Fig. 4: Positive selection pressure sites facilitate the adaptability of Phytophthora sojae to soybean.

a Schematic comparison of various XEG1 and XLP1 mutants across multiple Phytophthora genomes. Each row represents a different genome, and mutation sites are highlighted in green, positive selection sites are indicated with dark gray, and missing sequences are displayed in light gray. Detailed mutation information is available in Supplementary Data 4. b, c Positive selection pressure sites enable the pathogenicity of P. sojae. d Natural mutation sites of P. sojae isolates. A map depicting the geographic distribution of P. sojae single nucleotide polymorphisms (SNPs). Variations in PsXEG1 and PsXLP1 across homozygous and heterozygous mutant SNPs are presented for each isolate. Detailed mutation information is provided in Supplementary Data 5. e, f Positive selection pressure site 62 in P. sojae population isolates enables the pathogenicity of P. sojae. b, e Representative images of disease symptoms were photographed at 48 hpi. c, f Relative biomass of mutant strains and wild-type at 48 hpi was quantified using genomic DNA qPCR. In the box plots, dots represent min-to-max value of individual data points (n = 9 biological replicates), the line indicates the median, and the box boundaries indicate the 25th and 75th percentiles. Statistical differences were assessed using Duncan’s multiple range test, with different letters indicating significant differences (p < 0.01). Source data are provided as a Source Data file. g Model: XEG1 and XLP1 originated within the Phytophthora genus. Over time, evolutionary differentiation within the genus led to the development of XEG1 and XLP1 from ancestral genes across various Phytophthora species. Genus-specific selection pressures acting on the XEG1/XLP1 gene pair have been pivotal for host adaptation and are strongly associated with the variability of Phytophthora host ranges.