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United States Department of Agriculture

Agricultural Research Service

C Thomas Chao


 Plant Genetic Resources Unit


630 W. North St., Geneva, NY14456

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.

Publications 2006-2016

Volk, G.M., M.M. Jenderek, and C.T. Chao. 2016. Prioritization of Malus accessions for collection cryopreservation at the USDA-ARS national Center for Genetic Resources Preservation. Acta Hort. (In press).

Migicovsky Z., K.M. Gardner, D. Money, J. Sawler, J.S. Bloom, P. Moffett, C.T. Chao, H. Schwaninger, G. Fazio, G.-Y. Zhong, and S. Myles. 2016. Genome to phenome mapping in apple using historical data. Plant Genome (In press; available online 2/23/2016; 114 pages).\

Janisiewicz, W.J., Nichols, G. Bauchan, C.T. Chao, and W.M. Jurick. 2016. Wound responses of wild apples suggest multiple resistance mechanism against blue mold. Postharvest Biology and Technology 171:132-140.

Volk, G.M., A.D. Henk, A. Baldo, G. Fazio, C.T. Chao, and C.M. Richards. 2015. Chloroplast heterogeneity and historical admixture within the genus Malus. Amer. J. Botany 102(7):1-11.

Volk M., C.T. Chao, J. Norelli, S.K. Brown, G. Fazio, C. Peace, J. McFerson, G.-Y. Zhong, and P. Bretting. 2015. The vulnerability of U.S. apple genetic resources. Genet. Res. Crop Evol. 62:765-794. DOI 10.1007/s10722-014-0194-2.

Fazio, G., C.T. Chao, P.L. Forsline, C. Richards, and G. Volk. 2014. Tree and root architecture of Malus sieversii seedlings for rootstock breeding. Proc. Xth ISHS on Integrating Canopy, Rootstock and Environmental Physiology in Orchard Systems. Acta Hort. 1058:585-594.

Volk G.M., A.D. Henk, C.M. Richards, P.L. Forsline, and C.T. Chao. 2013. Malus sieversii: a diverse Central Asian apple species. HortScience 48(12):1440-1444.

Gross, B.L., G.M. Volk, C.M. Richards, P.A. Reeves, A.D. Henk, P.L. Forsline, A. Szewc-McFadden, G. Fazio, and C.T. Chao. 2013. Diversity captured in the USDA-ARS National Plant Germplasm System apple core collection. J. Amer. Soc. Hort. Sci. 138(5):375-381.

Gross, B.L., G.M. Volk, C.M. Richards, P.L. Forsline, G. Fazio, and C.T. Chao. 2012. Identification of “duplicate” accessions within the USDA-ARS National Plant Germplasm System Malus 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 crops 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.

Pillitteri, L.J., I. Bertling, T. Khuong, C.T. Chao and C.J. Lovatt. 2010. Foliar-applied Tryptophan increase total yield and fruit size of Citrus reticulate (Blanco) cv. Fina Sodea Clementine. XI International Symposium on Plant Bioregulators in Fruit Production. Bologna, Italy. Acta Horticulturae 884:729-736.

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.

Chao, C.T. and R.R. Krueger. 2008. Date Palm, in “The Encyclopedia of Fruits and Nuts”, Editor, J. Janick. CAB International, Wallingford, Oxon, UK.

Paull, R.R. and C.T. Chao. 2008. Avocado, in “The Encyclopedia of Fruits and Nuts”, Editor, J. Janick. CAB International, Wallingford, Oxon, UK.

Fang, J.G., J. Chen, R.J. Henny, and C.T. Chao. 2007. Genetic relatedness of ornamental Ficus species and cultivars analyzed by amplified fragment length polymorphism markers. J. Amer. Soc. Hort. Sci. 132(6):807-81.

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

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

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

Chao, C.T. and C.J. Lovatt. 2006. Effects of GA3 concentration and application time on fruit set and fruit size of Clementine mandarin in California. Acta Horticulturae 727:227-237.

Fang, J., T. Twito, Z. Zhang, and C.T. Chao. 2006. Genetic diversity of fruiting-mei (Prunus mume et Zucc.) accessions revealed by AFLP and SNP markers. Genome 49:1256-1264.

Fang, J., G. Tao, and C.T. Chao. 2006. The genetic diversity of mei, apricot, plum, and peach revealed by AFLP. J. Hort. Sci. & Biotechnology 81:898-902.

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.

Fang, J., P.S. Devanand, and C.T. Chao. 2006. Practical strategy of single-nucleotide-polymorphism discovery in fruiting-mei (Prunus mume et Zucc.) from AFLP fragments. Plant Molecular Biology Reporter 27:227-239.

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.


Last Modified: 10/3/2016
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