First Report of Maize chlorotic mottle virus Infecting Sugarcane (Saccharum officinarum)

The experimental host range of Maize chlorotic mottle virus (MCMV) is restricted to the Gramineae (Poaceae) family with maize as a natural host. However, MCMV has never been found to infect sugarcane (Saccharum officinarum L.) plants in fields. MCMV can cause corn lethal necrosis disease (CLND) resulting from synergistic interaction between this virus and Maize dwarf mosaic virus (MDMV), Wheat streak mosaic virus (WSMV), or Sugarcane mosaic virus (SCMV) (1). MCMV was first found on maize plants in Yunnan Province in China in 2011 (2), and co-infection of MCMV and SCMV was reported on maize in Yunnan Province in China in 2013 (1). In January 2013, while surveying MCMV on maize in Yunnan Province, we found sugarcane planted near an MCMV-infected maize field with chlorotic and mosaic viral symptoms. Five symptomatic sugarcane plants were collected and screened for MCMV using a monoclonal antibody-based dot-ELISA (1). MCMV was detected in all five sugarcane samples using this assay. To further confirm the ELISA results, total RNA was isolated from sugarcane leaves using TRIzol reagent (Invitrogen, Carlsbad, CA) and assayed for MCMV by reverse transcription (RT)-PCR with primers M69F (ACAGGACACCGTTGCCGTTTAT) and M70R (CATGGGTGGGTCAAGGCTTACT) designed to amplify nt 3301 to 4282 of MCMV maize isolate YN2 (GenBank Accession No. JQ982468). The expected 982-bp amplicon was obtained from all five sugarcane samples confirming that the five sugarcane samples were infected with MCMV. Using purified total RNA as a template, RT-PCR was performed using SuperScript III Reverse Transcriptase (Invitrogen, Carlsbad, CA) and Pfusion High-Fidelity DNA polymerase (New England Biolabs, Ipswich, MA) with primers M10 (AGGTAATCTGCGGCAACAGACC, 1 to 22 nt) and M36 (GGGCCGGAAGAGAGGGGCATTAC, 4436 to 4414 nt). The sequence of the resulting cDNA amplicon (KF010583) indicated that the MCMV sugarcane isolate shares 99% sequence identity with the MCMV maize isolate YN2 from Yunnan Province in China. Attempts to mechanically transmit MCMV from sugarcane to maize were unsuccessful. However, quantitative real time RT-PCR result revealed that the virus titer in sugarcane plants was about 6 to 10 times lower than that in maize plants (data not shown). SCMV was also detected in the five MCMV-infected sugarcane samples by RT-PCR with primers W48F (GTGTGGAATGGTTCACTCAAAGCTG) and W49R (GGTGTTGCAATTGGTGTGTACACG), designed to amplify a 395-bp fragment of the SCMV Beijing isolate (AY042184). The sequence of the amplified products shared 98% identity with SCMV isolate JP2 (JF488065). Thus, we think chlorotic and mosaic symptoms on the sugarcane plant samples were caused by co-infection of MCMV and SCMV and the sugarcane plants harbor both viruses implicated in causing maize lethal necrosis. This study indicates that MCMV naturally infects sugarcane plants. To our knowledge, this is the first report of MCMV infecting sugarcane plants. References: (1) J.-X. Wu et al. J. Zhejiang Univ-Sci B (Biomed & Biotechnol). 14:555, 2013. (2) L. Xie et al. J. Phytopathol. 159:191, 2011.