Influence of Alternaria spp. on susceptibility of canola and mustard to Pythium spp., Fusarium spp., and Rhizoctonia solani

Abstract

Seed exudates have been shown to inhibit the growth of some fungi responsible for seed rot and seedling blight in canola and mustard. Alternaria brassicae, A. alternata and A. raphani can all be found on seed of canola and mustard. Previous work indicates deep infections of Alternaria brassicae and A. raphani significantly reduce seed germination while A. alternata had no direct effect on germination. The objective of this study is to determine the effect of seed exudates on seed rot and seedling blight caused by Rhizoctonia solani, Fusarium spp. and Pythium spp. and determine if seed borne Alternaria is synergistic to these pathogens by breaking down defensive compounds in the seed exudates. Seed will be inoculated with Alternaria alternata. to create superficial surface infection. Susceptibility to Pythium, Fusarium and Rhizoctonia of artificially infected seed lots and naturally infected seed lots will be tested on water agar, blotter test and pot test. Seed exudates will also be obtained from seed lots after surface sterilization and bioassays of the ability of these exudates to support growth of pathogenic fungi and beneficial bacteria will be assessed.