The disease caused by the "Mal de Rio Cuarto virus" (MRCV) is one of the most important diseases among those affecting maize (Zea mays) crops in Argentina. The MRCV belongs to the Reoviridae family, within the Fijivirus genus. It is spread in nature by Delphacodes kuscheli (Hemiptera: Delphacidae). The manner of transmission of the members of this virus genus is persistent propagative. An efficient virus transmission system was arranged in order to perform the various characterisation studies. These studies were carried out with healthy vector populations raised in the laboratory. Different acquisition, latency and inoculation periods were tested and a range of differential hosts was also evaluated, by breeding in phytotrons and controlled atmosphere chambers. A sufficient number of virus-free insects could thus be obtained to perform work. Experimental transmission of MRCV was successfully accomplished under identical conditions with acquisition, latency and inoculation periods of two, 10 and one days for fine grain cereals and two, 10 and two days for maize respectively. The following species were infected in this manner: maize (Zea mays), barley (Hordeum vulgare), oats (Avena sativa), wheat (Triticum aestivum), rye (Secale cereale), grama rhodes (Chloris gayana) and birdseed (Phalaris canariensis). Virus detection in inoculated plants was performed by means of serological tests, electrophoresis of the dsRNA in polyacrylamide gel (which showed the 10 typical bands of the fijiviruses) and electron microscopy, which showed 60 - 70 nm isometric particles.
