in The Department of Plant Sciences

College of Agriculture and Life Sciences, Forbes Building 303,
P.O. Box 210036,
Tucson AZ 85721-0036
(520) 621-1977, FAX (520) 621-7186

Dr. Marc Orbach

Associate Professor
Divsion of Plant Pathology & Microbiology
College of Agriculture and Life Sciences
Ph.D. (1988), Stanford University 

e-mail: orbachmj@ag.arizona.edu

Area of Interest:
Molecular genetics of fungal cultivar specificity genes in Magnaporthe grisea.

Research Goals:
My research program uses Magnaporthe grisea, the fungal pathogen responsible for the rice blast disease, as a model system to study host-pathogen interactions at the molecular and biochemical level. This pathogen, like many other plant pathogens, interacts with its host in a gene-for-gene manner, where host resistance is induced when the plant contains a resistance gene and the pathogen, a corresponding avirulence gene. The main focus of our program is to understand what the signals between the pathogen and its host are, that dictate whether the host is able to mount a resistance response. Genetic analysis of M. grisea have identified several avirulence genes that determine what their products are and how these products interact with host plants to induce host defenses. We are also interested in questions of genome stability and the generation of genetic variability in fungi. These questions are of significance in M. grisea because of the apparent ability of this pathogen to rapidly overcome host resistance in the field. We are addressing these questions by studying genome variation in M. grisea at the whole genome level using electrophoretic karyotyping methods. We are also specifically analyzing the role that a transposable element may play in genome variation and the high rate of mutation observed at some loci. 


Mycology 427 laboratory

Most Recent Publications:

Hamer L, HQ Pan, K. Adachi, M.J. Orbach, A. Page, L. Ramamurthy L and J.P. Woessner. 2001.  Regions of microsynteny in Magnaporthe grisea and Neurospora crassa. Fungal Genet. and Biol.
 33: 137-143.

    Orbach, M.J., L. Farrall, J.A. Sweigard, F.G. Chumley, and B. Valent.  2000.  A telomeric avirulence gene determines efficacy for the rice blast resistance gene Pi-ta.   Plant Cell 12: 2019-2032

    Mandel, M.A., G.G. Grace, K.I. Orsborn, F. Schafer, J.W. Murphy, M.J. Orbach, and J.N. Galgiani.  2000. The Cryptococcus neoformans gene DHA1 encodes an antigen that elicits a delayed-type hypersensitivity reaction in immune mice. Infect. Immun. 68: 6196-6201

    Aboudeh, R.O., M.J. Orbach, M.A. Mandel, A. Das and J.N.Galgiani. 2000. Genetic Transformation of Coccidioides immitis Facilitated by Agrobacterium tumefaciens. Journal of Infection and Disease 181:2106-2110.

    Kang, S., E. Mullins, T.M. Dezwann, and M.J. Orbach. 2000. Pathogenesis and Genome Organization of the Rice Blast Fungus. In: Fungal Pathology. J.W. Kronstad (ed), Kluwer Academic Publishers. Dordrecht, The Netherlands. 41 pages. 

    Dioh, W., D. Tharreau, J.-L. Notteghem, M. Orbach and M.-H. Lebrun. 2000. Mapping of avirulence genes in the rice blast fungus, Magnaporthe grisea. with RFLP and RAPD markers. Mol. Plant-Microbe Interact. 13:217-227

    Woo, H.-H., M.J. Orbach, A. M. Hirsch, and M.C. Hawes. 1999. Meristem-localized inducible expression of a UDP-glycosyltransferase gene is essential for growth and development in pea and alfalfa. Plant Cell 11: 2303-2316

    Peng, T., K.I. Orsborn, M.J. Orbach, and J.N. Galgiani. 1999. Proline-rich vaccine candidate antigen of Coccidioides immitis: Conservation among isolates and differential expression with spherule maturation. J. Infect. Dis. 179:518-521

    Mandel, M.A.., W.W. Crouch, U.P. Gunawardena, T.M. Harper, and M.J. Orbach. 1997. Physical mapping of the Magnaporthe grisea AVR1-MARA gene reveals the virulent allele contains two deletions. Mol. Plant-Microbe Interact. 10:1102-1105.

    Diaz-Perez, S.V.,, W. Crouch,and M.J. Orbach. 1996. Construction and characterization of a Magnaporthe grisea bacterial artificial chromosome library.  Fungal Genetics and Biology 20:280-288. 

    Orbach, M.J., F.G.., Chumley, and B. Valent. 1996. Electrophoretic karyotypes of Magnaporthe grisea pathogens of diverse grasses.  Mol. Plant-Microbe Interact. 9:261-271. 

    Dioh, W., Tharreau, D., Gomez, R., Roumen, E., Orbach, M. J., Notteghem, J. L., and M.H. LeBrun. 1995. Mapping avirulence genes in the rice blast pathogen fungus Magnaporthe grisea.  Rice Genetics III 

    Orbach, M. J. 1994. A cosmid with a HyR marker for fungal library construction and screening. Gene 150:159-162. 

 For more information contact: 
Dr. Marc J. Orbach 
University of Arizona 
303 Forbes Building 
P.O. Box 210036 
Tucson, AZ 85721-0036 

Phone: (520)621-3764 
Fax: (520)621-7186

last updated: August 18, 2006
2004 The University of Arizona. All contents copyrighted. All rights reserved.