When the Plants Start Talking to You: Breeding New Ornamentals Gamma rays, seedless shrubs, and the unglamorous skill that still beats every fancy technique. Episode Description There is a cobalt source on the Oregon State campus, and Dr. Ryan Contreras uses it on plants. He describes the method with a shrug and a movie line: “The Forrest Gump, life is like a box of chocolates. We never know what we’re going to get. We’re just taking a shotgun and pointing it and blasting and then growing out populations of those looking for useful variation.” That is mutagenesis, one tool among many in a program that keeps germplasm or small projects on close to 50 genera. Ping asked Ryan for the whole toolkit, and he gives it: sexual recombination as the workhorse, crossing elite by elite to move fire blight resistance into a plant the industry already likes, ploidy manipulation to make seedless forms the way a triploid banana is seedless, chemical and radiation mutagenesis, targeted gene editing, and the tissue culture step that woody plants keep refusing to cooperate with. He explains why ornamental breeders rarely backcross, since woody plants suffer from inbreeding depression and many will not self-pollinate at all. Then he shows where the ideas actually come from: a Kolkwitzia he taught for years because it was climbing over a seven-foot privacy fence onto the sidewalk, a Philadelphus madrensis whose fragrance reached him from a hundred feet away at the Santa Cruz Arboretum, and growers in Oregon asking him to fix cherry laurel. Underneath the techniques runs an argument that will not go out of style, because it never went in. The technique Ryan relies on most is walking the plots and looking at plants, and he has thirteen years of lilac sequencing without a validated marker to show for the alternative. He is unusually candid about the misses too: a triploid Cotoneaster with pink flowers, good fall color, and total fire blight resistance that nobody wanted because it had no berries, and a flat admission that some of what he releases over a career will be duds. Growers, students, and anyone who has wondered how a new shrub gets to a garden center will find something to take home. Listen Time: 52:52 Follow Along with the Transcript In This Episode Guests Dr. Ryan Contreras, Professor, Department of Horticulture, Oregon State University. Ornamental and woody plant breeder, at OSU since December 2009. He earned his PhD with Dr. John Ruter at UGA (Tifton), his master’s with Dr. Tom Ranney at NC State, and his first taste of plant breeding as an undergraduate working with Denny Werner on Buddleja. Dr. Ping Yu, host, UGA Department of Horticulture. Main Topics Welcome and meet Dr. Ryan Contreras (0:00) Mentors, and the technicians who get left off the thank-you list (4:52) Chicken houses, ag ed, and the class that changed everything (7:06) The summer that ended the nursery dream (9:29) What plant breeding actually is (12:38) Ploidy, mutagenesis, and the cobalt source (15:50) Why ornamental breeders rarely backcross (18:27) Where breeding ideas come from (21:53) Grower problems: cherry laurel and maples (23:54) Trends, pain points, and brands (25:12) Borlaug’s advice: walk the plots (29:10) The watering analogy, and having an eye (32:28) Lilacs, where markers have not caught up (34:10) Reblooming, remontancy, and validation (35:43) When a grower changes your breeding goal (38:48) Time, money, and what gets bred (42:37) The Cotoneaster nobody wanted (45:21) Training the next generation of breeders (48:25) Where to follow the Contreras lab (50:16) Key Highlights The toolkit, plainly explained. Ryan starts from the idea that breeding is not a complicated science: create variation, then choose. Everything else is method. He walks through recombination, elite by elite crossing, ploidy manipulation for seedless forms, EMS and gamma mutagenesis, transgenics, and targeted editing, and he is honest about where woody plants stall. Corn, cotton, soy, and wheat have chromosome-level genome assemblies and known gene targets. Nursery crops mostly do not, and regeneration from undifferentiated callus is the bottleneck. Ideas arrive by accident as often as by plan. The Philadelphus breeding program at OSU exists because a fragrance carried a hundred feet across the Santa Cruz Arboretum and Ryan went to find its source. The Kolkwitzia project exists because the only teaching specimen he could reach was hanging over a fence, bulletproof and far too big. A grower said no, and the program changed. Ryan brought polyploid arborvitae that would not brown in winter to A&R Spada Farms and heard “I don’t care about that.” Customers call about winter browning, the nursery tells them to wait two months, the plants green up, and the calls stop. What the grower wanted instead was spruce spider mite resistance, which costs real money every season. Who the plants are for. His triploid Cotoneaster survived 4 degrees Fahrenheit unprotected in a container, resists fire blight, roots well, and has pink flowers and good fall color. It has no berries, so the market passed. He kept a few plants and took the lesson. Advice for students. Learn how the plants are grown before anything else. In his program nobody leaves without doing flow cytometry, looking at pollen under a microscope, sticking cuttings, and processing seed. His closing plug is for IPPS, where students meet growers and see operations. Key Quotes “You go to the field, and you go to the field some more, and when the wheat plants start to talk to you, you’ve made it.” Norman Borlaug, quoted by Ryan Contreras (29:36) “I would say, I think of it like at a lot of nurseries, the lowest paid person is the most important person, it’s the watering.” Ryan Contreras (32:55) “I’m not breeding plants for what I think I want. I’m breeding plants for what people who are in the industry, what they need and what they want.” Ryan Contreras (46:40) “There’s no shortage of nearly unattainable goals. We want a plant to get three feet in one year and then not grow anymore, require no fertilizer and flower 52 weeks a year.” Ryan Contreras (41:48) “So everything is gonna come back around and it takes me 17 years to release a cultivar.” Ryan Contreras (28:55) Educational Highlights Creating variation, then choosing. Ryan’s working definition of plant breeding: observe variation and select something better for the trait you care about. Sexual recombination, through a deliberate cross or collected seed, remains the most common and easiest way to get that variation. Elite by elite. Crossing two good parents does not mean two perfect parents. In Cotoneaster, Ryan takes a plant that grows well in production and has the shape the industry wants but lacks fire blight resistance, and crosses it with a resistant plant to bring the two together. Ploidy manipulation. Doubling or changing the number of chromosome sets. In Ryan’s program the most common reason is seedlessness: bananas are triploid, and triploidy renders them seedless. The same trick applied to nursery crops removes unwanted fruit and volunteer seedlings. Mutagenesis, targeted and not. Non-targeted mutagenesis uses chemicals such as ethyl methanesulfonate (EMS) or physical mutagens such as x-rays and gamma rays. OSU’s radiation center has fast neutrons and a cobalt source that gives off gamma radiation. Targeted editing is the newer path and depends on knowing which gene to aim at. The regeneration bottleneck. Gene editing and transgenics usually require regenerating a whole plant from undifferentiated callus tissue. Most woody ornamentals will not do it. New work on introducing CRISPR through non-tissue-culture-based methods would remove that step, which Ryan calls another huge leap forward. Backcrossing and inbreeding depression. A backcross means crossing a hybrid offspring back to one of its parents, as Ping defines it in the episode. Woody ornamentals are highly heterozygous and tend to suffer from inbreeding depression, and many will not self-pollinate. Hibiscus syriacus cultivars mostly self at very low rates, and the few seeds you get are weaker. Ryan’s workaround is what he calls a pseudo-backcross: existing Hibiscus syriacus by Hibiscus paramutabilis hybrids crossed back to H. syriacus for cold hardiness, improving on Tosca, Lohengrin, and Resi. Remontancy and reblooming. Repeat flowering reset customer expectations for whole genera: Encore azaleas, Endless Summer hydrangeas, Knock Out roses. Environment can fake it. ‘Palibin’ lilac has no reblooming genes, but shear it in early spring and it will flower in July, which Ryan saw in full bloom at Van Essen Nursery in late July. Telling a gene from a management effect is why field observations get validated with markers. Markers and QTLs, in perspective. Marker-assisted breeding has clear wins: nematode resistance in peanut, and the hazelnut program next door to Ryan that broke eastern filbert blight. His lilac work has been running since 2013 without a validated, effective marker, which is why he keeps asking whether a technique is getting him closer to a cultivar. Pest and disease terms from the episode. Shot hole disease and seediness in cherry laurel (Laurocerasus), western cherry fruit fly and the shipping restrictions it creates for Oregon growers, fire blight in Cotoneaster, spruce spider mite in arborvitae, and rhodoxanthin, the pigment behind that brown or purple cast on ‘Smaragd’ arborvitae in winter. Resources & Links Website: bandbpod.com The Contreras lab: horticulture.oregonstate.edu, under People IPPS, the International Plant Propagators’ Society, which Ryan recommends to students for meeting growers and seeing operations. Its motto, “to seek and share,” comes up in his sign-off ASHS and ISHS, both mentioned alongside IPPS as the societies students usually join first Oregon State University D
