Pathogen genetic diversity varies in response to environmental changes. However, it remains unclear whether plant barriers to invasion could be considered a genetic bottleneck for phytopathogen populations. Here, we implement a barcoding approach to generate a pool of 90 isogenic and individually barcoded Ralstonia solanacearum strains. We used 90 of these strains to inoculate tomato plants with different degrees of physical permeability to invasion (intact roots, wounded roots and xylem inoculation) and quantify the phytopathogen population dynamics during invasion. Our results reveal that the permeability of plant roots impacts the degree of population bottleneck, genetic diversity, and composition of Ralstonia populations. We also find that selection is the main driver structuring pathogen populations when barriers to infection are less permeable, i.e., intact roots, the removal of root physical and immune barriers results in the predominance of stochasticity in population assembly. Taken together, our study suggests that plant root permeability constitutes a bottleneck for phytopathogen invasion and genetic diversity.

病原体遗传多样性随环境变化而变化。然而，目前尚不清楚植物入侵屏障是否可以被视为植物病原体种群的遗传瓶颈。在这里，我们采用条形码方法来生成 90 个同基因且单独条形码的Ralstonia solanacearum菌株库。我们使用其中的 90 个菌株来接种具有不同程度的入侵物理渗透性的番茄植株（完整根、受伤根和木质部接种），并量化入侵期间植物病原体种群动态。我们的结果表明，植物根系的渗透性影响罗尔斯通尼亚种群的瓶颈程度、遗传多样性和组成。我们还发现，当感染屏障渗透性较差时（即完整的根），选择是构建病原体种群的主要驱动力，根物理和免疫屏障的消除导致种群组装中随机性占主导地位。综上所述，我们的研究表明植物根部渗透性构成植物病原体入侵和遗传多样性的瓶颈。