BROWN ROOT ROT OF TOMATOES I. THE ASSOCIATED FUNGAL FLORA

Tomato roots with brown root rot showed three types of lesion: cortical rot of fine roots, 'corky root', and basal stem rot. The fungi most commonly isolated from diseased roots were : Colletotrichum atramentarium, Chaetomium spp., Cephalosporium spp., Volutella ciliata, and a grey mycelial fungus sometimes producing pycnidia (Pyrenochaeta sp.). Other fungi isolated less frequently were: Myrothecium roridum, Petriella asymmetrica, Trichoderma viride, Phytophthora spp., Alternaria sp. and Fusarium spp. There were differences between the numbers of each species isolated from the three types of lesion in steamed and in unsteamed soils, and some seasonal variation. Inoculation experiments with seedlings in vitro showed that Ckaetomium cochliodes and Petriella asymmetrica could infect radicles. On older plants growing in soil Colletotrichum atramentarium was the only effective pathogen. Culture filtrates from C. atramentarium, Chaetomium cochliodes, and P. asymmetrica decreased root growth when tested in vitro. Leachates from loam and a loam-manure mixture decreased the growth of tomato root-tip cultures; the effect of these leachates was altered by autoclaving.