Diagnostic of begomoviruses in complex infections -a case study

Complexes of viruses inducing a syndrome in plants strongly hinder the identification of the causal agent of a disease. The Sida micrantha mosaic disease is associated with a complex of begomoviruses. For more than twenty years, two DNAs A (DNA A2 and DNA A3) belonging to this complex could neither be detected nor isolated from Sida micrantha Schr. plants, although one of them (DNA A2) now appears to be the major component of the complex. A random unintended Bemisia tabaci-mediated transmission of begomoviruses from several Sida species - including S. micrantha - to experimental Malva parviflora plants resulted in the serendipitous finding of these new DNAs A. Simultaneously, a number of other begomoviruses infecting Sida plants from several Latin American countries were transmitted to M. parviflora plants and the convergence of them resulted in natural pseudorecombinants. Pseudorecombination, however, took place exclusively between heterologous genomic components that shared identical binding sites for the replication-associated protein AC1. This case study constitutes an exceptional opportunity for the analysis of plant-virus- vector interactions in a quasi-natural environment. In addition to that, the methodology described here may be used to isolate and characterize different begomoviruses inducing a syndrome during mix infections.