But you can slow down that process by crop rotation, for example in canola there are many known resistance genes for blackleg (fungus) infections. Farmers are i

But you can slow down that process by crop rotation, for example in canola there are many known resistance genes for blackleg (fungus) infections. Farmers are in many places advised to rotate their canolas to different resistance genes so the fungus cannot build up resistance so quickly See for example https://grdc.com.au/resources-and-publications/groundcover/ground-cover-supplements/ground-cover-issue-116-foliar-fungal-diseases-of-pulses-and-oilseeds/rotate-resistant-varieties-to-outflank-blackleg https://grdc.com.au/resources-and-publications/groundcover/g... I cannot find any data where that particular fungus has gained and then subsequently lost its resistance to a plant resistance gene, but it wouldn't be impossible as long as the particular plant variety is not sown