Occurrence of a resistance breaking pathotype of Meloidogyne javanica on tomatoes in Crete, Greece.

The root galling and reproduction of five single egg mass lines of Meloidogyne javanica originating from three different field sites of Crete was assessed on fourteen resistant tomato hybrid cultivars (Scala, 7352 Silco, Myrto, Menglo, Rakata, GC785, GC788 Alpado, Bermuda, 7353, 7358, W1964, W1967, W2913, 399) in a controlled environment where soil temperature was 22-24 degree C. Two lines originating from a field where the resistant cv. Menglo had been grown for two years were able to infect the resistant cultivars and to reproduce on them as well as on a susceptible cultivar (Carouso). One line isolated from cucumber infected and reproduced only on the susceptible cultivars. Two lines from a field where the susceptible cultivar Carouso was grown showed either slight or no reproduction on resistant cultivars. Under greenhouse conditions (soil temperature 20-42 degree C) Mi conferred resistance was nullified and all cultivars became hosts for an avirulent line.