INCREASING SEVERITY OF ATTACKS OF COLLETOTRICHUM COCCODES ON GRAFTED TOMATOES

A. Minuto, G. Gilardi, M.L. Gullino, A. Garibaldi
Since 1999 extensive monitoring has been carried out in order to identify the emerging soil-borne diseases affecting tomato in commercial fields where methyl bromide was progressively abandoned as required by national and international regulations. In 2003, tomatoes in Piedmont, Campania and Sicily were grafted on resistant rootstocks, and root rots were observed sporadically at the beginning and afterwards more frequently. On non-grafted tomatoes the symptoms were sometimes very similar to the root rots caused by Pyrenochaeta lycopersici, while on grafted tomatoes, grown together with non-grafted infected plants, symptoms appeared different. In non-grafted tomato plants, the root systems appeared extremely damaged, with large areas of necrosis completely deteriorating both older and younger roots. The root tissues became blackish, showing general cracks as in the case of corky root infections; however, contrary to corky root infections, the necrotic roots appeared with a cortex which was easily removed and the remaining internal root tissues assumed a blackish color. On the root system of rootstocks, the symptoms were particularly evident on older roots where the tissues were gray to blackish. On the basis of several analyses, a fungus producing blackish round sclerotia of a diameter less than 1 mm was always observed. Tests carried out to confirm Koch’s postulates confirmed the pathogenicity of the isolated fungi recognized as Colletotrichum coccodes, the causal agent of brown root rot of tomato. Tests carried out in pots with artificial soil infestation demonstrated the susceptibility to this disease of standard tomato plants and interspecific and intraspecific tomato rootstocks. These observations show that grafting tomatoes on resistant rootstocks cannot be considered the only practice to control soil-borne pathogens in C. coccodes infested soil.
Minuto, A., Gilardi, G., Gullino, M.L. and Garibaldi, A. (2008). INCREASING SEVERITY OF ATTACKS OF COLLETOTRICHUM COCCODES ON GRAFTED TOMATOES. Acta Hortic. 789, 101-106
DOI: 10.17660/ActaHortic.2008.789.12
https://doi.org/10.17660/ActaHortic.2008.789.12
Lycopersicon esculentum, black dot root rot, grafting, disease resistance
English

Acta Horticulturae