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Resistant varieties

Resistant varieties consistently gave most effective control of foliage and tuber blight compared with diversification and agronomic strategies and alternative treatments to copper-based fungicides. They did not invariably outyield susceptible ones but decreased disease inoculum and consequently the risk of infection within and between crops. Applications of copper oxychloride to both resistant and susceptible varieties, improved blight control and yield in the most resistant varieties, improvements were relatively small. Growing resistant varieties is the most effective strategy to reduce or eliminate the need for copper-based fungicides in organic cropping systems whilst maintaining production. Reductions of between about 16.5 and 50% of current levels copper fungicide applications might be achieved by growing them instead of susceptible varieties to the maximum extent that the market could absorb. This potential advantage will only be realised if the resistant varieties that are or become available, are acceptable for the organic market and substitute for the susceptible but more popular varieties currently grown currently without decreasing economic returns. Shifts in regional/national late blight populations towards increased pathogenicity with more resistant cultivars in production seems unlikely but virulence to new R-genes bred into new cultivars cannot be ruled out completely.

Informations connexes

Reported by

Swiss Research Institute of Organic Agriculture (FiBL)
5070 FRICK
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