Durable Vertical Resistance

It was mentioned earlier that there are a few examples of vertical resistance that has proved durable. These examples include:

Wart disease (Synchytrium endobioticum) of potato in Western Europe has endured unmatched for many decades. The vertical resistance is supported by strict legislation that precludes the cultivation of susceptible cultivars in wart-contaminated fields.

Stem rust (Puccinia graminis tritici) of spring wheats in Canada. The combination of vertical resistance genes Sr6 and Sr9d has proved durable. The matching race is common in Mexico and regularly spreads northwards each summer but it apparently arrives in Canada too late to cause any damage. This pathogen cannot survive the Canadian winter. It should also be remembered that most Canadian wheat cultivars are early-maturing and are harvested before damaging epidemics can develop.

Fusarium wilt (Fusarium oxysporum f.sp. lycopersici) of tomato in North America. This vertical resistance has proved durable in the United States but it fails quickly in other areas, such as North Africa.

Cabbage Yellows (Fusarium oxysporum f.sp. conglutinans) has a vertical resistance that has proved durable in North America.

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