Studies on Communities of Endophytic Actinomycetes from Rice and Their Antipathogenic Activities In vitro

This is the first report of filamentous actinobacteria isolated from surface-sterilized root and leave tissues of healthy rice plants. The isolation, characterization and analysis of the populations of endophytic actinomycetes were carried out on four rice cultivars in Panyu district and Wushan district in Guangdong province, South China. For all the different rice cultivars from the two sites, most endophytic actinomycetes is Streptomyces, among which Streptomycetes griseofuscus constitute the preponderant actinomycetes accounting for 36.1% to 69%. The distributions of endophytic actinomycetes in roots and leaves were different, some were organ-specific. More diverse endophytic actinomycetes were isolated from roots than from leaves. The diversity of the endophytic actinomycetes in Wushan was less than that in Panyu. The alkaline soil in Panyu is better for the growth and colonization of actionmycetes. The results suggested that differences in chemical composition of soil could influence the endophytic microbial communities of rice plants. More diverse endophytic actinomycetes were isolated from poor-growing seedlings and susceptible rice cultivars than from the disease-resistant counterparts. Endophytic actinomycetes have been successfully re-isolated after rice seedings inoculation. Streptomyces griseofuscus could not only colonize on interior and exterior of the rice roots but on the stem and leaves as observed with scanning electron microscopy. In the dual culture and activities detection of the metabolites, 50% of all the isolated endophytic actinomycetes showed antagonistic to rice pathogens. Streptomyces griseofuscus, the greatest part of all the antagonistic communities, reached 55.4% of all the active actinomycetes. These active endophytes inside the plants have intimate correlation with their host, they may play an important role in the development,physiology and defense-response of rice.