November 17, 2003
From: British Society for Plant Pathology, New Disease Reports, Vol. 8 [edited]

C. I. Dovas, K. Eythymiou and N. I. Katis <katis@agro.auth.gr>, Aristotle University of Thessaloniki, Faculty of Agriculture, Plant Pathology Laboratory, 54 124 Thessaloniki, Greece. Accepted for publication 27/10/03

In summer 2002, maize (_Zea mays_ L.) crops in northern Greece (Macedonia), showed severe dwarfing, reduced corn cob size and in some cases leaf reddening. These symptoms were different from those caused by Maize dwarf mosaic virus, which is endemic in maize crops in Macedonia.

The dwarfing disease was only epidemic in 2002 and in some maize growing regions (Imathia and Serres), where crop losses were estimated to be over 70 percent. In contrast, in 2003 only a few cases were recorded.

Symptoms were similar to those caused by 2 closely related members of the genus Fijivirus, Maize rough dwarf virus (MRDV), and Rice black-streaked dwarf virus (RBSDV) (Azuhata et al., 1993). The putative virus could not be transmitted mechanically from maize to maize or to other indicator plants. 

An RT-PCR was developed and optimised for the detection of both MRDV and RBSDV. 2 primers ('MRDV-F1': 5'-AGCGGAGAACGTTtggatc-3' and 'MRDV-R2': 5' -ttaacaacagcagcttcacc-3') were designed from highly conserved regions within both viral genomes (segment 8 from MRDV and 9 from RBSDV).

Total RNA was extracted, denatured at 95 C in the presence of 1 micromole of primer 'MRDV-R2' and 10 percent DMSO, before being used as template for RT. RT and subsequent PCR were performed according to standard protocols (Dovas et al., 2001) with an annealing temperature of 60 C used in PCR.

RT-PCR using total RNA from 15 plants showing typical dwarfing symptoms gave the expected 568 bp product, which was subsequently cloned and sequenced. Sequence comparisons revealed 96 percent identity with genome segment 8 of an Italian isolate of MRDV (L76561) (Marzachi et al., 1996), whereas identity with genome segment 9 of two RBSDV isolates from China (AF459812, AY050486) was 85 percent (Bai et al., 2002).

The presence of MRDV was further confirmed by ELISA using polyclonal antibodies (BioRad Phyto-Diagnostics, France). More than 50 samples collected from Imathia and Serres area, showing MRDV symptoms tested positive by ELISA.

This is the first report of MRDV in Greece.

References
Azuhata F, Uyeda I, Kimura I, Shikata E, 1993. Close similarity between genome structures of rice black-streaked dwarf and maize rough dwarf viruses. Journal of General Virology 74, 1227-1232.
Bai FW, Yan J, Qu ZC, Zhang HW, Xu J, Ye MM, Shen DL, 2002. Phylogenetic analysis reveals that a dwarfing disease on different cereal crops in China is due to Rice black streaked dwarf virus (RBSDV). Virus Genes 25, 201-206.
Dovas CI, Hatziloukas E, Salomon R, Barg E, Shiboleth Y, Katis N, 2001. Comparison of methods for virus detection in Allium spp. Journal of Phytopathology 149, 731-737.
Marzachi C, Antoniazzi S, Aquilio M, Boccardo G, 1996. The double-stranded RNA genome of maize rough dwarf Fijivirus contains both mono and dicistronic segments. European Journal of Plant Pathology 102, 601-605.