IN-PLANTA IMMUNOLABELING OF 3 TYPES OF PERIPHERAL VESICLES IN CELLS OF PHYTOPHTHORA-CINNAMOMI INFECTING CHESTNUT ROOTS

Micropropagated plantlets of an improved selection of chestnut (Castan ea saliva) that was susceptible to Phyliophthora root rot, were inocul ated in vitro at the root tip with zoospores of Phytophthora cinnamomi . Plantlets were then incubated for up to 4 d, during which time infec tion was examined by clearing and staining whole roots or immunolabell ing cryosections with monoclonal antibodies specific for fungal vesicu lar components. Hyphae had colonized entire root systems by 3 d after inoculation and plantlets were dead by 4 d after inoculation. Three ty pes of fungal vesicles, large peripheral, dorsal and ventral vesicles, were immunofluorescently labelled in hyphae infecting roots from 1 d after inoculation with zoospores. Their appearance correlated spatiall y and temporally with the production of sporangia and chlamydospores. Vesicles were not observed in fungal cells at the advancing hyphal fro nt, but appeared similar to 5 mm behind the growing front. Large perip heral vesicles were also immunolabelled in oospores formed after 10 wk in roots of plantlets inoculated with A1 and A2 mating type isolates of P. cinnamomi, either together or alone.