Virus-specific adaptations for the production of a pseudorecombinant virus formed by two distinct bipartite geminiviruses from Central America.

Most whitefly-transmitted geminiviruses possess bipartite genomes comprising DNAs A and B. The production of viable pseudorecombinants by reassortment of infectious cloned components is generally limited to isolates/strains of a particular virus. Following exchange of cloned genomic components of Sida golden mosaic virus from Costa Rica (SiGMV/Co) and Sida golden mosaic virus from Honduras (SiGMV/Ho(yv)), the pseudorecombinant viruses were infectious in various plant species. Three DNA B components (B(1), B(2), B(3)), different in a few nucleotides, were isolated from Sida rhombifolia naturally infected with SiGMV/Ho(yv). Only SiGMV/Ho(yv) DNA B(2) was able to form a viable pseudorecombinant with SiGMV/Co DNA A. In protoplasts, as well as in inoculated leaves, SiGMV/Co DNA A trans-replicated the heterogenomic SiGMV/Ho(yv) DNA B(1) component, indicating that impaired movement is involved in the deficiency of SiGMV/Ho(yv) DNA B(1) to form a pseudorecombinant virus with SiGMV/Co DNA A. Even after extensive mutation analysis of SiGMV/Ho(yv) DNA B(1) and B(2), we were unable to pinpoint differences in SiGMV/Ho(yv) DNA B(2) that allowed the formation of a pseudorecombinant virus with SiGMV/Co DNA A. We observed a gradual increase of infectivity from noninfectious SiGMV/Co DNA A/SiGMV/Ho(yv) DNA B(1) and B(3) pseudorecombinant virus to pseudorecombinant viruses showing normal systemic spread of both genomic components associated with symptomatic plants. Copyright 2000 Academic Press.