Location: National Germplasm Resources LaboratoryTitle: First report of Sugarcane yellow leaf virus infecting Columbus Grass (Sorghum almum) in Florida Author
|Espinoza Delgado, Henry Victor|
|Fernandez, Jose Venancio|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/28/2015
Publication Date: 12/8/2015
Citation: Espinoza Delgado, H., Kaye, C., Hincapie, M., Boukari, W., Wei, C., Fernandez, J., Mollov, D.S., Comstock, J., Rott, P. 2015. First report of Sugarcane yellow leaf virus infecting Columbus Grass (Sorghum almum) in Florida. Plant Disease. 100:1027. Interpretive Summary: Virus infections have adverse effects on yield and quality in many crops. They tend to accumulate in vegetatively propagated crops, especially if the viruses are also transmitted by vectors during the growing season. Sugarcane is affected by several viruses, including Sugarcane yellow leaf virus (SCYLV) which affects sugarcane yield and quality. Sorghum almum or Columbus grass is a perennial weed that is widely prevalent in sugarcane fields in Florida. In this research we describe Columbus grass as a new host for SCYLV. About 35% of 500 Columbus grass samples collected around Florida sugarcane growing areas were infected by SCYLV. To our knowledge this is the first report of S. almum as a host of SCYLV. This research provides new insights into the virus epidemiology and is useful for developing sugarcane disease management strategies.
Technical Abstract: Sugarcane yellow leaf virus (SCYLV) [genus Polerovirus, family Luteoviridae] is the causal agent of sugarcane yellow leaf disease. SCYLV is widespread in Florida where sugarcane was the only known natural host of this virus. During spring 2015, we collected (leaves or stalks) and tested several grasses growing near sugarcane fields for SCYLV using tissue blot immunoassay (TBIA; Schenck et al. 1997) with two different sources of antibodies. The first antibody was provided by B.E.L. Lockhart (University of Minnesota) and was produced with purified particles of SCYLV (Scagliusi and Lockhart, 2000). The second antibody was made by Pierce Scientific (http://www.pierce-antibodies.com/) using a synthetic peptide immunogen (RGPGGRSNRDVLTFTVDDLK) based on the SCYLV coat protein (S. Rutherford, unpublished data). A total of 170 samples of corn (Zea mays), 23 of elephant grass (Pennisetum purpureum), 4 of goosegrass (Eleusine indica), 13 of para grass (Urochloa mutica), and 4 of sorghum (Sorghum bicolor) all tested negative for SCYLV. However, 170 of 489 samples (35%) of Columbus grass (Sorghum almum) tested positive for SCYLV with either one or both antibodies. No symptoms of yellow leaf, such as yellowing of the lower side of the leaf midrib, were observed on the sampled plants. Luteoviridae-like isometric particles about 30 nm in diameter were observed by transmission electron microscopy in two partially purified leaf preparations from TBIA positive plants. Viral RNA for cDNA synthesis and amplification was prepared from five positive samples of Columbus grass using a modification of the simple-direct-tube method (Suehiro et al. 2005). These samples were tested by Reverse Transcription-Polymerase Chain Reaction (RT-PCR) using primers YLS111 and YLS462 targeting the coat protein of SCYLV (Abu Ahmad et al. 2006). RT-PCR was performed on an Applied Biosystems 7300 Real-Time PCR System, and the anticipated amplification product of about 350 bp was observed in an agarose gel. Confirmatory analysis was conducted on two additional TBIA positive samples of Columbus grass. Total RNA was extracted using the RNeasy Plant mini Kit (Qiagen, Hilden, Germany). A 886 bp fragment containing almost the entire coat protein of SCYLV was amplified from both samples by RT-PCR using primers 3425F and 4483R, followed by semi-nested PCR using primers OFM336f and 4483R (Amata et al. 2015). The semi-nested primer derived 572 bp coat protein sequences were 99-100% nucleotide identical to several isolates of SCYLV in GenBank (BLASTn). These different methods allowed us to confirm SCYLV infection of Columbus grass and this represents the first report of this plant as a host for the virus. This grass of the family Poaceae, also called five-year sorghum, is widely distributed in sugarcane growing areas in Florida. It may constitute an alternative host and previously unknown inoculum source of SCYLV. This research may explain why control of SCYLV using healthy virus-free seed-cane is only partially successful in Florida. Transmission of the virus from Columbus grass to sugarcane needs to be verified to investigate the importance of this potential secondary host of SCYLV in the epidemiology and control of sugarcane yellow leaf.