Chitinase-gold complex used to localize chitin ultrastructurally in tomato root cells infected by Fusarium oxysporum f. sp. radicis-lycopersici, compared with a chitin specific gold-conjugated lectin.

A cytochemical technique for the ultrastructural localization of chitin in tomato root cells infected by Fusarium oxysporum f. sp. radicis-lycopersici is reported. Chitinase was complexed to colloidal gold and thin sections were incubated with the enzyme-gold complex. This technique yielded a more uniform distribution of gold particles over the fungus wall, compared to that obtained with the lectin-gold technique. Both techniques revealed no labelling of the fungus cytoplasm, except for organelles resembling Woronin bodies. No significant labelling of either healthy or infected root cells was seen except for the secondary walls of vessels and, occasionally, that of adjoining parenchyma cells. The importance of this technique in studying the development of the pathogen within host cells is discussed.