"He couldn't sequence the wheat's DNA to figure out which genes caused which traits, because that technology was decades away.
But he could cross the varieties which had some good traits, and hope that one of the cross-breeds would happen to have all the good traits and none of the bad.
It was painstaking work, but eventually it paid off.
Borlaug produced new kinds of "dwarf" wheat that resisted rust, yielded well, and - crucially - had short stems, so they didn't topple over in the wind."
But he could cross the varieties which had some good traits, and hope that one of the cross-breeds would happen to have all the good traits and none of the bad.
It was painstaking work, but eventually it paid off.
Borlaug produced new kinds of "dwarf" wheat that resisted rust, yielded well, and - crucially - had short stems, so they didn't topple over in the wind."