Aspects of the biology of chlamydospores of Phytophthora cinnamomi.  F. Y. Kassaby.  February 1979.  25 pp. (unpubl.)

SUMMARY

One of the asexual propagules of the soil fungus Phytophthora cinnamomi is the chlamydospore. These spores are thought to be important for the long term survival of the fungus, particularly when environmental conditions do not favour immediate infection of host material. It is important to discover the mechanisms of chlamydospore formation and germination and the role these spores play in the disease cycle for possible future disease control.

This study reviewed the literature on the types of propagules of P. cinnamomi in soil and the process and physiology of chlamydospore germination. The formation, morphology and behaviour of chlamydospores of a Victorian isolate were described and discussed.

The literature showed that germinating chlamydospores produced either one or more germ tubes, a germ tube bearing a sporangium or as observed by the author, gave rise directly to zoospores.

This study observed the formation of hitherto undescribed endogenous non-motile spores (micro-endo-chlamydospores) within chlamydospores, mycelium and hyphal swellings. The micro-endo-chlamydospores were induced to germinate producing hyphae or sporangia.

The significance of micro-endo-chlamydospores has not been determined but it is suggested that they may:

1. provide an additional effective means of survival,
2. intensify the disease producing capacity of the fungus (more propagules) and,
3. assist the fungus in dispersal.