Isolation and characterization of Bacillus altitudinis JSCX-1 as a new potential biocontrol agent against Phytophthora sojae in soybean [Glycine max (L.) Merr.]

Aims Phytophthora root and stem rot caused by the oomycete plant pathogen Phytophthora sojae (Kaufmann & Gerdemann), is a destructive disease of soybean [Glycine max (L.) Merr.]. There is no straightforward available method to control this disease. The present study aimed to isolate a biocontrol agent (BCA) to control Phytophthora rot and gain insights into the mechanisms of biocontrol activity. Methods Antagonistic bacteria screening, inoculation assays, histochemical and fluorometric staining and real-time polymerase chain reaction (RT-PCR) were used to achieve the goals of the present study. Results The results indicated that the isolated BCA strain JSCX-1 was characterized as Bacillus altitudinis. Further studies showed that JSCX-1 bacterial filtrate inhibited the mycelial growth and zoospore germination of P. sojae. Greenhouse experiments showed that biocontrol efficiency of JSCX-1 against P. sojae was 49.28 +/- 3.42%. Our results revealed that JSCX-1 increased the reactive oxygen species (ROS) production and callose deposition of soybean leaves. Moreover, JSCX-1 up-regulated the transcriptional level of the G. max PR1a gene but not that of the LOX and ERF genes. Conclusions B. altitudinis JSCX-1 can effectively reduce the infectivity of P. sojae via increasing the ROS production and callose deposition on soybean, and up-regulating the expression of salicylate-responsive gene GmPR1a.