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United States Department of Agriculture

Agricultural Research Service

C Thomas Chao


Plant Genetic Resources Unit


630 W. North St., Geneva, NY 14456

315 787 2454 (office)

315 787 2339 (fax)



I am a horticulturist and curator for the national clonal germplasm collections of apples, cold-hardy grapes, and tart cherries of the PGRU, USDA-ARS at Geneva, NY.  The mission of the repository is to acquire, maintain, characterize and distribute the genetic resources of apple, grape and tart cherry germplasm.  There are over 9,000 accessions in the collection and it is the largest and most genetically diverse Malus collection in the world.  The collections include varieties, species, species hybrids, and wild collections from USA, Canada, Europe, Central Asia, Turkey, China and other regions.  We support and cooperate on many research projects by providing budwood, DNA samples, leaf, fruit samples, and pollen nationally and internationally.  We also carry out research on characterization of germplasm in our collections.



·        Ph.D. in Plant Breeding and Plant Genetics, University of Wisconsin-Madison, Madison, WI.

·    M.S. in Horticulture, University of California-Davis, Davis, CA.

·    B.S. in Horticulture, Chinese Culture University, 1985, Taipei, Taiwan.


Professional Experience

·         Horticulturist and Curator, 2011 – present, Plant Genetic Resources Unit, USDA-ARS, Geneva, NY.

·        Horticulturist, 2009-2010, Sunkist Growers, Fontana, CA.

·    President, CEO and Director, 2006-2008, Thermal Plaza Nursery, Thermal, CA.

·        Assistant and Associate Extension Horticulturist, 1998-2006, Department of Botany and Plant Sciences, University of California-Riverside, Riverside, CA. 

·       Visiting Postdoctoral Scholar, 1995-1998, Department of Pomology, University of California-Davis, Davis, CA.


Selected Publications

·         Gross, B.L., G.M. Volk, C.M. Richards, P.L. Forsline, G. Fazio, and C.T. Chao. Identification of “duplicate” accessions within the USDA-ARS National Plant Germplasm System Malus collection. Gross et al.-------                 J. Amer. Soc. Hort. Sci. 137(5):333-342.

·         Chao, C.T., T. Khuong, Y. Zheng, and C.J. Lovatt. 2011. Response of evergreen perennial tree crop to gibberellic acid is crop load-dependent. I: GA3 increase the yield of commercially valuable ‘Nules’ Clementine mandarin fruit only in the off-crop year of an alternate bearing orchard. Scientia Horticulturae 130:753-761.

·         Chao, C.T. and C.J. Lovatt. 2010. Foliar-applied 3,5,6-Trichloro-2-Pyridyloxyacetic Acid increases yield of commercially valuable large fruit of ‘Fina Sodea’ Clementine mandarin.  XI International Symposium on Plant Bioregulators in Fruit Production.  Bologna, Italy. Acta Horticulturae 884:433-440.

·         Song, C., J. Fang, X. Li, H. Liu, and C.T. Chao. 2009. Identification and characterization of 27 conserved microRNAs in citrus. Planta 230(4):671-685.

·         Fang, J.G. and C.T. Chao. 2007. Methylation-sensitive amplification polymorphism in date palms (Phoenix dactylifera L.) and their off-shoots. Plant Biology 9:526-533. 

·         Chao, C.T. and R.R. Krueger. 2007. The dates (Phoenix dactylifera L.): Overview of biology, cultivars and uses. HortScience 42:1077-1082.

·         Fang, J., C.T. Chao, P.A. Roberts, and J.D. Ehlers. 2007. Genetic diversity of cowpea (Vigna unguiculata L. Walp.) in four West African and USA breeding programs as determined by AFLP analysis. Genet. Resour. & Crop Evol. 54(6):1197-1209.

·         Elhoumaizi, M.A., P.S. Devanand, J. Fang, and C.T. Chao. 2006. Confirmation of ‘Medjool’ date as a landrace variety through genetic analysis of ‘Medjool’ accessions in Morocco. J. Amer. Soc. Hort. Sci. 131(3):403-407.

·         Chen, J., R.J. Henny, P.S. Devanand, C.T. Chao. 2006. AFLP marker analysis of nephthytis (Syngonium podophyllum Schott) selected from somaclonal variants. Plant Cell Report 24: 743-749.

·         Chao, C.T., J.J. Fang and P.S. Devanand. 2005. Long distance pollen flow in mandarin orchards determined by AFLP markers - Implication for seedless mandarin production. J. Amer. Soc. Hort. Sci. 130(3):374-380.

·         El-Assar, A.M., R.R. Krueger, P.S. Devanand, and C.T. Chao. 2005. Genetic analysis of Egyptian date (Phoenix dactylifera L.) accessions using AFLP markers. Genet. Resour. & Crop Evol. 52:601-607.

·         Chen, J.J., P.S. Devanand, D.J. Norman, R.J. Henny, and C.T. Chao. 2004. Genetic relationships of Aglaonema species and cultivars inferred from AFLP markers. Annals of Botany 93(2):157-166.

·         Chao, C.T., D.E. Parfitt, L. Ferguson, C. Kallsen, and J. Maranto. 2003. Genetic analysis of phenological traits of pistachio (Pistacia vera L.). Euphytica 129(3):345-349.

·         Cao, B.R. and C.T. Chao. 2002. Identification of date palm cultivars in California using AFLP markers. HortScience 37(6):966-968.

·         Chao, C.T., T.J. Michailides, and D.E. Parfitt. 2001.  Alternaria late blight (Alternaria alternata) resistance in pistachio (Pistacia vera) and selection for resistant genotypes. J. Amer. Soc. Hort. Sci. 126(4):481-485.

·         Chao, C.T., K.A.K. Moldenhauer, and A.H. Ellingboe. 1999. Genetic analysis of resistance/susceptibility in individual F3 families of rice against strains of Magnaporthe grisea containing different genes for avirulence. Euphytica 109(3):183-190.

·         Chao, C.T. and A.H. Ellingboe. 1997. Genetic analysis of avirulence/virulence of an isolate of Magnaporthe grisea from a rice field in Texas. Phytopathology 87(1):71-76.

·         Chao, C. T. and A. H. Ellingboe. 1991. Selection for mating competence in Magnaporthe grisea pathogenic to rice. Can. J. Bot. 69: 2130-2134.

Last Modified: 2/13/2013
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