Molecular diversity of ecologically distinct Mal de Río Cuarto virus isolates based on restriction fragment length...

Viruses of the species Mal de Río Cuarto virus (genus Fijivirus, family Reoviridae) cause significant economic losses in maize in Argentina. Genetic changes in the virus genome leading to better adaptation to diverse ecological conditions were postulated that would account for the increasing MRCV variability. The genomic differences between MRCV isolates from four ecologically different areas (Río Cuarto, RC; Pergamino, P; Jesús María, JM; and Tafí del Valle, TV) were studied. RT-PCR-amplified fragments comprising four genomic segments (Seg1, Seg7, Seg9 and Seg10) of MRCV isolates were compared by RFLPs and nucleotide sequences. The segments were chosen based on the proteins they encode: RNA-dependent-RNA polymerase, proteins putatively associated with tubular structures and viroplasm and the major outer capsid protein, respectively. Genetic comparison suggested that JM and TV isolates were genetically similar, but RC and P were different. Therefore, they were clustered in three genetic groups (JM = TV, RC and P). Together, nucleotide and amino acid sequence identities of the genomic segments were often above 96%. Seg1 was more variable (viral polymerase), whereas Seg7 (putative tubular structure) was the most conserved. Phylogeny analysis showed that MRCV isolates could be clustered in 'mountain area' and 'high production area' groups according to their geographical occurrence.