Temporary resistance

First, as is now abundantly obvious, vertical resistance is temporary resistance when it is employed on a basis of host population uniformity. It fails to operate on the appearance of a matching strain of the parasite. And, because vertical resistance has been used whenever it could be found, this disadvantage has tormented most of twentieth century crop science. A few vertical resistances have proved to be durable and are discussed below (see 5.7). However, they do not invalidate the general rule that vertical resistance is ephemeral when employed on a basis of crop uniformity.

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