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.