Infectious clones development and transmission biology of maize chlorotic mottle virus

Abstract

Maize chlorotic mottle virus (MCMV) has become one of the most widespread corn viruses in the Hawaiian Islands. In the US Mainland, MCMV has been reported to be transmitted by chrysomelid beetles. However, none of these beetle species are established in Hawaii where the corn thrips, Frankliniella williamsi has been identified to be the main vector. In this research, I showed that thrips transmitted the virus with no evidence for latent periods. Both larvae and adults transmitted MCMV for up to 6 days after acquisition, with decreasing rates of transmission as time progressed. There was also no evidence that adult thrips that acquired the virus as larvae were competent vectors. Real-time RT-PCR assays showed that viral load was depleted from the vector's body after thrips had access to healthy plant tissue. Depletion of viral load was also observed when thrips matured from larvae to adults. Thrips were able to transmit MCMV after acquisition and inoculation access periods of 3 hours. In addition, I used an artificial feeding assay to feed thrips on purified MCMV or MCMV genomic RNA. Based on results achieved, I postulated that MCMV employs a capsid strategy for vector transmission. To further study the molecular determinants in MCMV transmission by vectors, I developed infectious clones of MCMV using a long RT-PCR assay. Taken altogether this research suggests that corn thrips transmit MCMV in a semi-persistent manner and that MCMV employs a capsid strategy for vector transmission.