Submitted to: American Society of Sugar Cane Technologists
Publication Type: Abstract Only
Publication Acceptance Date: 5/7/2008
Publication Date: 6/1/2008
Citation: Grisham, M.P., Comstock, J.C., Li, R. 2008. Virus Strains Causing Mosaic in Louisiana and Florida Sugarcane. Journal of the American Society of Sugar Cane Technologists. 28:42-57.
Technical Abstract: Mosaic caused by Sugarcane mosaic virus (SCMV) and Sorghum mosaic virus (SrMV), respectively, affects sugarcane in Louisiana and Florida. Between 2004 and 2007, surveys were conducted in both states to determine which virus and virus strains were causing mosaic of sugarcane. In Louisiana, leaf samples were collected from 317 sugarcane plants expressing mosaic symptoms; and in Florida, 108 leaf samples were collected from plants with and without mosaic symptoms. Reverse transcriptase-polymerase chain reaction (RT-PCR) was used to identify SCMV and SrMV isolates associated with the diseased plants. No SCMV isolate was found affecting sugarcane in Louisiana, and no SrMV isolate was identified among the Florida samples. Once the virus was identified, RT-PCR-based restriction fragment length polymorphism (RFLP) analysis was used to identify the strain of each isolate. Among the Louisiana isolates, SrMV strains I, H, and M were associated with 66%, 14%, and 6% of the samples, respectively. In 7% of the samples, the virus isolate was identified as SrMV from RT-PCR results, but the RFLP analysis indicated that the strain was different from strains H, I, or M, the strains previously described for SrMV. Further characterization of these isolates is needed to determine if they represent new strains of SrMV. No RT-PCR product was produced by either the SCMV- or the SrMV-specific RT-PCR primer set for 10% of the plants showing mosaic symptoms suggesting that another virus may cause sugarcane mosaic in Louisiana. Only Sugarcane mosaic virus strain E was associated with the Florida samples and only from plants expressing mosaic symptoms. Twenty six of the Louisiana samples, including 20 that tested negative to the presence of SCMV or SrMV, and all the Florida samples were analyzed with RT-PCR for the presence of Sugarcane streak mosaic (SCSMV), a virus that has been reported to cause mosaic symptoms in sugarcane grown in several Asian countries. No sample tested positive for SCSMV. Although SCMV and SrMV have been reported to cause mosaic in Louisiana, SCMV has not detected in the state during this and earlier surveys for over 30 years. Some Louisiana commercial varieties are known to be susceptible to SCMV through artificial inoculation or from having been planted in an area where SCMV is found naturally; however, further investigation is needed to determine the susceptibility to SCMV of current Louisiana commercial varieties and germplasm sources being used as new parental material in the breeding program. In Florida, the only virus associated with mosaic in this survey was SCMV strain E. Plants of two Florida commercial varieties (CP 72-2086 and CP 89-2143) with mosaic symptoms were sampled in both states. In Florida, they were infected with SCMV; and in Louisiana, they were infected with SrMV indicating SrMV is a potential threat to commercial Florida varieties. As sugarcane breeders and pathologists continue to identify new sources of resistance to mosaic, an awareness of the genetic diversity of the virus pathogens that cause mosaic is needed when screening new germplasm.