Submitted to: Phytopathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/26/2005
Publication Date: 10/1/2005
Citation: Brown, J.K., Idris, A.M., Ostrow, K., Goldberg, N., French, R.C., Stenger, D.C. 2005. Genetic and phenotypic variation of the pepper golden mosaic virus complex. Phytopathology 95:1217-1224. Interpretive Summary: Three isolates of the whitefly-transmitted Pepper golden mosaic virus (PepGMV) were characterized for variability in genetic composition, ability to cause disease on a variety of crop and weed species, and transmission by the sweet potato whitefly. For each isolate, the two DNA components of the viral genome were cloned and the complete nucleotide sequence of each determined. Comparisons of DNA sequences indicated that the three isolates may be considered as strains of a single species. Inoculation of cloned viral DNA onto plants resulted in viral infection and demonstrated that the PepGMV isolates differed in the type of disease symptoms. Whitefly transmission assays indicated that only two of the three isolates could be transferred from plant to plant by whiteflies. When different pairs of the two DNA components were mixed, the resulting infections on plants indicated that the severity and type of symptoms produced were determined by the viral DNA B component. Collectively, these results indicate that isolates of PepGMV have the capacity to exchange genetic material and that reassortment may lead to new variants that differ in the severity of disease produced on crop species.
Technical Abstract: Three isolates of the bipartite begomovirus Pepper golden mosaic virus (PepGMV) were characterized for genomic and biological properties. The complete nucleotide (nt) sequences of the DNA-A and DNA-B components were determined from infectious clones of PepGMV-Serrano (PepGMV-Ser), PepGMV-Mosaic (PepGMV-Mo), and PepGMV-Distortion (PepGMV-D). Nt sequence identity among PepGMV components ranged from 91 to 96% for DNA-A and from 84 to 99% for DNA-B, with each PepGMV component most closely related to the corresponding component of Cabbage leaf curl virus (CaLCV). However, phylogenetic relationships among begomovirus components were incongruent as DNA-A of PepGMV and CaLCV share an inferred evolutionary history distinct from that of DNA-B. The cloned components of PepGMV-Ser, -Mo, and -D were infectious by biolistic inoculation to pepper but differed in symptom expression: PepGMV-Ser exhibited a bright golden mosaic, PepGMV-Mo produced a yellow-green mosaic, and PepGMV-D caused only a mild mosaic and foliar distortion followed by a ‘recovery’ phenotype in which leaves developing after initial symptom expression appeared normal. Differences in symptoms also were observed on tomato, tobacco, and Datura stramonium L. Progeny virus derived from clones of PepGMV-Ser and -Mo were transmitted from pepper to pepper by the B biotype of Bemisia tabaci (Genn.); progeny virus derived from PepGMV-D clones was not transmissible by the B biotype. Reassortant genomes derived from heterologous DNA components of the three isolates were infectious in all possible pairwise combinations with symptom phenotype in pepper determined by the DNA-B component. Collectively, these results indicate that the three virus isolates examined may be considered distinct strains of PepGMV that have the capacity to exchange genetic material.