Objective Endophytic bacteria that could effectively control the copper blight, one of the most significant diseases that seriously infects the seedlings and saplings, of Chinese fir (Cunninghamia lanceolate) were investigated.
Methods Candidate endophytic bacteria were cultured and isolated from leaves of Chinese fir followed by morphological, physiological, and biochemical analyses as well as 16S rRNA sequencing for identification. Pathogen inhibition against Pestalotiopsis apiculatus by the sterile fermentation filtrate of potential specimens was tested on toxic plate and Oxford cup and observed under a microscope. Effectiveness of the disease control by the selected bacteria was further verified in vitro on fir leaves.
Results The endophytic bacterium coded SM-1 showed a significant antagonistic effect against P. apiculatus. It was isolated and identified as Bacillus atrophaeus. On the toxic plate and Oxford cup tests, the SM-1 fermentation filtrate yielded a P. apiculatus inhibition rate of 58.80%. Morphologically, the bacterium inhibited the mycelial growth and caused cellular swelling that changed the cells spherical in appearance of the pathogen. The efficacy of the SM-1 filtrate on copper blight on the fir leaves was 95% with significantly reduced disease severity (P＜0.01).
Conclusion The SM-1, identified as B. atrophaeus, appeared to be a potential biocontrol agent to deter copper blight on Chinese fir.
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