Microbispora Dominate Diversity of Endophytic Actinobacteria from Australian Rice Plants

A study to detect the diversity of endophytic Actinobacteria from Australian rice was conducted using culture-dependent and culture-independent methods. Rice samples were collected from the rice growing area near Yanco, New South Wales, Australia. Isolation of the endophytic Actinobacteria was done over two consecutive growing seasons. The results demonstrated that most isolates were obtained from plants 10 weeks and older, and only a few were found in younger plants. Microbispora spp. were the most commonly isolated endophytic Actinobacteria (94%) with Streptomyces spp. and other genera present at lower numbers (6%). The culture-dependent method findings were confirmed by T-RFLP profile analysis. Restriction digests using HhaI and RsaI also showed an abundance of terminal restriction fragments (TRFs) profiles related to the genus Microbispora. Furthermore, other biological properties of the endophytic Actinobacteria isolates were also determined. Four isolates, Saccharothrix OSH21, Saccharopolyspora OSR26, Streptomyces OSR46 and Microbispora OSR61, were found to suppress the growth of the pathogenic fungus Rhizoctonia solani. Moreover, these isolates might be able to promote plant growth by producing indole acetic acid or to solubilise phosphate making this nutrient available for plant uptake.