SUSCEPTIBILITY OF SOME TOMATO CULTIVARS TO BACTERIAL CANKER AND SPOT DISEASES AND THE ROLE OF SEEDS IN PATHOGEN TRANSMISSION*

Abstract

Bacterial canker caused by Clavibacter michiganensis subsp. michiganensis (Smith) and bacterial spot caused by Xanthomonas campestris pv. vesicatoria (Doidge) Dye have become important diseases of tomato in Egypt. The present work was planned to evaluate the reaction of different tomato cultivars and the role of seeds to transmit both pathogens. Cultivars of Dora, Flora-Dade, KTM141, Money Maker, Niagra, Super strain B hybrid and GS12 were moderately resistant to both diseases, but Castle rock, Peto 86 and Super strain B cultivars were susceptible. However, Castle rock, Peto 86, Super strain B and Niagra cultivars were highly susceptible for bacterial canker than spot disease. Using the Liquid assay method, C. michiganensis subsp. michiganensis bacterium could be detected in seeds of cultivars Dora, KTM141, Niagra and Super strain B hybrid, but X. campestris pv. vesicatoria was detected on seeds of cultivars GS12, Peto 86 and Super Marmand. However, both bacterial pathogens were not detected in seeds of all cultivars, except GS12, when direct planting method on selective media was used. In an in vivo assay, bacterial canker has developed more than bacterial spot disease on tomato seedlings produced from non-treated seeds. Bacterial canker has developed on all tested cultivars at different frequencies. Transmission of both pathogens occurred at high frequency by seeds of cultivars Niagra and Dora, however bacterial spot was not borne on samples of other tomato cultivars