My research program involves several areas of ornamental plant breeding and cultivar development. Of primary interest is the development of sterile forms of nonnative species that are of economic importance to Oregon growers to prevent escape from cultivation. 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.
We are also trying to develop new cultivars that have increased insect and disease resistance. We conduct fundamental research in traditional genetics, cytogenetics, molecular genetics, and genomics to support the applied breeding program with the goal of developing plants that are attractive to consumers, easy for growers to produce, and resilient in modern landscapes.
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. Growth and Development of Horticutural Crops. Fall. 3 credits
HORT 301e. Growth and Development of Horticutural Crops. Fall & Spring - Online. 3 credits
HORT 311. Plant Propagation. Winter. 4 credits
HORT 311e. Plant Propagation. Winter - Online. 4 credits
Project Leader - Ryan Contreras
Ph.D. Horticulture, The University of Georgia - Athens, Georgia - December 2009
M.S. Horticultural Science, North Carolina State University - Raleigh, North Carolina - June 2006
B.S. Horticultural Science, North Carolina State University - Raleigh, North Carolina - December 2002.
Associate Professor, Oregon State University, Department of Horticulture. 40% Teaching / 35% Research. September 2016 - current.
Assistant Professor, Oregon State University, Department of Horticulture. 40% Teaching / 35% Research. December 2009 - September 2016
Graduate Research Assistant, University of Georgia, Athens, Georgia, Department of Horticulture. 2006 - 2009
Graduate Research Assistant, North Carolina State University, Raleigh, Department of Horticultural Science. 2004 - 2006
Awards and Honors
2018 Oregon Association of Nurseries Distinguished Education Award
2018 Western Region Award for Excellence in College and University Teaching in the Food and Agricultural Sciences
2016 Oregon Association of Nurseries President’s Five Star Award
2015 R.M. Wade Award for Excellence in Teaching and Registry of Distinguished Teachers
2013 College of Agricultural Sciences Savery Outstanding Young Faculty Award
Research Assistant - Tyler Hoskins
Tyler is a native Oregonian who has degrees from Clackamas Community College, George Fox, and Virginia Tech. The latter is where he honed his expertise in managing water and nutrients in soilless substrates of nursery crops - earning his M.S. with former Oregon State professor, Jim Owen. Tyler expertly manages the growing operation for the breeding program from propagation, to containers, field production, irrigation, and fertilization.
Current Graduate Students
Kristin Neill - M.S. Student
Recurrent selection to improve fruit and landscape qualitities of evergreen huckleberry.
Interploidy and intersubgeneric hybridization in Cotoneaster.
Hsuan Chen - Ph.D. 2018 - Developing Tools for Hardy Hibiscus and Lilac Breeding: Quantile Regression, Cytogenetics, Interspecific Hybridization, Somatic Hybridization, and Marker-Trait Association
Jason Lattier - Ph.D. 2017 - Breeding and Genetics of Lilacs and Hardy Hibiscus. Current Position: Post Doctoral Researcher at the US National Arboretum. Beltsville, MD.
Justin Schulze - M.S. 2017 - Breeding, Production, and Morphophysiology among Cytotypes of Common and Portuguese Cherrylaurel. Current Position: Breeder and Horticulturist with Bailey Nurseries, Inc. at their PII location in Watkinsville, GA.
Kim Shearer - M.S. 2016 - Inducing and evaluating phenotypic and cytometric variation in landscape plants: Observations from Acer, Galtonia, and Penstemon. Current Position: Tree and Shrub Breeder at the Morton Arboretum, Chicago, IL.
Joseph Rothleutner - M.S. 2012 - Genome Sizing and Fire Blight Resistance Screening in Cotoneaster. Current Position: Director of Horticulture at the Lincoln Park Zoo, Chicago, IL
Undergraduate Researchers and Interns
Lena Wilhelm. Assessing ploidy variation of Berberis nervosa over its geographic distribution: preliminary observations from the collections of the OSU Herbarium.
Ty Seely. Analysis of pollen from 22x, 33x, 44x, and 22x+44x common cherrylaurels.
Patrice Woodworth. Ploidy analysis of seedlings dervied from 2x+4x Hydrangea macrophylla.
Gwyn Alanko: Ploidy analysis of maple seedlings derived from tetraploid parents.
Sawyer Hurd: Intern and assistant on mockorange breeding to evaluate fragrance, flowering, and form among newly developed hybrids
Jon Dempster: Fertility and morphological observations of 2x, 3x, and 4x crabapples including 'Prairiefire' and its polyploid derivatives.
Aleen Haddad: Genome size analysis in Acer: Comparing methods of sample handling and preparation
Rebecca Reeve: In vivo polyploidization of Hibiscus syriacus using diffferent mitotic inhibitors and application techniques
Geena Quinones: Non-targeted mutagenesis of Carpenteria californica using varying rates of gamma radiation
Morgan Chan: Field evaluation and herbarium voucher collection for 49 species of Cotoneaster
Tucker Doyle: In situ chromosome doubling of four Oregon native plants of varying growth forms
Tiffany Pham: In vitro polyploidization of Hydrangea macrophylla
Keith Lukowski: Mapping the woody flora of Oregon State University
Coral Cummings: Viability and longevity of Prunus laurocerasus and P. lusitanica pollen under varying storage conditions
Imogene Hollis: Propagation and cataloguing newly received accessions for the Ornamental Plant Breeding Program
*Lattier, J.D., H. Chen, and R.N. Contreras. 2019. Variation in genome size, ploidy, stomata, and rDNA signals in althea (Hibiscus syriacus L.). J. Amer. Soc. Hort. Sci. 144(2):130-140.
Hoskins, T. and R.N. Contreras. 201X. Increasing rates of ethylmethane sulfonate reduced seed germination percent, occurrence of twin seedlings, and plant height of Sarcococca confusa. HortScience (Submitted).
Graebner, R.C., H. Chen, R.N. Contreras, K.G. Haynes, and V.R. Sathuvalli. 2019. Identication of a high frequency of triploid potatoes from tetraploid x diploid crosses. HortScience (Accepted).
Vining, K.J., I. Pandelova, K. Hummer, N. Bassil, R.N. Contreras, K. Neill, H. Chen, A.N. Parrish, and B.M. Lange. Genetic diversity survey of Mentha aquatica L. and Mentha suaveolens Ehrh., mint crop ancestors. Genetic Resources and Crop Evolution 66(4):825-845.
*Chen, H., L. Xue, T. Li, and R.N. Contreras. 2019. Quantile regression facilitates simultaneous selection of negatively correlated floral traits among BC1F1 progeny of the male fertile hybrid cultivars Lohengrin and Resi (Hibiscus syriacus x H. paramutabilis). J. Amer. Soc. Hort. Sci. 144(1):70-76.
Contreras, R.N. and K. Shearer. 2018. Genome size, ploidy, and base composition of wild and cultivated Acer. J. Amer. Soc. Hort. Sci. 143(6):470-485. https://doi.org/10.21273/JASHS04541-18
*Lattier, J.D. and R.N. Contreras. 2017. Ploidy and genome size in lilac species, cultivars, and interploid hybrids. J. Amer. Soc. Hort. Sci. 142(5):355–366. doi: 10.21273/JASHS04189-17
*Lattier, J.D. and R.N. Contreras. 2017. Intraspecific, interspecific, and interseries cross-compatibility in lilac. J. Amer. Soc. Hort. Sci. 142(4):279-288. (JASHS cover).
*Lattier, J.D., H. Chen, and R.N. Contreras. 2017. Improved method for enzyme digestion of root tips for cytology. HortScience 52(7):1029-1032.
*Schulze, J.A., J.D. Lattier, and R.N. Contreras. 2017. In vitro germination of immature Prunus lusitanica seed. HortScience 52(8):1122-1124.
*Schulze, J.A. and R.N. Contreras. 2017. In vivo chromosome doubling of Prunus lusitanica and preliminary morphological observations. HortScience. 52(3):332-337.
*Schulze, J.A., R.N. Contreras, and C.F. Scagel. 2017. Comparing vegetative propagation of two ‘Schipkaensis’ cherrylaurel ploidy levels. HortTechnology 27(1):69-72.
Contreras, R.N. and L. Meneghelli. 2016. In vitro chromosome doubling of Prunus laurocerasus 'Otto Luyken' and 'Schipkaensis'. HortScience 51(12):1463-1466.
*Rothleutner, J.J., M.W. Friddle, and R.N. Contreras. 2016. Ploidy levels, relative genome sizes, and base pair composition in Cotoneaster. J. Amer. Soc. Hort. Sci. 141(5):457-466.
Contreras, R.N. and M.W. Friddle. 2015. ‘Oregon Snowflake’ flowering currant. HortScience 50(2):320-321.
*Rothleutner, J.J., R.N. Contreras, V.O. Stockwell, and J.S. Owen, Jr. 2014. Screening Cotoneaster for resistance to fire blight by artificial inoculation. HortScience 49(12):1480-1485.
Contreras, R.N., J.M. Ruter, and D.A. Knauft. 2014. Flower, fruit, and petiole color of american beautyberry (Callicarpa americana L.) are controlled by a single gene with three alleles. HortScience 49(4)422-424. (HortScience cover)
Contreras, R.N., J.M. Ruter, J.S. Owen, Jr., A. Heogh. 2013. Chlorophyll, carotenoid, and visual color rating of japanese-cedar grown in the southeastern United States. HortScience 48(12):1452-1456.
Schwartz, B.M., R.N. Contreras, K.R. Harris-Schultz, D.L. Heckart, J.B. Peake, and P.L. Raymer. 2013. Discovery and characterization of a turf-type triploid seashore paspalum. HortScience 48(12):1424-1427.
Schwartz, B.M., K.R. Harris-Schultz, R.N. Contreras, C.S. Hans, W.W. Hanna, and S.R. Milla-Lewis. 2013. Creation of artificial triploid and tetraploid centipedegrass using colchicine and breeding. Intl. Turfgrass Soc. Res. J. 12:327-334.
Contreras, R.N., J.S. Owen, W.W. Hanna, and B.M. Schwartz. 2013. Evaluation of seven complex Pennisetum spp. hybrids for container and landscape performance in the Pacific Northwest. HortTechnology 23(4):525-528.
Schwartz, B.M., K.R. Harris-Schultz, C.S. Hans, R.N. Contreras, and S.A. Jackson. 2013. Creation of hexaploid and octoploid zoysiagrass using colchicine and breeding. Crop Science 53:2218-2224.
Landgren, C., J.S. Owen, and R.N. Contreras. 2013. Evaluating soil and foliar fertilization of Abies nordmanniana under container and field production. Scandinavian J. For. Res. Published online 7 Jan 2013. doi:10.1080/02827581.2012.762939
Contreras, R.N., R. Golembiewski, J. Velez. 2013. Evaluation of study habits of plant identification students. HortTechnology 23(1):130-133.
Vining, K.J., R.N. Contreras, M. Ranik, and S.H. Strauss. 2012. Genetic methods for mitigating invasiveness of woody ornamental plants: research needs and opportunities. HortScience 47(9):1210-1216.
Contreras, R.N. 2012. A simple chromosome doubling technique is effective in several species of Cupressaceae. HortScience 47(6):712-714.
Contreras, R.N., J.M. Ruter, J. Conner, Y. Zeng, and P. Ozias-Akins. 2012. Interspecific hybridization in Tecoma Juss. (Bignoniaceae): Confirmation of hybridity using GISH and determination of 18s rDNA copy number using FISH in F1 hybrids. Genome 55(6):437-445. doi: 10.1139/g2012-030
Contreras, R.N., R. Determann, and M. Friddle. 2011. Differences in winter browning among japanese-cedar cultivars are not due to variation in ploidy levels. HortScience 46(11):1465-1467.
Contreras, R.N. and J.M. Ruter. 2011. Genome size estimates and chromosome numbers of Callicarpa L. (Lamiaceae). HortScience 46(4):567-570.
Contreras, R.N., J.M. Ruter, and B.M. Schwartz. 2010. Oryzalin-induced tetraploidy in Cryptomeria japonica (Cupressaceae). HortScience 45(2):316-319.
Contreras, R.N., J.M. Ruter, and W.W. Hanna. 2009. An oryzalin-induced autoallooctoploid of Hibiscus acetosella Welw. ex Hiern. ‘Panama Red’ (Malvaceae). J. Amer. Soc. Hort. Sci. 134(5):553-559.
Contreras, R.N. and J.M. Ruter. 2009. Sulfuric acid scarification of Callicarpa americana (Lamiaceae) seeds improves germination. Native Plants J. 10(3):283-286.
Contreras, R.N. and T.G. Ranney. 2008. New opportunities for breeding fragrant rhododendrons. J. Amer. Rhododendron Soc. 62(4):201-202.
Contreras, R.N., T.G. Ranney, and S.P. Tallury. Reproductive behavior of diploid and allotetraploid Rhododendron L. ‘Fragrant Affinity’. 2007. HortScience 42(1):31-34.