ROOT-COLONIZATION ABILITY OF ANTAGONISTIC STREPTOMYCES-GRISEOVIRIDIS

Root-colonization ability of Streptomyces griseoviridis was tested on turnip rape (Brassica rapa subsp. oleifera) and carrot (Daucus carota) by the plate test and the sand-tube method. In the plate test, coloni zed root length of total root length was highly significantly greater for turnip rape roots (72%) from those for carrot roots (1%). In the s and-tube method, root-colonization ability was examined in nonsterile soil, and no water was added after sowing. Seeds were treated with spo res of S. griseoviridis or the biofungicide Mycostop. Roots were cut i nto 2-cm segments, and the root segments and the rhizosphere soil were studied separately. Root-colonization frequencies and population dens ities of the microbe in the rhizosphere soil indicated that S. griseov iridis successfully colonized turnip rape but weakly colonized carrot. Root-colonization of turnip rape is accounted for as proliferation of S. griseoviridis in the rhizosphere of turnip rape seedlings and is n ot due to the movement of microbe through the rhizosphere by water inf iltration.