NUCLEOTIDE-SEQUENCE EVIDENCE FOR THE OCCURRENCE OF 3 DISTINCT WHITEFLY-TRANSMITTED SIDA-INFECTING BIPARTITE GEMINIVIRUSES IN CENTRAL-AMERICA

The nucleotide sequences of two Sida-infecting geminiviruses from Hond uras were determined. The symptoms of both viruses are identical in Si de rhombifolia but different in Nicotiana benthamiana. An additional s ymptom of one virus was yellow vein clearing on infected N. benthamian a leaves. Both Sida golden mosaic viruses (SiGMV-Ho and SiGMV-Ho-yv) h ave bipartite genomes (DNAs A and B). From the SiGMV-Ho-yv-infected S. rhombifolia plant two different DNA B molecules were isolated and clo ned. They differ in length by 24 nucleotides [SiGMV-Ho-yv B-1 (2593 nt ) and B-2 (2569 nt)] and at eight nucleotide positions. Both proteins encoded by DNA B (BV1 and BC1) are affected by these substitutions. Co mputer analysis shows that the bipartite genomes resemble those of oth er whitefly-transmitted geminiviruses. From homology analyses we concl ude that both viruses are closely related but distinct. Comparison wit h a Sida-infecting virus from Costa pica (SiGMV-Co) showed that the tw o viruses from Honduras are more similar to each other than either of them are to SiGMV-Co. Exchange of SiGMV-Ho and SiGMV-Ho-yv genomic com ponents resulted in viable pseudorecombinant viruses. SiGMV-Ho DNA A w as able to produce a viable pseudorecombinant with SiGMV-Co DNA B whil e the reciprocal exchange was not infectious in N. benthamiana. SiGMV- Ho-yv DNA A and SiGMV-Co DNA B produced a viable pseudorecombinant vir us whereas only pseudorecombination of SiGMV-Co DNA A with SiGMV-Ho-yv DNA B-2, and not with DNA B-1, was infectious in N. benthamiana.