Figure 1.
Description of the experiment. Day 1, surface-disinfected seeds were transferred to Petri dishes containing 1% water agar and were incubated in a growth chamber to allow seed germination. Day 3, seeds were treated with sterile MgSO4 (mock-inoculated) or inoculated with a bacterial suspension of Paraburkholderia phytofirmans PsJN (PsJN) or Enterobacter sp. 32A (32A) by overnight incubation in the growth chamber. Day 4, germinated seeds with the same root length were selected and each seed was transferred to a sterile glass tube containing half-strength Hoagland. Day 7, a freshly emerged mirid adult (Macrolophus pygmaeus or Nesidiocoris tenuis) was placed in each glass tube containing a tomato plant that was either mock-inoculated or inoculated with PsJN or 32A. Before transferring the mirid in the glass tube, shoot length was measured by image analysis. Tubes were incubated in the growth chamber in order to allow mirids to feed on tomato plants (acquisition period). Day 11, for double labelling of the oligonucleotide probes for fluorescence in situ hybridisation (DOPE-FISH) analysis, mirids were collected at the end of the acquisition period on mock-inoculated plants or plants inoculated with PsJN or 32A, shoot length was measured by image analysis, and whole plants were collected for bacterial re-isolation and fresh weight assessment. Each mirid was transferred to a new glass tube containing a mock-inoculated tomato plant and incubated to allow the mirids to feed on the tomato plants (mirid-mediated transmission), and then shoot length was measured. Day 14, mirids and plants after mirid-mediated transmission were collected for bacterial re-isolation, and the tomato shoot length and fresh weight were assessed.