AmericanHort & HRI Recommend Terms for Disease Resistance Claims

HRI Research • August 20, 2020

AmericanHort and its research foundation, the Horticultural Research Institute (HRI), are dedicated to unifying the environmental horticulture industry to cultivate successful businesses and help enhance lives through the benefits of plants. AmericanHort prides itself in listening to industry needs and relies on stakeholder input to drive its focus and efforts, including the recent industry-initiated movement to standardize the terms used as marketing tags on newly released plant material in reference to specific diseases and/or abiotic stresses.

Disease resistance and tolerance to abiotic stresses (such as drought, cold exposure, others) in plants contribute greatly to plant health and ultimately to the success of our industry. As more new plants are anticipated to be released targeting disease and/or abiotic stress management, the industry will be faced with how to best represent these traits to customers and set performance expectations. Often the terms resistance and tolerance are used interchangeably, and oftentimes resistance is mistakenly thought to equal immunity.

At the request of Industry representatives, AmericanHort led an effort to explore an industry-wide adoption of specific terms to be used in the event of a new plant release when describing disease resistance and/or tolerance to abiotic stresses to help avoid unsubstantiated and misleading claims.

Jean-Marc Versolato, Production Manager, Plant Health Department, Bailey Nurseries, participated in the process and commented, “It’s a good idea for the whole industry to use the same words to describe a plant’s response to stress and to clarify the specific pathogen or agent tested. This is useful so that the end customer understands the claim being made, and there is no ambiguity a plant’s resistance or tolerance to a stress. It becomes a truer statement and no longer misleads the customer into thinking a plant is resistant to all sorts of problems.”

A working group made up of the research community and industry breeders advised a set of clear definitions for the terms immunity, high or intermediate resistance, susceptibility, and tolerance to be used industry-wide going forward. Disease specifics should be included on marketing claims. For example, a tag on an impatiens plant should state ‘High Resistance to Impatiens Downy Mildew’ as opposed to ‘High Resistance to Disease.’

Shannon Carmody, Plant Pathologist, Ball Horticultural Company, commented on the process, “The development of downy mildew resistant Impatiens started a conversation internally at Ball Horticultural Company about how to use accurately disease resistance language in breeding, product development, and marketing for ornamental crops. We look forward to working with other industry stakeholders to improve clarity and consistency for our customers.”

The full white paper is available here . AmericanHort encourages all breeders and those involved in new plant introductions within environmental horticulture to follow this guidance.

###

Green industry businesses perform better, grow faster, and prepare for the future as a member of AmericanHort, the green industry’s leading association. With a rich history of serving horticultural professionals, AmericanHort supports nearly 15,000 members and affiliated businesses that include breeders, greenhouse and nursery growers, garden retailers, distributors, interior and exterior landscape professionals, florists, students, educators, researchers, manufacturers, and all of those who are part of the industry market chain. The horticulture industry's production, wholesale, retail, and landscape service components have annual sales of $346 billion, and sustain over 2.3 million full- and part-time jobs. AmericanHort works to impact the growth, performance, and successful future for the industry through advocacy, research, education, and advancing industry standards. Visit www.americanhort.org for news and information.

The Horticultural Research Institute (HRI), the research affiliate of AmericanHort, has provided over $9 million in funds since 1962 to research projects covering a broad range of production, environmental, and business issues important to the green industry. Over $14 million is committed to the endowment by individuals, corporations, and associations. For more information about HRI, its grant-funded research, scholarships, or programming, visit www.hriresearch.org or contact Jennifer Gray at 614.884.1155.

< Older Post

Newer Post >

Share This Post

Soilless Substrate Science - Ushering in the Next Generation of Growing Media

By Jennifer Gray • May 28, 2026

Soilless Substrate Science (S3) is a national transdisciplinary collaboration developed to support growers as we advance to the next generation of substrates. Our team is leading North American efforts to develop new substrate materials and techniques, and working with growers to support implementation, as we support the global transition to substrates that go Beyond Peat. In this webinar, Dr. Jeb Fields will discuss the S3 team efforts surrounding identification of new substrate materials, processing and development, and grower support. We will explore wood fiber processing, sugarcane bagasse substrate development, stabilization of organic fibers, databasing substrate materials, and opportunities for growers to get involved. Overall, attendees will learn about US efforts to develop domestically-sourced substrates and advance substrate science as we move towards the next generation of substrate science. Our Speaker Dr. Jeb Fields is a production horticulturist who works with growers in Florida and throughout the country to support more effective and efficient production practices through his environmental nursery research program. Jeb’s primary interests include growing media & substrate science, irrigation & fertilizer management, whole plant-water relations and plant abiotic stress physiology. Jeb is an internationally recognized substrate scientist, the leader of the Beyond Peat project through the USDA Specialty Crops Research Initiative, and the national S3 (Soilless Substrate Science) team which pursues advancements of the global substrate industry and development sustainable substrate materials and practices, including substrate stratification. Jeb is the editor for Nursery & Landscape Insider, a biweekly e-newsletter from Ball Publishing, that reaches over 32,000 stakeholders worldwide. For his efforts, he has been recognized with numerous awards, honors, and leadership positions. Prior to joining UF, Jeb was a professor and research station director with the LSU AgCenter. Jeb studied at UF for his B.S., NC State University for his M.S., and Virginia Tech for his Ph.D. – with all degrees focusing on production horticulture.

A soft-focus background of varying shades of green, suggesting grass, foliage, or a forest landscape.

Understanding Why Rose Rosetting Disease Appears in Distinct Regions of a Shrub Rose Plan

By Jennifer Gray • April 9, 2026

This webinar dives into the problem of rose rosette virus. Shrub roses consist of multiple canes attached to a root system and produce beautiful spring growth in the form of new flowering stems and branches. Experts will provide an overview of how rose rosette virus first attacks flowering growth and can move throughout the stem. At the same time rosette symptoms appear in mature distinct stems of a plant and may be absent from others. The research delves into understanding how the vascular system connects the flowering stems and above ground canes. The research is to understand how virus movement between adjacent stems and only appears to cause disease in a few but not all canes of the same plant. This research is important to explore potential management approaches to safeguard rose.

From Propagation to Consumers: HRI Research Powers Every Link in the Green Industry Supply Chain

By Jennifer Gray • March 24, 2026

The horticulture industry continues to change as new technologies, production practices, and consumer expectations reshape the marketplace. Research plays an essential role in helping growers, landscapers, and retailers adapt and succeed. That’s exactly where the Horticultural Research Institute (HRI) enters the chat. Every year, HRI selects and funds research projects that advance horticulture. In 2026, HRI is investing more than $560,000 in 18 research projects that target challenges across the horticultural supply chain, including plant production, pest and disease management, landscape plant performance, and consumer insights. “What makes HRI research so valuable is that it focuses on real challenges the industry is facing right now,” said Mark Yelanich, HRI President and Research Director at Metrolina Greenhouses. “The 2026 HRI-funded projects were selected because they develop knowledge, processes, or tools that businesses can actually use.” HRI’s four strategic research priorities guide funding decisions, focusing on quantifying plant benefits, creating innovative solutions, gathering consumer insights, and producing practical solutions to industry challenges. The 2026 projects reflect these priorities across the horticulture supply chain.