Screening and identification of a marine bacterium strain SH-27 against phytophthora capsici causing pepper phytophthora blight

Abstract:

[Background] Pepper Phytophthora blight, caused by Phytophthora capsici, is one of the most devastating diseases of pepper growing areas worldwide. Biological control has drawn more and more attention in recent years for its safety to environment, human and animal. [Objective] To screen and identify a marine bacterium strain SH-27 against phytophthora capsici and study its effects on disease control and growth promotion on pepper. [Methods] Antagonistic marine bacteria were isolated by serial dilution and dual culture. The effects of controlling disease and growth promotion on pepper seedlings were studied by using the fermentation broth of strain SH-27. Strain SH-27 was identified by morphological characteristics, physiological and biochemical tests and 16S rRNA and gyrA gene sequence analysis. [Results] A total of 142 bacterial isolates were obtained. Among them, 11 strains displayed the antagonistic activity to Phytophthora capsici. Especially strain SH-27 isolated from corals displayed high antagonistic activity and broad antimicrobial spectrum. Pot tests showed that the root length, plant height, stem diameter, fresh weight and dry weight of pepper plant treated with SH-27 fermentation broth were promoted significantly when compared to the control treatment. The control efficacy of strain SH-27 to pepper phytophthora blight were 70.81%, 66.55% and 48.20% when the pathogens were inoculated after 4, 6 and 9 days respectively. Based on characteristics in morphology, physiology, biochemistry, 16S rRNA and gyrA gene sequence analysis, strain SH-27 was identified as Bacillus amyloliquefaciens. [Conclusion] Due to its effects of disease control and growth promotion on pepper, strain SH-27 is possible to be further developed as an excellent strain for microbial fertilizer and fungicide.