PRODUCTION OF PHYTOTOXIC SPORE GERMINATION LIQUIDS BY ALTERNARIA BRASSICAE AND A-BRASSICICOLA AND THEIR EFFECT ON SPECIES OF THE FAMILY BRASSICACEAE

Experiments assessed the susceptibility of Brassica spp. and non-Brass ica spp. in the family Brassicaceae to infection by Alternaria brassic ae and A. brassicicola, and determined the sensitivity of the host spe cies to spore germination Liquids (SGLs) produced by the pathogens on B. napus leaves. There was a wide range of sensitivity to the pathogen s. Brassica spp, were generally more susceptible, and some non-Brassic a spp. (Barbarea vulgaris and Capsella bursa-pastoris) were immune to A. brassicicola. Measurable damage was caused by SGLs but with signifi cant variation between host species. Non-hosts and weak hosts also sho wed necrosis. It was concluded that, in the case of both pathogens, th e toxic factors in these SGLs were host-selective. Selectivity in toxi n production was also demonstrated in relation to the host surface or growing medium in which spores germinated. A substantial amount of tox in was produced on all Brassicaceae tested but not on unrelated specie s (Triticum aestivum, Pisum sativum and Lycopersicon esculentum). Neit her pathogen produced measurable amounts of toxin when cultured in Cza pek (Dox) broth.