Rice is global staple food consumed worldwide. Thai jasmine rice (Oryza sativa KDML
105) is Thailand most important economic crop. However, the prevalence of Bakanae diseases
from fungal pathogen Fusarium fujikuroi is the major problem for rice cultivation in Thailand.
The disease affects both quantity and quality of rice resulting in the decreasing of rice yield.
Large volume of harmful chemical substances is being used to control the outburst of Bakanae
disease. In this study, two selected mangrove Streptomyces were tested for their plant growth
promoting activities and growth inhibiting activity on F. fujikuroi. In vitro experiments indicated
that, isolate S2-SC16 is the most effective to inhibit the germination of F. fujikuroi CMU-F02
conidia. In vivo experiment also demonstrated an ability of Streptomyces isolate S2-SC16 to control
F. fujikuroi CMU-F02 infection in rice seeds as the seed infected percentage is reduced from
23% to 6%. Furthermore, in pot experiment, isolate S2-SC16 not only shows an ability to restrict
the infection of F. fujikuroi CMU-F02, but also shows an ability to promote the growth of rice
seedlings by increasing numbers of growth parameters including root length, shoot height, leaf
width and weight. Phylogenetic analysis based on 16S rRNA gene sequence indicated that isolate
S2-SC16 is closely related to Streptomyces iranensis HM 35T (99.55% similarity). From the results
of our study, there is the possibility of using mangrove actinomycetes as plant growth promoting
and alternative environmental friendly control agents for Bakanae disease in Thai jasmine rice
KDML 105. S. iranensis isolate S2-SC16 is a candidate for the development as plant supplement
and biocontrol agent.