Maize rough dwarf virus (Reoviridae) in its plathopper vector Laodelphax striatellus in relation to vector infectivity.

The infectivity of females of the planthopper vector Laodelphax striatellus given access to maize rough dwarf virus (MRDV) infected plants was assessed for up to 55 days from the end of the access period. A 3-day inoculation access period was used, and this avoided intermittent transmission. Maximum infectivity was reached c. 30 days after acquisition access and the proportion of transmitter insects then remained constant. There was no difference in the efficiency of female L. striatellus in acquiring MRDV as third instar nymphs or as adults when compared in transmission tests 24, 30, 35 and 40 days after access to the virus. ELISA tests for MRDV subviral particles (SVPs) discriminated between individual viruliferous and non-viruliferous insects from the 30th day after access. Of the viruliferous (ELISA positive) insects about 30% did not transmit MRDV and the proportion remained similar from 30 to 55 days after access. None of the non-transmitter insects tested in serial transfer transmission tests was positive in ELISA. The concentration of SVPs detected by ELISA in the transmitter hoppers continued to increase exponentially, even after maximum infectivity was reached.