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Assistant Research Scientist – Plant Pathology Affiliate Professor Department of Agricultural Sciences West Texas A&M University Texas AgriLife Research |
Education
PhD., (2008) in ‘Plant and Environmental Science’, Department of Plant Pathology and Microbiology at Rothamsted Research, Harpenden UK, (degree awarded by the University of Warwick, UK)
MSc., with distinction (2004) in ‘Plant Breeding and Biotechnology’ at The University of East Anglia and the John Innes Centre, Norwich, UK.
BSc. (Hons) in Biological Sciences majoring in Plant Sciences, The University of Leicester, UK.
Introduction
Polymyxa species, which vector many plant viruses, belong to a group known as the plasmodiophorids. Ten genera have been previously described in the plasmodiophorids, these include: Sorodiscus, Sorosphaera, Spongospora, Plasmodiophora, Polymyxa, Octomyxa, Ligniera, Membranosoras, Woronina,Tetramyxa and Maullinia. The genera within the plasmodiophorids encompass a diverse group of organisms. Some, such as Polymyxa, Spongospora and Plasmodiophora are obligate parasites of plants (cereals and sugar beet; potatoes and watercress; and brassicas respectively).Others such as Octomyxa, Sorodiscus and Woronina parasitize Oomycete hosts, whilst Maullinia ectocarpii is a parasite of filamentous brown algae. Spongospora, Plasmodiophora and Polymyxa have proved to be of importance agronomically as the causes of plant disease and as plant virus vectors. Spongospora subterranea (Wallroth) Lagerheim f. sp. subterranea Tomlinson causes powdery scab on potatoes as well as transmitting Potato mop top virus and S. subterranea (Wallroth) Lagerheim f. sp. nasturtii Tomlinson causes crook root in watercress as well as being the proposed vector of Watercress yellow spot virus. Plasmodiophora brassicae induces hypertrophy and hyperplasia causing clubroot of brassicas. In contrast, P. graminis does not appear to cause any deformity in its host. It does however transmit approximately 10-15 plant viruses to cereals such as wheat, barley, oats and rice. Polymyxa betae (the other only other specie in the genus), vectors the agronomically important Beet necrotic yellow vein virus, which causes Rhizomania or ‘root madness’in sugar beet, as well as a number of other viruses.
P. graminis appears to be ubiquitous and can be found all over the world including North America, South America, Sub-Saharan Africa, Europe and Asia. P. betae is
now found throughout the sugar beet growing regions of the world. Although frequently referred to as a parasite, to date no detrimental effects of root colonisation
by P. graminis on host plants has been demonstrated and the relationship should therefore be considered as commensalistic. In the case of P. betae, root necrosis is
often observed but it is not easy to separate this necrosis from that caused by the viruses that it transmits. This is in marked contrast to some of the other members of the plasmodiophorids.
Current Research
Beet necrotic yellow vein virus (BNYVV) and Beet soilborne mosaic virus (BSBMV) are the two species in the genus Benyvirus. Both are vectored by zoospores of the plasmodiophorid Polymyxa betae. BNYVV causes rhizomania, an extremely damaging root disease of sugar beet, but BSBMV is essentially nonpathogenic. It is not uncommon to find these two viruses in the same field, infecting the same plant. Strong, dominant, monogenic resistance is conferred against BNYVV (not P. betae or BSBMV) by the Rz1 resistance gene, but resistance-breaking (RB) stains of BNYVV have recently evolved. RB strains pose an immediate threat to sustainability of the US sugar beet industry. The goal of our research is to elucidate the manner in which host resistance, irrigation frequency and virus population composition interact to affect intraplant spread of RB BNYVV.
General Research Interests
- Epidemiology of Plasmodiophorid virus-vectors and the viruses they transmit
- Infection biology of Polymyxa species
- Phylogenetic relationships of Polymyxa species and their biological significance
Other Activities
- Election two years running as a student representative to the Staff-Student Committee for the Biological Sciences Department, University of Leicester, representing student views. Member of Post graduate training committee at University of East Anglia and Rothamsted Research
- Volunteering with the charity ‘Sense about Science’ which aims to combat the misrepresentation of science issues in the media
- Supervision of a 10 week undergraduate student summer project funded by the British Society for Plant Pathology teaching molecular biology skills.
Publications
Smith, M.J., Adams, M.J., Ward, E. (2011) Evidence that Polymyxa species may infect Arabidopsis thaliana. FEMS Microbiology Letters. (in press)
Yilmaz, Nazli D. Kutluk, Rebecca Lyons, Madeleine J. Smith, Michael J. Adams, and Kostya Kanyuka. 2010. Investigation of soilborne mosaic virus diseases transmitted by Polymyxa graminis in cereal production areas of the Anatolian part of Turkey. European Journal of Plant Pathology. (in press)
Smith, M.J., Ward E., Walsh J.A., Adams M.J. (2005) Occurrence and significance of the temperate ribotypes of Polymyxa graminis. In CM Rush, ed, The Sixth Symposium of the International Working Group on Plant Viruses with Fungal Vectors. American Society of Sugar Beet Technologists, Bologna, Italy, pp 104-106.
Useful Reviews
Rush, C. M., Liu, H. Y., Lewellen, R. T. and Acosta-Leal, R.(2006) The continuing saga of rhizomania of sugar beets in the United States. Plant Disease, 90,
4-15.
Rush, C. M. (2003) Ecology and epidemiology of Benyviruses and plasmodiophorid vectors. Annual Review of Phytopathology, 41, 567-592.
Kanyuka, K., Ward, E. and Adams, M., J. (2003) Polymyxa graminis and the cereal viruses it transmits: a research challenge. Molecular Plant Pathology, 4, 393-
406.
