Vector Competency of Aphis gossypii and Bemisia tabaci to Transmit Cotton Leafroll Dwarf Virus

A new variant of cotton leafroll dwarf virus (CLRDV) (genus: Polerovirus, family: Solemoviridae) was discovered in cotton (Gossypium hirsutum L.) fields that were reported to be infested with aphids and whiteflies in southern Alabama in 2017. Prior to the confirmation of CLRDV, speculation focused on whiteflies as a potential vector of the then-unknown virus. Although the only vector reported to transmit CLRDV to cotton is the cotton aphid, Aphis gossypii (Glover), two recombinant poleroviruses have been reported recently to be transmitted by the whitefly, Bemisia tabaci (Genn.). Due to the emergence of a new CLRDV variant in the U.S., and the recent studies on recombinant poleroviruses, conflicting messages that whiteflies and/or aphids could be transmitting CLRDV have been relayed to growers and stakeholders in the Cotton Belt. The objective of this study was to determine if A. gossypii or B. tabaci (B Mitotype) transmit CLRDV to cotton. The results demonstrated that the CLRDV-AL variant was transmissible by alate and apterous morphs of A. gossypii, but not by B. tabaci. These findings emphasize the importance of screening insect vectors for the transmission of novel plant virus variants to correctly identify the vector(s) and provide growers and stakeholders with appropriate information to make informed management decisions.