Resistance Statement


Infectious plant diseases are caused by pathogenic organisms with amongst others fungi and viruses. Worldwide they can cause severe crop losses but also reduce the aesthetic values of landscape plants and home gardens even though chemical control measures are often applied. The goal of the Dümmen Orange breeding teams is to develop varieties being resistant to important diseases that require fewer chemical applications and that are more sustainable for both producers and customers.

Often the terms resistance and tolerance are used interchangeably, and oftentimes resistance is mistakenly thought to equal immunity. Industry representatives requested an AmericanHort - led 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.


AmericanHort recommends the environmental horticulture industry use the terms immunity, susceptibility, and high or intermediate resistance to describe the reaction of a plant to pathogens, whereas the term tolerance should be used to describe abiotic stresses in marketing communications with customers. The definitions provided below are meant to provide clarity for claims made of newly released plant material relative to a particular disease(s) or abiotic stress(es) at the time of testing. Changes in resistance are not covered under the original claim.

Immunity is when a plant cannot be infected by a given pathogen.

Resistance is the ability to exclude, hinder, or overcome the effects of a specified pathogen; the opposite of susceptibility. Resistant varieties may exhibit some disease symptoms or damage under heavy pathogen pressure and/or highly conducive environmental conditions. Two levels of resistance are defined: high and intermediate.

  • High Resistance describes plant varieties that can be infected but restrict the growth and/or development of the specified pathogen and/or the damage it causes.
  • Intermediate Resistance describes plant varieties that restrict the growth and/or development of the specified pathogen and/or the damage it causes but may exhibit a greater range of symptoms or damage compared to highly resistant varieties. Plant varieties with intermediate resistance will show less severe symptoms or damage than susceptible plant varieties when grown under similar environmental conditions and/or disease pressure.

It is to be noted that if resistance is claimed in a plant variety it is limited to the specified biotypes, pathotypes, races or strains of the pathogen that it has been tested against.

Susceptibility is the inability of a plant to resist or restrict the invasion of a pathogen; the opposite of resistance.

Tolerance is the ability of a plant variety to endure abiotic stresses without serious consequences for growth, appearance, and yield.

Q&A on Dümmen Orange on Intrinsa®

Q: What is Intrinsa®? When does a variety get the label Intrinsa®?
A: Intrinsa® is the label at certain Dümmen Orange varieties to explain it brings advanced hybridization techniques through traditional breeding to create sustainable and economically viable plants for a greener future. For instance varieties that are resistant to major diseases.

Q: Can other breeders use Intrinsa® varieties in their breeding program?
A: Use of patent protected Intrinsa® plant material will be subject to prior approval of Dümmen Orange in those markets, but we are open to discuss license arrangements, which would enable other breeders to use our innovations.

Q: Will the Intrinsa® resistance be introduced globally?
A: Yes.

Q: Is it important to know how many resistance genes are in our resistant varieties?
A: No. But please feel free to contact your account manager for more information.


We claim the resistance as specified on the specific crop pages. Pathogens may evolve and can overcome resistance. Therefore, any resistance claim made reflects the status of a plant at the time of testing. Changes in resistance over time may not be covered under the original claim.

For more information, please contact Dümmen Orange at