I had heard that modern wheat variants were heavily dependent on agrochemicals (pesticides and fertilisers) but apparently that was wrong: Modern wheat outperforms older varieties even if less fertiliser, water or pesticide is used.
It is simply more robust.
That conclusion is actually a by-product of a study that tried to pinpoint how modern wheat varieties could be bred to yield even more. The study claims a theoretical 23% gain is possible.
You can find the article regarding the study using DOI: 10.1038/s41477-019-0445-5, if you know how.
Henning's blog 