Biological factors affecting leafhopper transmission of purified maize chlorotic dwarf machlovirus

A helper component from maize chlorotic dwarf machlovirus (MCDV)‐infected plants was necessary for insect transmission of purified MCDV. Purified MCDV, WS strain, when acquired by membrane feeding, was transmitted by Graminella nigrifrons (Forbes) (Homoptera:Cicadellidae) which fed first on MCDV (M1 strain)‐infected maize. Conversely, feeding on MCDV‐WS‐infected maize allowed transmission of purified MCDV‐M1, indicating that the helper component was not strain specific. Viruliferous G. nigrifrons lost the ability to transmit MCDV‐M1 after feeding for 24 h on healthy maize, but retained the ability to acquire and transmit purified MCDV‐WS for up to 36 h. When G. nigrifrons fed initially on MCDV‐infected plants and then on a second strain of purified MCDV, the second strain of MCDV could be transmitted alone, suggesting that the helper component from MCDV‐infected plants was something other than the virion itself. Lengthening acquisition feeding of G. nigrifrons on MCDV‐M1‐infected maize or purified MCDV‐WS did not significantly change the transmission frequency of MCDV‐WS. Amblysellus grex (Oman), an experimental vector of MCDV, also transmitted purified MCDV‐WS after an initial acquisition feeding on MCDV‐M1‐infected maize. This suggests that the helper component is not vector species specific.