繁殖体数量对外来Ralstonia solanacearum 在红壤中入侵潜力的影响

外来种的繁殖体压力因可调控其他入侵影响因素(如外来种特性)而备受入侵生态学家的关注。前人研究指出剂量-响应曲线能够定量分析繁殖体数量对入侵潜力的影响，但关于该曲线形状的认识尚未统一。利用土壤微宇宙，比较了初始接种量为10³（PP3）、10⁵（PP5）、10⁷（PP7）和10⁹ CFU·g^-1（PP9）的青枯病菌Ralstonia solanacearum进入土壤3 和42 d后的存活量，并对初始接种量和存活量之间关系进行拟合，试图探清地下部微生物入侵的剂量-响应曲线状况。研究发现，不同接种量处理外来R. solanacearum接入土壤3 d后的存活量差异显著（P<0.05），从大到小依次为PP9、PP7、PP5和PP3，初始接种量和存活量之间拟合的剂量-响应曲线为指数型；而外来Ralstonia solanacearum接入土壤42 d后，除了初始接种量为10⁹ CFU·g^-1处理的存活量稍高外，其余处理间差异不显著，此时的剂量-响应曲线呈直线型（斜率约为0）。结果表明，外来病原菌入侵土壤时的剂量-响应关系会随其进入土壤时间的延长而改变，前期为指数型，后期转为直线型，这说明外来R. solanacearum在红壤中的入侵潜力在入侵前期随繁殖体数量增加而呈指数增长，在入侵后期不受繁殖体数量的影响。

Effect of propagule pressure of non-indigenous Ralstonia solanacearum on its invasion potential in soil

Propagule pressure is one of fundamental factors to influence invasion success, yet our knowledge of its role in the microorganism domain is limited. Moreover, dose-response curve has been considered as an effective way to describe the influence of propagule number on macro-organism invasion, but it still different to draw generalizable conclusions about the type of the curve. Here, we carried out a soil microcosm experiment to compare the survival of non-indigenous Ralstonia solanacearum with four different inoculum levels (10³, 10⁵, 10⁷ and 10⁹ CFU·g^-1 dry soil) on the day 3 and day 42 after introducing them into the tested soil. Also, fitting was conducted on the data of initial inoculum size and survival of each sampling time. The results showed that the inoculum size had significant impact on the survival of non-indigenous bacteria on day 3, but not for the survival of non-indigenous bacteria on the day 42. In addition, the dose-response curve maintained exponential type and horizontal type on day 3 and day 42 after introduction, respectively. Therefore, the type of dose-response curve of non-indigenous soil-borne bacteria invasion was various in different incubation time, and it was concluded that invasion potential of non-indigenous Ralstonia solanacearum in red soil was increased exponentially with the increase of its propagule number at the early invasion stage, but no change at the late invasion stage.