 Fifteen years later in the early 1960s there was a severe epidemic of stripe rust, and hundreds of seed collections were tested for resistance to the rust.PI 178383 turned out to be resistant, not only to the stripe rust, but to several other wheat diseases as well, and it was added to breeding programs to produce new, resistant varieties, which were widely grown in America's northwestern states.Harlan agreed broadly with Vavilov's idea that just a few geographical locations are crucial for generating much of the biodiversity on which plant breeders depend.