Lack of transmission of Sugarcane yellow leaf virus in Florida from Columbus grass and sugarcane to sugarcane with aphids or mites

Authors: BOUKARI, WARDA - University Of Florida; WEI, CHUNYAN - University Of Florida; TANG, LIHUA - University Of Florida; HINCAPIE, MARTHA - University Of Florida; NARANJO, MORAMAY - Florida Crystals Corporation; NUESSLY, GREGG - University Of Florida; BEUZELIN, JULIEN - University Of Florida; Sood, Sushma; ROTT, PHILLIPPE - University Of Florida

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/26/2020
Publication Date: 3/6/2020
Citation: Boukari, W., Wei, C., Tang, L., Hincapie, M., Naranjo, M., Nuessly, G., Beuzelin, J., Sood, S.G., Rott, P. 2020. Lack of transmission of sugarcane yellow leaf virus in Florida from Columbus grass and sugarcane to sugarcane with aphids or mites. PLoS One. 15(3), 1-10. https://doi.org/10.1371/journal.pone.0230066.
DOI: https://doi.org/10.1371/journal.pone.0230066

Interpretive Summary: Sugarcane yellow leaf virus (SCYLV) naturally infects at least three plant species in Florida: sugarcane, the weed Columbus grass, and cultivated sorghum. All three hosts are also colonized by the sugarcane aphid, a main vector of SCYLV worldwide. To better understand the high incidence of SCYLV observed in sugarcane commercial fields and in germplasm collections, we investigated the transmission efficiency of SCYLV from sugarcane and Columbus grass to sugarcane using the sugarcane aphid and the spider mite that also tested positive for SCYLV in Florida. Healthy and SCYLV-infected leaf pieces of sugarcane and Columbus grass carrying viruliferous aphids or spider mites were transferred to virus-free plants of sugarcane cultivar CP96-1252 susceptible to yellow leaf. Three- and 6-months post inoculation, the 108 aphid-inoculated plants of Columbus grass and the 90 mite-inoculated plants of sugarcane tested negative for SCYLV by tissue blot immunoassay and/or reverse transcription polymerase chain reaction. Similar results were obtained for 162 aphid-inoculated sugarcane plants, except for two plants that tested positive for SCYLV. In two field experiments planted with SCYLV-free and virus-infected sugarcane, only 18-28% of plants became infected during a 24 to 28-month period. No significant difference in SCYLV prevalence was found between plots treated with an aphicide and untreated plots. This also indicated that the predominant haplotype of sugarcane aphid which is currently colonizing sugarcane was not a vector of SCYLV in Florida. Lack of virus transmission by the spider mite suggested that this arthropod only acquired the virus when feeding on infected plants but was unable to transmit SCYLV.

Technical Abstract: Sugarcane yellow leaf virus (SCYLV), the causal agent of yellow leaf disease, naturally infects at least three plant species in Florida: sugarcane (Saccharum spp.), the weed Columbus grass (Sorghum almum) and cultivated sorghum (S. bicolor). All three hosts are also colonized by the sugarcane aphid (Melanaphis sacchari), the main vector of SCYLV worldwide. To understand the high incidence of SCYLV observed in sugarcane commercial fields and in germplasm collections, we investigated the transmission efficiency of SCYLV from sugarcane and Columbus grass to sugarcane using the sugarcane aphid and the spider mite Oligonychus grypus that also tested positive for SCYLV in Florida. Healthy and SCYLV-infected leaf pieces of sugarcane and Columbus grass carrying viruliferous aphids or spider mites were transferred to virus-free plants of sugarcane cultivar CP96-1252 susceptible to yellow leaf. Three- and 6-months post inoculation, the 108 aphid-inoculated plants of Columbus grass and the 90 mite-inoculated plants of sugarcane tested negative for SCYLV by tissue blot immunoassay (TBIA) and/or reverse transcription polymerase chain reaction (RT-PCR). Similar results were obtained for 162 aphid-inoculated plants of sugarcane, except for two plants that tested positive for SCYLV by TBIA and RT-PCR. In two field experiments planted with SCYLV-free and virus-infected sugarcane (cultivar CP96-1252), only 18-28% of plants became infected during a 24 to 28-month period. No significant difference in SCYLV prevalence was found between plots treated with an aphicide and untreated plots. This also indicated that the predominant haplotype of M. sacchari which is currently colonizing sugarcane was not a vector of SCYLV in Florida. Lack of virus transmission by the spider mite suggested that this arthropod only acquired the virus when feeding on infected plants but was unable to transmit SCYLV. The current vector of SCYLV in Florida remains to be identified.