Rhizopus and Fusarium are selected as dominant fungal genera in rhizospheres of Brassicaceae

We isolated several strains of Rhizopus and Fusarium spp. as dominant fungi in the rhizospheres of Brassicaceae plants. The Fusarium isolates showed a higher tolerance of the antifungal constituents of "mustard oil," which or iginates from the glucosinolates that are characteristic secondary metaboli tes of the Brassicaceae, than other Fusarium isolates from non-Brassicaceae plants. In contrast, the Rhizopus isolates showed a high tolerance regardl ess of their source. Myrosinase activity was found in Bn-R-1-1 (Rhizopus sp .) isolated from the rhizoplane of Brassica napus and Ls-F-in-4-1 (Fusarium sp.) isolated from a surface-disinfected root of Lepidium sativum (Brassic aceae). Ls-F-in-4-1 was the Fusarium most tolerant of the Brassicaceae anti fungal constituents. These results suggest that fungi in the rhizospheres o f Brassicaceae plants may be selected because of secondary metabolites exud ed from the roots of host plants.