Hernandez, C., & Brown, J. K. (2010). First report of a new curtovirus species, Spinach severe curly top virus, in commercial Spinach plants (Spinacia oleracea) from South-Central Arizona. Plant Disease, 94(7), 917-.
Legg, J. P., Sseruwagi, P., Boniface, S., Okao-Okuja, G., Shirima, R., Bigirimana, S., Gashaka, G., Herrmann, H., Jeremiah, S., Obiero, H., Ndyetabula, I., Tata-Hangy, W., Masembe, C., & Brown, J. K. (2013). Spatio-temporal patterns of genetic change amongst populations of cassava Bemisia tabaci whiteflies driving virus pandemics in East and Central Africa. Virus Research.
Abstract:
The greatest current threat to cassava in sub-Saharan Africa, is the continued expansion of plant virus pandemics being driven by super-abundant populations of the whitefly vector, Bemisia tabaci. To track the association of putatively genetically distinct populations of B. tabaci with pandemics of cassava mosaic disease (CMD) and cassava brown streak disease (CBSD), a comprehensive region-wide analysis examined the phylogenetic relationships and population genetics of 642 B. tabaci adults sampled from cassava in six countries of East and Central Africa, between 1997 and 2010, using a mitochondrial DNA cytochrome oxidase I marker (780 bases). Eight phylogenetically distinct groups were identified, including one, designated herein as 'East Africa 1' (EA1), not previously described. The three most frequently occurring groups comprised >95% of all samples. Among these, the Sub-Saharan Africa 2 (SSA2) group diverged by c. 8% from two SSA1 sub-groups (SSA1-SG1 and SSA1-SG2), which themselves were 1.9% divergent. During the 14-year study period, the group associated with the CMD pandemic expansion shifted from SSA2 to SSA1-SG1. Population genetics analyses of SSA1, using Tajima's D, Fu's F s and Rojas' R 2 statistics confirmed a temporal transition in SSA1 populations from neutrally evolving at the outset, to rapidly expanding from 2000 to 2003, then back to populations more at equilibrium after 2004. Based on available evidence, hybrid introgression appears to be the most parsimonious explanation for the switch from SSA2 to SSA1-SG1 in whitefly populations driving cassava virus pandemics in East and Central Africa. © 2013 Elsevier B.V. All rights reserved.
Brown, J. K., & Idris, A. M. (2014). Viral metagenomics: validation of genome enrichment coupled with Next Generation Sequencing reveals reproducibility between laboratory and field samples, and reveals polymorphisms in begomovirus populations from natural plant infections. Viruses, 6, 1219-1236.
Idris, A., Al-Saleh, M., Piatek, M.J., Al-Shahwan, I., Ali, S., and Brown, J.K. 2014. Viral metagenomics: validation of genome enrichment coupled with Next Generation Sequencing reveals reproducibility between laboratory and field samples, and reveals polymorphisms in begomovirus populations from natural plant infections. Viruses 6:1219-1236; doi:10.3390/v6031219
Brown, J. K., Idris, A. M., Ostrow, K. M., Goldberg, N., French, R., & Stenger, D. C. (2005). Genetic and phenotypic variation of the Pepper golden mosaic virus complex. Phytopathology, 95(10), 1217-1224.
PMID: 18943475;Abstract:
Three isolates of the bipartite begomovirus Pepper golden mosaic virus (PepGMV) were characterized for genomic and biological properties. The complete nucleotide 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). Nucleotide 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 because 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. Progeny virus derived from clones of PepGMV-Ser and -Mo were transmitted from pepper to pepper by the B biotype of Bemisia tabaci; 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.
Rehman, M., Melgar, J. C., C, J. R., Idris, A. M., & Brown, J. K. (2010). First report of "candidatus liberibacter psyllaurous" or "ca. liberibacter solanacearum" associated with severe foliar chlorosis, curling, and necrosis and tuber discoloration of potato plants in Honduras. Plant Disease, 94(3), 376-.
