The mycorrhizal endophytes ofGriselinia littoralis(Cornaceae)

Abstract

The normal endophyte of Griselinia littoralis is an obligate symbiont identified as Rhizophagus populinus Dangeard. Its morphology and behaviour, when attempts are made to establish agar cultures from root pieces, are similar to those reported by investigators in several countries studying a wide range of hosts. A fungus with similar arbuscles but smaller vesicles and narrower hyphae may occur independently, or with R. populinus. Like R. populinus it stimulates growth in poor soils. It is named R. tenuis sp. nov. When pieces of root were placed on soil agar, hyphae of R. populinus emerged from 70–90% of them, and grew for 2–3 weeks in association with moulds and bacteria. It was impossible to ascertain whether the finer mycelium of R. tenuis behaved similarly. The growth of R. populinus was greatly reduced when all other organisms were killed by surface sterilisation of root sections, and did not respond to nutrients in the agar, or to the presence of autoclaved hemp seed. Attempts to synthesise mycotrhizas using cultures of Pythium or a culture of Rhizophagus from Dr J. T. Barrett did not succeed. A search for Endogonaceous fructifications associated with the roots of G. littoralis was unsuccessful.