The effect of anti-fungal antibiotics on the nodulation of Trifolium subterraneum and the estimation of Rhizobium trifolii populations

Abstract

Three anti-fungal antibiotics (cycloheximide, griseofulvin, and mycostatin) were tested for their effects on inoculated Trifolium subterraneum (subterranean clover). All three influenced the growth and nodulation of the test plant, the effects being least with mycostatin. Mycostatin was further examined for its effect on a plant-infection technique for estimating Rhizobium numbers. The presence in culture media of mycostatin did not impair the accuracy of the plant-infection test for counting rhizobia in a pure culture. Moreover, when the plant-infection technique was used for counting rhizobia in soil, the antibiotic reduced the amount of infection of the test plant by miscellaneous soil micro-organisms, thereby improving nodulation. It is concluded that the incorporation of mycostatin into media (100 p.p.m.) used for growing test plants in plant-infection tests will improve the reliability of the method.