Interaction of soil bacteria, mycorrhizal fungi and orchid seed in relation to germination of Australian orchids

Abstract

SUMMARYEndotrophic bacteria were isolated from the mycorrhizal tissues of 12 out of 13 tested species of Western Australian terrestrial orchids. The bacteria were placed into eight groups based on u.v. light fluorescence, Gram staining and colony characteristics. The most commonly isolated bacteria from 9 out of the 12 orchid species sampled were strains within the Pseudomonas fluorescens‐putida group. The abundance of bacteria followed a seasonal pattern that differed between orchid genera especially on the basis of the morphology of fungus infected tissue. There was little evidence of specificity of bacterial groups to orchid taxa or part of the plant infected by the fungus. Symbiotic germination of Pterostylis vittata seed in association with seven bacterial isolates showed a significant promotion of germination and seedling development with three bacterial strains. The influence of a fourth strain was no different to the control while the remaining three strains significantly suppressed seedling development.