Determinants of tomato golden mosaic virus symptom development located on DNA B.

Infectious clones have been constructed from two strains of the bipartite geminivirus tomato golden mosaic virus. The common strain and the yellow vein strain show marked phenotypic differences in Nicotiana benthamiana which are reproduced following infection with the cloned viral genomes. Pseudorecombinants between the two strains, produced by exchange of genome components (DNAs A and B), established that the difference in symptoms in several species of the Solanaceae is determined by DNA B. Recombinants produced in vitro between the DNA B components showed that determinants of symptom development map to the common region and gene BL1. DNA B is known to carry functions necessary for spread of viral DNA through the host plant. Our results emphasize the link between symptom type and virus spread.