Maize (Zea mays) has become an important crop in Poland with a constant increase in crop acreage since the 1990s. In 2007, maize plants with characteristic leaf mosaic were observed in two locations in the Wielkopolska Region near Poznań and Krotoszyn. Ninety-two samples from plants showing leaf mosaic, some leaf discoloration, stunting, or no symptoms were collected and tested for Maize dwarf mosaic virus (MDMV) and Sugarcane mosaic virus (SCMV) by double-antibody sandwich (DAS)-ELISA (Bioreba, Basel, Switzerland). SCMV was detected only in three samples with distinct leave mosaic symptoms. Electron microscopy of leaf extracts revealed numerous potyvirus-like particles. Immuno-specific electron microscopy (ISEM) with the SCMV antiserum gave positive results for all three samples. Each virus isolate was propagated by mechanical inoculation on five varieties of dent maize and three varieties of sweet maize, cockspur grass (Echinochloa crus-galli (L.) Beauv.), crab grass (Digitaria sanguinalis (L.) Scop.), and green bristle-grass (Setaria viridis (L.) P.B.). Leaf mosaic appeared 4 to 5 days postinoculation. ELISA detected all three isolates in the symptomless hosts of oat (Avena sativa L.), wheat (Triticum aestivum L.), and triticale (Triticale). The three isolates induced local leaf necrosis on sorghum (Sorghum vulgare L.), in which the virus occurred in low concentrations as determined by ELISA so infections of sorghum plants were confirmed by reverse transcription (RT)-PCR) with primers PS/PSC (1). Barley (Hordeum vulgare L.), true millet (Panicum miliaceum L.), and wind grass (Agrostis spica-venti (L.) P.B.) were not susceptible (2). Using the total RNA extracted with the RNeasy Mini Kit (Qiagen, Hilden, Germany) from leaves of inoculated maize plants, a one step RT-PCR (Qiagen) amplified a ~800-bp cDNA fragment of the coat protein gene with SCMV-specific primers PS/PSC (1). Six cDNA clones were sequenced for each isolate. Nucleotide sequences of the 823-bp cDNA clones of isolates SCMV-P1 and P2 (GenBank Accession Nos. EU761241 and EU761242, respectively) were 99% identical and each was 92% identical to the sequence of SCMV-P3 (FJ376609). The clones of SCMV-P1 and SCMV-P2 shared 99, 98, 90, and 87% nucleotide sequence identity with two German SCMV isolates (X981697 and X98168), a Spanish isolate (AM110759), the UT6 isolate from Thailand (AY630923), and the Nancheng isolate (EU346720) from China, respectively. The SCMV-P3 sequence was 98, 94, 92, 89, and 92% identical to the Mx isolate from Mexico (AY195610), a Bulgarian SCMV isolate (AJ006201), the German Seehausen (X98166) and Borsdorf (X98167) isolates, the SC-UD1 (DQ647661), the KL -- Co86032 (DQ866744) isolates from Thailand and India, and the Chinese Nanchang (EU346720) and Pengze2 (EU346718) isolates, respectively. In 2008, SCMV was again detected by ELISA in mixed infections with MDMV in samples from the Wielkopolska Region, but only sporadically, and the virus is considered not to be important economically in maize production in Poland.
References: (1) J. X. Jiang and X. P. Zhou. Arch. Virol. 147:2437, 2002. (2) D. M. Persley. Page: 1204 in: Viruses of Plants. Descriptions and Lists from the VIDE Database. CAB International, Wallingford, UK, 1996.
