate the BMCTV-beet leafhopper interaction. Using PCR and a BMCTV-specific primer pair, an ≈1.1-kb BMCTV DNA fragment was amplified from adult leafhoppers and from the organs involved in circulative transmission: the digestive tract, hemolymph, and salivary glands. The temporal distribution of BMCTV in the leafhopper was determined using insects given acquisition access periods (AAPs) ranging from 1 to 48 h on BMCTV-infected shepherd's purse plants. BMCTV was detected in the digestive tract after all AAPs, in the hemolymph after AAPs of 3 h or greater, and in the salivary glands after AAPs of 4 h or greater. The amount of virus detected in the hemolymph and salivary glands increased with AAP length. The virus persisted for up to 30 days in leafhoppers (given a 3-day AAP on BMCTV-infected plants) maintained on corn plants, a nonhost for BMCTV, but transovarial transmission was not detected. These results are consistent with a persistent but nonpropagative mode of circulative transmission.