[Obstacles of soybean continuous cropping, III. Mechanism of soybean yield increment by marine actinomyces MB-97].
An isolate of marine actinomyces MB-97 identified as Streptomyces microflavus could successfully colonize in the rhizoshpere of soybean, and inhibit Penicillium purpurogenum, a soybean deleterious rhizospheric microorganisms. After applied MB-97, the ratio of bacteria/fungi in the rhizosphere of soybean was increased, and the soil became to be "Bacterial type" from "Fungal type". The populations of P. purpurogenum were apparently suppressed about 80%, and the harm of toxins in soil was weak. The soybean root rot caused by soilborne fungi such as Fusarium was decreased 50%, and MB-97 could stimulate the growth of soybean seedlings. In field study, the mean yield of soybean raised by 15.2%, implying that Streptomyces microflavus was an effective plant growth-promoting rhizobacteria on soybean.