Heterogeneity of Maize rough dwarf fijivirus genomic segments isolated from 1997 field infection

The genomic dsRNAs extracted from individual maize plants collected in Ital y, each naturally infected by Maize rough dwarf fijivirus (MRDV), showed di stinct electrophoretic mobilities. The genomic segments differing in mobili ties were randomly distributed throughout all the 10 genomic complements, e ven when derived from plants collected in the same field. Different genomic electropherotypes were not correlated with symptom expression. Several ele ctropherotypes were occasionally harbored in the same plant with typical MR DV symptoms. MRDV dsRNAs purified from a mixture of plants collected in the field showed an electrophoretic migration pattern reflecting a mixture of individual profiles. MRDV planthopper vectors (Laodelphax striatellus Falle n) were used to isolate and keep in separate cultures different MRDV electr opherotypes. Natural and experimentally obtained phenotypic variants of pla nt-infecting reoviruses belonging to other genera within the Reovividae hav e been described: here, we report a direct comparison of MRDV electropherot ypes experimentally isolated from naturally infected plants.