UK VEGETABLE SEEDS BROCHURE 2022-2023 - Flipbook - Page 64
Levels of
Resistance
Two levels of resistance are defined:
High/standard resistance (HR*)
Plant varieties that highly restrict the growth and development
of the specified pest or pathogen under normal pest or
pathogen pressure when compared to susceptible varieties.
These plant varieties may, however, exhibit some symptoms
or damage under heavy pest or pathogen pressure.
Moderate/intermediate resistance (IR*)
Plant varieties that restrict the growth and development of
the specified pest or pathogen, but may exhibit a greater
range of symptoms or damage compared to high/standard
resistant varieties. Moderately/intermediately resistant plant
varieties will still show less severe symptoms or damage
than susceptible plant varieties when grown under similar
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environmental conditions and/or pest or pathogen pressure.
Susceptibility is the inability of a plant variety to restrict the
growth and development of a specified pest or pathogen.
The Vegetable Section of ISF recommends, as it pertains
to biotic stress, that its members use the terms immunity,
high/standard or moderate/intermediate resistance
and susceptibility and to avoid the term tolerance in
communications with their customers.
Tolerance is the ability of a plant variety to endure abiotic
stress without serious consequences for growth, appearance
and yield. Vegetable companies will continue to use tolerance
for abiotic stress.