Chlamydospore formation in hyphae of Fusarium oxysporum f. sp. raphani.

Chlamydospore formation in hyphae of Fusarium oxysporum f. sp. raphani was studied as a function of time. Hyphal suspensions were aseptically incubated in a salt solution supplemented with 0.01% glucose at 26-28° and examined by light microscopy. We counted both typical chlamydospores and chlamydospore-like bodies (CL bodies) in hyphae across the 0.3mm diameter of a microscope field. When arranged in a frequency distribution, the experimental data suggest that typical chlamydospores and CL bodies were formed in hyphae by chance. The formation of both bodies was characterized as a first order reaction. The number of CL bodies exceeded those of typical chlamydospores in all experiments. The optimal pH for the formation of both bodies was between 6.5 and 7.0. Autolysis of hyphae was observed after 8 or 9 days incubation. Apparently CL bodies are not precursors of chlamydospores. We recognize three distinct stages in the behavior of hyphae in carbon deficient media: 1. Hyphae continue to grow and chlamydospores and CL bodies are not formed in the first 3 days of incubation. 2. Chlamydospores and CL bodies are formed at constant rates but hyphae do not grow appreciably. 3. Hyphae begin to autolyse and coincidently the formation of chlamydospores and CL bodies ceases. Chlamydospore formation is considered to occur in a limited period under starved condition.