What is the difference between ‘classical’ and ‘non-classical’ pathogen resistance genes in plants?

Question

I have stumbled across a mention of classical resistance genes against pests in plants, however the classification seems a bit vague.

What would be classified as classical resistance genes and what as non-classical in plants?

Edit:

Found it here:

'For example, the identification of classical plant resistant genes in Arabidopsis and other model dicots facilitated the successful cloning of multiple wheat rust resistant genes (Ellis et al., 2014; Wulff and Moscou, 2014).'

• Schwessinger, Benjamin, et al. "Focus issue on plant immunity: from model systems to crop species." Frontiers in plant science 6 (2015): 195.

Answer 1

I edited to reflect that the reference is to classic genes rather than to classic immunity.

Note that this is not a formal definition but rather an informal way of talking about the state of the scientific literature: "classic" or "classical" is a way of referring to the first-described, standard, or most familiar example of a phenomenon.

The term "classic" has no biological salience, but rather has salience for the history of science and what is in textbooks (e.g. the necessarily subjective human perception of nature).

See e.g. this blog post discussing this loose way of writing.