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

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 a 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 the yellow leaf susceptible sugarcane cultivar CP96-1252. 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) 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 healthy plants became infected during a 24-to 28-month period. SCYLV prevalence in these field experiments did not differ between aphicide treated and untreated plots. Incidence of M. sacchari haplotypes in the Everglades agricultural area also indicated that the predominant haplotype that 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.

Morphometric and molecular discrimination of the sugarcane aphid, Melanaphis sacchari, (Zehntner, 1897) and the sorghum aphid Melanaphis sorghi (Theobald, 1904)

“…Although our sampling plan was not designed to test host plant preference, the difference of preference between the two species appears obvious. The results of Boukari et al [ 38 ] obtained in Florida confirm this preference, showing that sugarcane harbors almost only M . sacchari (COI haplotypes H2 and H3), which is absent from aphids on Sorghum spp.…”

Present Status and Future Management Strategies for Sugarcane Yellow Leaf Virus: A Major Constraint to the Global Sugarcane Production

“…Recently, three inherently dissimilar haplotypes of M. sacchhari were reported from United States including haplotype one (H1) infecting Sorghum species and sugarcane whereas, H3 haplotype known to occur on sugarcane, sorghum and Johnsongrass (S. halepense) and H6 haplotype colonizes both sugarcane and Johnsongrass (Nibouche et al, 2018). Moreover, from Florida, lack of efficient transmission of SCYLV from sugarcane and Columbus grass to sugarcane has been shown by M. sacchari and mites (Oligonychus grypus), suggesting the SCYLV vector needs further identification (Boukari et al, 2020).…”

Natural occurrence and diagnosis of yellow leaf disease affecting sugarcane genotypes under tropical and sub-tropical conditions in India

“…As SCYLV is one of the causal pathogens of YLD, recently, Boukari et al (2020) investigated the transmission efficiency of SCYLV by aphid (Melanaphis sacchari) on YLD susceptible sugarcane cultivar CP96-1252 and the inoculated plants were found negative for the presence of SCYLV by tissue blot immunoassay (TBIA) and reverse transcription polymerase chain reaction (RT-PCR). The results revealed that the M. sacchari is one of the prominent vector of SCYLV in different parts of the world but it is not a vector of SCYLV in Florida.…”