AmericanHort Recommends Terms for Disease Resistance Claims

Jennifer Zurko

AmericanHort and its research foundation, the Horticultural Research Institute (HRI), led an effort—at the request of industry representatives—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.

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.

AmericanHort and HRI said in a statement that they’re “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.”

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.”)

Jean-Marc Versolato, Production Manager, Plant Health Department, for Bailey Nurseries, said, “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 [about] 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.”

Shannon Carmody, Plant Pathologist, for Ball Horticultural Company, said, “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 on the HRI website at hriresearch.org. AmericanHort encourages all breeders and those involved in new plant introductions within environmental horticulture to follow this guidance. GT