Fungi Associated with the Roots of Red Mangrove, Rhizophora Mangle

SUMMARY

The microbial communities of root-free soil, the rhizosphere and rhizoplane of red mangrove seedlings, Rhizophora mangle L., growing in Heeia swamp, Oahu, Hawaii, were studied by dilution plating, Harley and Waid's repeated washing technique, and a root maceration method. In addition, macrofungi associated with R. mangle roots were observed directly. By this combination of methods eight new records for fungi associated with mangroves were established. The isolation methods selected for isolating root-associated fungi are discussed. Results are evaluated within the limits of the methods employed.

There was a pronounced rhizosphere effect with greater numbers of bacteria, actinomycetes, and fungi occurring at all salinity levels in the rhizosphere soil than in the root-free soil at corresponding salinity levels. Primarily the microfungi isolated from the rhizoplane were known root-surface or root-tissue fungi. In the rhizosphere community Fungi Imperfecti contributed 87.9% of the species isolated. Phycomycetes and Ascomycetes comprised the balance. No Phycomycetes were recovered from either the rhizoplane or macerated roots. This low recovery of Phycomycetes in mangrove habitats is in correspondence with all reports except one. Ascomycetes were isolated from the rhizosphere, the rhizoplane, live roots above the tidal line, and dead roots below the tidal line. Basidiomycetes and Myxomycetes were found only on live prop roots above the tidal line. Eight species of Fungi Imperfecti were predominant in the rhizosphere, rhizoplane and macerated root tissue. Of the Fungi Imperfecti 31.5% were common to the rhizosphere and the rhizoplane; 23.7% common to rhizosphere and macerated root tissue. All the isolates from the macerated root tissue occurred in the rhizoplane. Most of the fungi growing on the roots, and obtained by direct observation, were not recovered by culturing.