Ryan Contreras

Assistant Professor
Send an Email

Office: 541-737-5462

Agricultural & Life Sciences

Agricultural & Life Sciences 4031

2750 SW Campus Way

2750 SW Campus Way
Corvallis, OR 97331
Do you accept grad students?: 
I accept graduate students for Horticulture

My research program involves several areas of ornamental plant breeding and cultivar development. Of primary interest is the development of sterile forms of nonnative invasive species that are of economic importance to Oregon growers. Primary techniques to achieve sterility/reduced fertility include develoment of triploids using ploidy manipulation, as well as mutagenesis by exposing seeds or meristems to physical and chemical mutagens.

Another area of focus is to identify cultivars or selections that have increased insect and disease resistance. My program conducts basic research in traditional genetics, cytogenetics, and molecular cytogenetics to support the applied breeding program with the goal of developing plants that are attractive to consumers and easy for growers to produce.

Graduate Students


Jason Lattier - Ph.D. Student  

  • Developing a linkage map in Syringa.
  • Hibiscus syriacus breeding to develop sterile cultivars and investigation of heritability of various floral traits
  • Cytology and flow cytometry of selected woody nursery crops

Kim Shearer-Lattier - M.Sc. Student

  • Evaluating M1 & M2 populations of Galtonia candicans 
  • Genome size and ploidy level survey in Acer
  • Interspecific hybridization in Penstemon to improve adaptibility to cultivation


Joseph Rothleutner - M.Sc. - Genome Sizing and Fire Blight Resistance Screening in Cotoneaster.  Current Position:  Director of Horticulture at the Lincoln Park Zoo in Chicago

I accept graduate students for Horticulture

Profile Field Tabs

Affiliated with: 
Courses Taught: 

HORT 226. Landscape Plant Materials I:  Deciduous Hardwoods and Conifers. Fall. 4 credits

HORT 226e.  Landscape Plant Materials I:  Deciduous Hardwoods and Conifers.  Fall - Online.  4 credits

HORT 228. Landscape Plant Materials II:  Spring Flowering Trees and Shrubs. Spring. 4 credits

HORT 228e. Landscape Plant Materials II:  Spring Flowering Trees and Shrubs. Spring - Online. 4 credits

HORT 301. The Biology of Horticulture. Fall. 3 credits

HORT 301e.  The Biology of Horticulture.  Fall & Spring - Online.  3 credits

HORT 311.  Plant Propagation.  Winter.  4 credits.

HORT 311e.  Plant Propagation.  Fall & Winter - Online

201.  4 credits.

Proceedings and Conference Presentations: 

Contreras, R.N.  201X.  Ornamental Plant Breeding at Oregon State University.  Combined Proceedings of the International Plant Propagators' Society (Accepted). 

Contreras, R.N., J. Rothleutner, and V. Stockwell.  201X.  Breeding for fire blight resistance and sterility in Cotoneaster.  ActaHort. Proceedings of the 13th ISHS Congress on Fire Blight (Accepted).

Contreras, R.N., M. Friddle, and J.D. Lattier.  2013.  Relative fertility and ploidy levels of selected rose of sharon cultivars.  Proc. 58th Ann. SNA Res. Conf.  58:232-236.  

Rothleutner, J.J., R.N. Contreras, and V. Stockwell.  2012.  Evaluation of fire blight resistance of 31 species of Cotoneaster.  Proc. 57th Ann. SNA Res. Conf. 57:276-278.

Contreras, R.N. and J.M. Ruter. 2010. Induced polyploidy in Japanese cedar. Proc. 55th Ann. SNA Res. Conf. 55:25-29.

Contreras, R.N. and J.M. Ruter. 2008. Preliminary efforts to induce polyploidy in Cryptomeria japonica. Proc. 53rd Ann. SNA Res. Conf. 53:159-161.

Contreras, R.N. and J.M. Ruter. 2007. New Callicarpa species with breeding potential. Proc. 52nd Ann. SNA Res. Conf. 52:327-329. 

Contreras, R.N., T.G. Ranney, S.P. Tallury and S.R. Milla. 2005. Using molecular  markers to investigate parentage of azaleodendron hybrids. 2005. Proc. 50th Ann. SNA Res. Conf. 50:632-635.

Contreras, R.N. and T.G. Ranney. 2004. New opportunities for breeding allopolyploid azaleodendrons. Proc. 49th Ann. SNA Res. Conf. 49:552-554.

Faculty Type: 
OSU Main Campus