J. K. Brown is an Associate Professor in the Department of Plant Sciences and the Department of Entomology at The University of Arizona, Tucson, AZ.

Research interests include the molecular epidemiology of whitefly-transmitted geminiviruses (Begomoviruses, Family: Geminiviridae), the basis for virus-vector specificity and the ‘transmission pathway’, and the biotic and genetic variation between populations of the whitefly vector, B. tabaci, that influence the molecular epidemiology and evolution of begomoviruses.

Begomoviruses cause yield-limiting diseases of dicotyledonous plants widely used as food, fiber, and ornamentals. The begomoviruses are distributed primarily in the dry tropics and fringe-subtropical latitudes throughout the world, and are widely recognized as damaging emergent viral pathogens. These viruses are transmitted in a persistent manner by a single species of whitefly, Bemisia tabaci (Hemiptera (Homoptera): Aleyrodidae). Distinct variants of the whitefly vector are known, but precisely how this variability effects disease epidemiology and the evolution of begomoviruses is poorly studied.

A major focus is the molecular epidemiology of begomoviruses, phylotaxonomic placement through sequence and reassortant analysis, biotic and molecular characterization, and development and the application of molecular approaches for investigating their identity and distribution on a global basis. The website, GEMINI DETECTive (http://www.ipmnet.org/GEMINI) has been established that permits begomovirus identification based upon sequence comparisons of the ‘core’ or middle region of the coat protein gene (core Cp). Universal primers that target a 576-579 bp fragment of the coat protein gene of all begomoviruses, viral identity can be predicted from the sequence using the BLAST program at the site to compare an unknown sequence to a suite of begomovirus reference sequences representing well-characterized begomoviruses and field isolates from different plants hosts, worldwide. General features of Begomoviruses, a global distribution map, and degenerate primers and PCR conditions are presented. Individual pages providing relevant information about recognized begomovirus species can be accessed through a link to the BLAST output, or can be accessed through the begomovirus ‘list’ page. Photographs illustrating symptom phenotypes in important hosts, host range information, and key references are also provided. This PCR-based approach provides the first diagnostic tool by which accurate molecular identification of begomoviruses can be achieved.

Variation Within the B.tabaci Group In Relation to Begomovirus Epidemiology. Geminiviral pathogens have also evolved a highly dependent relationship between their host plant and the whitefly vector. Work in our lab has demonstrated a surprising degree of biotic and genetic variation within B. tabaci, yet members of the taxon are considered a single species. Certain aspects of variation between B. tabaci ‘types’ (previously, races, strains, biotypes) may directly influence vector-mediated dispersal of geminiviruses, thereby, potentially influencing disease epidemiology, and consequently the evolution of begomoviruses. Along these lines we have pursued a critical examination of morphological, biological, and genetic polymorphisms for a suite of B. tabaci from different hosts and geographic sites, worldwide. Results collectively indicate that B. tabaci may constitute a group of sibling species that cannot be by differential morphological characters. To investigate the influence of distinct vector ‘types’ on the epidemiology of begomoviruses, we are developing approaches for identifying, and thereby, tracking B. tabaci variants through molecular sequence analysis. We have recently demonstrated that sequences of the mitochondria cytochrome oxidase gene (COI) accurately reflect biogeographic relationships of the variants examined. Future work will involve the correlation of COI phylotaxonomic predictions with those of relevant nuclear gene sequences.

Virus-Vector Specificity. The whitefly, Bemisia tabaci (Genn.) is the exclusive vector of begomoviruses, worldwide. Variants of this whitefly vector generally have moderate to broad host ranges, while the viruses they transmit are characterized by moderate to narrow host capabilities. Although the basis for the specificity between begomoviruses and their whitefly vector is not well understood, with respect to vector-mediated virus transmission, begomoviruses and B. tabaci exemplify a co-evolved complex. Begomoviruses are transmitted in a persistent, circulative manner by B. tabaci, and the viral nucleocapsid is thought to constitute the sole viral determinant of transmission. However, evidence suggests that several whitefly proteins may interact with viral capsid (virions), collectively, constituting ‘the transmission pathway’ that confers virus-vector specificity. Elucidating the cellular and molecular interactions and understanding the precise basis for the specificity underlying whitefly-mediated begomoirus transmission will enhance the fundamental understanding of complex interactions occuring between ‘organisms’ from three distinct kingdoms, and further, may lead disease control by targeting key of sites of specificity in the pathway to disrupt virus transmission.

Select Works and Publications

Websites

Brown, J. K. and S. D. Wyatt. 1998. GEMINIDETECTive Interactive WEB SITE: http://www.ipmnet.org/GEMINI/

Book Chapters, Compendia, and Proceedings

Brown, J.K. 1990. An update on the whitefly-transmitted geminiviruses in the Americas and the Caribbean Basin. FAO Plant Prot. Bull. 39:5-23.

Brown, J.K. and J. Bird. 1992. Whitefly-transmitted geminiviruses in the Americas and the Caribbean Basin: past and present. Plant Dis. 76:220-225.

Brown, J.K. 1992. Virus diseases of cotton. Pages 275-330 in: Cotton Diseases. R. J. Hillocks, ed. Commonwealth Agricultural Bureaux International, Oxon, United Kingdom. 415 pp.

Brown, J. K. 1994. The Status of Bemisia tabaci Genn. as a pest and vector in world agroecosystems. FAO Plant Prot. Bull. 42: 3-32.

Brown, J. K., D. Frohlich and R. Rosell, 1995. The Sweetpotato/Silverleaf Whiteflies: Biotypes of Bemisia tabaci Genn., or a Species Complex? Ann. Rev. Entomology 40: 511-534.

Brown, J. K. 1996. Chapter 5 in: Molecular Biology and Epidemiolgy of Subgroup III, Geminiviridae. Plant-Microbe Interactions Review Series, G. Stacey and N. Keen, (eds) Chapman and Hall, pp 125-195.

Brown, J. K. 1997. Viruses of cucurbits. In: Compendium of Cucurbit Viruses, American Phytopathological Society, St. Paul MN.

Brown, J. K. 1998. Plant Virus and MLO-like Diseases of Cotton In: Cotton Compendium. American Phytopathological Society, St. Paul MN (in press).

Journal Publications

Begomoviruses

Brown, J.K. and M.R. Nelson. 1984. Geminate particles associated with cotton leaf crumple disease in Arizona. Phytopathology 74:987-990.

Brown, J.K. and M.R. Nelson. 1986. Whitefly-borne viruses of melons and lettuce in Arizona. Phytopathology 76:236-239.

Brown, J.K., M.R Nelson, and R.C. Lambe. 1986. Cotton leaf crumple virus transmitted from naturally infected bean from Mexico. Plant Dis. 70:981.

Brown, J.K., J.D. Mihail, and M.R. Nelson. 1987. The effects of cotton leaf crumple virus on cotton inoculated at different growth stages. Plant Dis. 71:699-703.

Brown, J.K. and M.R. Nelson. 1987. Host range and vector relationships of cotton leaf crumple virus. Plant Dis. 71:522-524.

Brown J.K and M.R Nelson. 1988. Transmission, host range, and virus-vector relationships of chino del tomate virus (CdTV), a whitefly-transmitted geminivirus from Sinaloa. Plant Dis. 72:866-869.

Brown, J.K. and M.R. Nelson. 1989. Characterization of watermelon curly mottle virus, a geminivirus distinct from squash leaf curl virus. Ann. Appl. Biol. 115:243-252.

Brown, J.K., M.A. Chapman and M.R. Nelson. 1989. Disease of common bean caused by a whitefly-transmitted geminivirus. Plant Dis. 73:81.

Brown, J.K. and B.T. Poulos. 1990. Serrano golden mosaic virus: a new whitefly-transmitted geminivirus of pepper and tomato in the U.S. and Mexico. Plant Dis. 74:720.

Swanson, M. M., J. K. Brown, B. T. Poulos, and B. D. Harrison. 1992. Genome affinities and epitope profiles of whitefly-transmitted geminiviruses from the Americas. Ann. appl. Biol. 121:285-296.

Torres-Pacheco, I., J. A. Garzon-Tiznado, J. K. Brown, A. Becerra-Flora, and R. Rivera-Bustamante. 1996. Detection and distribution of geminiviruses in Mexico and the southern United States. Phytopathology 86: 1186-1192.

Wyatt, S. D., and J. K. Brown. 1996. Detection of subgroup III geminivirus isolates in leaf extracts by degenerate primers and polymerase chain reaction. Phytopathology 86: 1288-1293.

Salvucci, M., Rosell, R. C., and Brown, J. K. 1998. Uptake and metabolism of leaf proteins by the silverleaf whitefly. Archives of Insect Biochemistry and Physiology 39:155-165.

Brown, J.K., T. M. Perring, A.D. Cooper, I. D. Bedford, and P. G. Markham. 1999. Genetic analysis of Bemisia (Homoptera: Aleyrodidae) populations by isoelectric focusing electrophoresis. Biochemical Genetics (submitted).

Idris, A. M. and J. K. Brown. 1998. Sinaloa tomato leaf curl geminivirus: biological and molecular evidence for a new subgroup III virus. Phytopathology 88: 648-657.

Brown, J. K., K. M. Orstrow, and D. C. Stenger. 1999. Biotic, molecular, and phylogenetic characterization of bean calico mosaic virus, a distinct Begomovirus species with affiliation in the squash leaf curl virus cluster. Phytopathology (in press).

Brown, J. K., I. Torres-Jerez, A. M. Idris, G. K. Banks, and S. D. Wyatt. 1999. The core region of the coat protein gene as a molecular marker for identification and phylogenetic analysis of whitefly-transmitted geminiviruses. Phytopathology: (submitted).

Idris, A.M., H. Lee, and J. K. Brown. 1999. First report of chino del tomate and pepper huasteco geminiviruses in greenhouse-grown tomato in Sonora, Mexico. Plant Disease (in press).

Idris, A. M., G. Rivas-Platero, I. Torres-Jerez, and J.K. Brown. 1999. First report of Sinaloa tomato leaf curl virus in Costa Rica. Plant Disease: (in press).

McGrath, P.F., I. Torres-Jerez, and J. K. Brown. 1999. Host range, vector transmission, and identification by core coat protein gene analysis of three begomoviruses of tobacco from Mexico. European Journal of Plant Pathology (submitted).

Paximadis, M. , A.M. Idris, I. Torres-Jerez, A. Villarreal, M.E.C. Rey, and J.K. Brown. 1999. Characterization of geminiviruses of tobacco in the Old and New World. Archives of Virology: (in press).

Variation Within the Whitefly Vector

Costa, H.S., J.K. Brown, and D.N.Byrne. 1991. Host plant selection by the whitefly, Bemisia tabaci (Genn.) (Homoptera: Aleyrodidae) under greenhouse conditions. J. Appl. Entomol. 112:146-152.

Costa, H.S., J.K. Brown, and D.N. Byrne. 1991. Life history traits of the whitefly Bemisia tabaci (Genn.) (Homoptera: Aleyrodidae) on six virus-infected or healthy plant species. Environ. Entomol. 20: 1102-1107.

Costa, H.S., and J.K. Brown. 1991. Variation in biological characteristics and in esterase patterns among populations of Bemisia tabaci (Genn.) and the association of one population with silverleaf symptom development. Entomol. exp. appl. 61:211-219.

Costa, H. S., J. K. Brown, S. Sivasupramaniam, and J. Bird. 1993. Regional distribution, insecticide resistance, and reciprocal crosses between the `A' and `B' biotypes of Bemisia tabaci. Insect Sci. and Applic. 14:127-138.

Bedford, I.D., P.G. Markham, J.K. Brown and R.C. Rosell. 1994. Geminivirus trnsmission and biological characterization of whitefly (Bemisia tabaci) biotypes from different world regions. Ann. appl. Biol. 125: 311-325.

Coats, S. A., J. K. Brown, and D. L. Hendrix. 1994. Biochemical characterization of biotype-specific esterases in the whitefly Bemisia tabaci Genn. (Homoptera:Aleyrodidae). Insect Biochem. Mol. Biol. 24: 723-728.

Brown, J. K., S. Coats, I . D. Bedford, and P. G. Markham, J. Bird, and D. R. Frohlich. 1995. Characterization and distribution of esterase electromorphs in the whitefly, Bemisia tabaci (Genn.) (Homoptera:Aleyrodidae). Biochemical Genetics: 33: 205-214.

Costa, H.S., D.M. Wescot, D.E. Ullman, R. Rosell, J. K Brown, and M.W. Johnson. 1995. Morphological variation in Bemisa endosymbionts. Protoplasma: 189: 194-202.

Costa, H. S., D. M. Wescot, D. E. Ullman, R. C. Rosell, J.K Brown, and M.W. Johnson. 1996. Virus-like particles in the mycetocytes of the sweetpotato whitefly, Bemisia tabaci (Homoptera: Aleyrodidae). J. Invert. Pathology: 67: 183-186.

Rosell, R. C., I. D. Bedford, D. R. Frohlich, R. J. Gill, P. G. Markham, and J. K. Brown. 1997. Analyses of morphological variation in distinct populations of Bemisia tabaci. Ann. Entomol. Soc. of Am. 90: 575-589.

Frohlich, D., I. Torres-Jerez, I. D. Bedford, P. G. Markham, and J. K. Brown. 1999. A phylogeographic analysis of the Bemisia tabaci species complex based on mitochondrial DNA markers. Molecular Ecology (submitted).

Toward Whitefly or Begomovirus Control

Wilson, F. D., J.K. Brown, G.D. and Butler, Jr. 1990. Reaction of cotton cultivars and lines to cotton leaf crumple virus. J. of the Az.-Nev. Acad. Sci. 23:7-10.

Wilson, F. D., and J.K. Brown. 1991. Inheritance of resistance to cotton leaf crumple virus in cotton. J. of Heredity 82:508-509.

Anthony, N., J. K. Brown, P. G. Markham, and R. H. ffrench-Constant. 1995. Molecular analysis of cyclodiene resistance-associated mutations among populations of the sweetpotato whitefly Bemisia tabaci . Pestic. Biochem. & Physiology 51: 220-228.

Thomas, J. C., D. G. Adams, C.L. Nessler, J. K. Brown, and H. J. Bohnert. 1995. Tryptophan decarboxylase, tryptamine, and reproduction of the whitefly. Plant Physiol 109: 717-720.

Thomas, J. C., D. G. Adams, V. D. Keppenne, C. C. Wasmann, J. K. Brown, M. R. Kanost, and H. J. Bohnert. 1995. Protease inhibitors of Manduca sexta expressed in transgenic cotton. Plant Cell Reports 14: 758-762.

Thomas, J. C., D. G. Adams, C.L. Nessler, J. K. Brown, and H. J. Bohnert. 1995. Tryptophan decarboxylase, tryptamine, and reproduction of the whitefly. Plant Physiol 109: 717-720.

Anthony, N. M., J.K.Brown, R. Feyereisen, and R. H. ffrench-Constant. 1997. Diagnosis and characterization of insecticide insensitive acetylcholinesterase in three populations of the sweetpotato whitefly Bemisia tabaci. Pesticide Biochemistry 52: 39-46.

Virus-Vector Specificity

Rosell, R., J. E. Lichty, and J. K. Brown. 1995. Ultrastructure of the mouthparts of adult sweetpotato whitefly, Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae). Int. J. of Insect Morphol. & Embryol. 24: 297-306.

Rosell, R. C., I. Torres-Jerez, and J. K. Brown. 1999. Temporal pathway of geminivirus in whitefly extracts, saliva, hemolymph and honeydew. Phytopathology: (in press).