With the improper application of fungicides, Phytophthora sojae begins to develop resistance to fungicides, and biological control is one of the potential ways to control it. We screened two strains of Bacillus; Bacillus amyloliquefaciens JDF3 and Bacillus subtilis RSS-1, which had an efficient inhibitory effect on P. sojae. They could inhibit mycelial growth, the germination of the cysts, and the swimming of the motile zoospores. To elucidate the response of P. sojae under the stress of B. amyloliquefaciens and B. subtilis, and the molecular mechanism of biological control, comparative transcriptome analysis was applied. Transcriptome analysis revealed that the expression gene of P. sojae showed significant changes, and a total of 1616 differentially expressed genes (DEGs) were detected. They participated in two major types of regulation, namely “specificity” regulation and “common” regulation. They might inhibit the growth of P. sojae mainly by inhibiting the activity of ribosome. A pot experiment indicated that B. amyloliquefaciens and B. subtilis enhanced the resistance of soybean to P. sojae, and their control effects of them were 70.7% and 65.5%, respectively. In addition, B. amyloliquefaciens fermentation broth could induce an active oxygen burst, NO production, callose deposition, and lignification. B. subtilis could also stimulate the systemic to develop the resistance of soybean by lignification, and phytoalexin.

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To explore genetic differentiation and the genetic relationships of Phytophthora sojae in Anhui Province, the inter-simple sequence repeat (ISSR) technique was used to analyze the genetic diversity of P. sojae. One hundred and sixty ISSR fragments were observed, including 129 (80.6%) polymorphic bands. This suggested that abundant genetic diversity existed among P. sojae in Anhui Province. The pairwise genetic similarity coefficients among the 62 strains ranged from 0.72 to 0.96, with a mean value of 0.85, indicating that there was a high level of genetic variation. Phytophthora sojae strains were divided into five clusters based on neighbor-joining (NJ) analysis, and the clustering was not related to geographic source, according to Mantel’s test (r = 0.3938). In addition, the clustering of strains from the same geographical source had little relationship to the year of collection. Analysis of molecular variance (AMOVA) showed that 16.65% of the genetic variation was derived from the collection area and 83.35% of the genetic variation was within-population variation. The genetic flow between different geographical sources ranged from 0.623 to 2.773, with a mean of 1.325, suggesting that gene exchange was frequent. Genetic distance and the genetic differentiation coefficient were not related to spatial distance.

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Phytophthora sojae is a devastating pathogen of soybean [Glycine max (L.) Merr.] that causes Phytophthora root and stem rot (PRR) on soybean plants worldwide. The pathogen leads to evident differentiation of pathogenicity which brings some difficulties to the control of the disease. Soybean germplasm plays an important role in disease resistance to P. sojae. To understand the role of soybean in the pathogen differentiation of P. sojae, transcriptome sequencing and biological information technology were used to analyse the difference in transcriptional level of soybean response to P. sojae infection by two isolates BB8 and BZ9 with different pathogenicity. A total of 1596 differentially expressed genes (DEGs) were screened from the soybean plants treated with the strong pathogenic isolate BB8 and weak pathogenic isolate BZ9, of which 256 were upregulated and 1340 were downregulated in BZ9 treated samples. Gene Ontology analysis revealed that the highly enriched terms annotated in biological processes were metabolic process, cellular process and single-organism process. Kyoto Encyclopedia of Genes and Genomes pathways were distributed primarily in metabolism, environmental information processing and cellular processes. Photosynthesisantenna proteins, photosynthesis, phenylpropanoid biosynthesis, carbon fixation in photosynthetic organisms, plant hormone signal transduction, flavonoid biosynthesis, carbon metabolism and nitrogen metabolism were the most substantial metabolic pathways. Ten candidate DEGs were selected and their expression levels were detected via fluorescence quantitative polymerase chain reaction. The expression trends were basically consistent with the results of RNA-seq detection, confirming the reliability of RNA-seq data. Taken together, this was the report on the transcriptome analysis of soybean in response to P. sojae using high-throughput sequencing. A number of DEGs and pathways were discovered, which provided valuable information for obtaining high-quality soybean resistance resources.