Studies on the selection of streptomycetes in the rhizoplane of sugar-cane.

The overwhelming majority of species of Streptomyces (S. aburaviensis, S. chromofuscus, S. collinus, S. tenebrarius, S. galilaeus, etc.) and Streptoverticillium aureoversales indigenous in the cultivated horizon of the red ferralitic tropical soil of an investigated sugar-cane plantation, were completely lacking in the root surface region of this plant. Only two species (S. griseorubiginosus and S. viridochromogenes) characterized by very broad C- and N-source utilization spectra, proved capable of colonizing the roots of sugar-cane under natural circumstances. They are not stable members of the rhizoplane but, in contrast to many other species of Streptomyces, are very successful occasional root colonizers. S. viridochromogenes occurred also in the root far soil region but S. griseorubiginosus could only be detected in the rhizoplane.