MEASUREMENT OF FIELD-RESISTANCE OF POTATOES TO VERTICILLIUM WILT (VERTICILLIUM-DAHLIAE)

Twenty seven clones were trialled in the Negev, Israel, in both the Spring and Autumn planting seasons of 1984 and 1985 and of these clones 18 were also grown in the Spring of 1986. All clones were grown in fumigated soil (designated, Control) which was subsequently kept as disease-free as possible and in soil previously infested with Verticillium dahliae, the causal agent of Verticillium wilt and a component of the potato early-dying syndrome. The clones differed in maturity and showed a range of symptoms in the field. A true assessment of resistance or susceptibility could not be obtained unless allowance was made for the effects of maturity. Only a few clones showed significant resistance. The importance of the results, in relation to screening breeders' clones for resistance, is discussed.