A NEW AGGRESSIVE STRAIN OF VERTICILLIUM ALBO-ATRUM IN VERTICILLIUM RESISTANT CULTIVARS OF TOMATO IN THE NETHERLANDS

In 1991 serious losses caused by Verticillium wilt were found on two h oldings in the Westland glasshouse district in the Netherlands in whic h the Verticillium resistant tomato cultivars Calypso and Criterium we re grown in soilless systems. Isolates from diseased plants were ident ified as Verticillium albo-atrum. In inoculation experiments Verticill ium resistant tomato cultivars were seriously affected by the new isol ates but not by a control isolate. Moneydor, a susceptible cultivar wi thout the Ve gene, was the most seriously diseased by all isolates. Th e isolates from the Verticillium resistant tomato cultivars were less virulent on the susceptible cultivar than the control isolate.