Eight species of Poaceae are hosting different genetic and pathogenic strains of sugarcane mosaic virus in the Everglades Agricultural Area

Authors: HINCAPIE, MARTHA - University Of Florida; Sood, Sushma; Mollov, Dimitre; ODERO, CALVIN - University Of Florida; Grisham, Michael; ROTT, PHILIPPE - Cirad, France

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/2021
Publication Date: 2/23/2021
Citation: Hincapie, M., Sood, S.G., Mollov, D.S., Odero, C.D., Grisham, M.P., Rott, P. 2021. Eight species of Poaceae are hosting different genetic and pathogenic strains of sugarcane mosaic virus in the Everglades Agricultural Area. Phytopathology. https://doi.org/10.1094/PHYTO-11-20-0489-R.
DOI: https://doi.org/10.1094/PHYTO-11-20-0489-R

Interpretive Summary: Sugarcane mosaic virus (SCMV) infects many plants in the grass family, especially sugarcane where it causes economic losses by reducing yields. We used molecular techniques to identify eight grasses that are hosts of SCMV in the Everglades Agricultural Area (EAA) area of Florida: broadleaf signal grass Columbus grass, goosegrass, maize, sorghum, St. Augustine grass, southern crabgrass, and sugarcane. Inoculation experiments revealed different patterns of susceptibility to different virus isolates, which helps understand the complex ways that SCMV may be spread in the EAA. For example, the SCMV isolates from Columbus grass did not infect sugarcane, suggesting this common weed is not a source from which the virus spreads into production sugarcane. This helps understand SCMV epidemiology and will aid in SCMV management in Florida. This research also generated sequence data for 62 isolates of SCMV, and contributed to a better understanding of the genetic diversity of this globally-occurring virus.

Technical Abstract: Sugarcane mosaic virus (SCMV) was detected by reverse-transcription polymerase chain reaction in eight different species of the Poaceae family in the Everglades Agricultural Area (EAA) of south Florida: Broadleaf signal grass (Urochloa platyphylla), Columbus grass (Sorghum almum), goosegrass (Eleusine indica), maize (Zea mays), sorghum (Sorghum bicolor), St. Augustine grass (Stenotaphrum secundatum), southern crabgrass (Digitaria ciliaris), and sugarcane (Saccharum interspecific hybrids). Based on their coat protein (CP) sequence, 62 isolates of SCMV from Florida and 29 worldwide isolates representing the known genetic diversity of this virus were distributed into six major phylogenetic groups. Columbus grass, maize, and sorghum isolates of SCMV from Florida formed a unique group whereas sugarcane isolates from the USA (Florida and Louisiana) clustered with isolates from other countries. Based on the entire genome coding region and among Florida isolates, sugarcane isolates were closest to SCMV from sorghum species or from St. Augustine grass. Virus isolates from Columbus grass, St. Augustine grass, and sugarcane showed different virulence patterns after mechanical inoculation of all three host plants, thus proving that these isolates were different pathogenic strains of SCMV. Sugarcane was symptomless and tested negative for SCMV by tissue blot immunoassay after inoculation with the virus from Columbus grass, indicating that Columbus grass was not a reservoir for SCMV infecting sugarcane in the EAA. Close CP sequence identity between isolates of SCMV from Columbus grass, maize, and sorghum suggested that the same virus strain was naturally spreading among these three plants in south Florida.