Kill or cure? The interaction between endophytic Paenibacillus and Serratia strains and the host plant is shaped by plant growth conditions
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Verticillium wilt is difficult to suppress, and causes severe yield losses in a broad range of crops. Five Serratia and five Paenibacillus endophytic isolates showing antagonistic properties against fungal pathogens were compared for their plant growth-promoting (PGP) potential under different plant growth conditions with the objective of evaluating the PGP of endophytic strains in different ad planta systems.
Preselected isolates were applied to the surface-sterilized seeds of oilseed rape and cauliflower using bio-priming. The isolates’ PGP effect and root colonization capacities were compared under gnotobiotic conditions. One strain from each genus was selected and tested for its PGP qualities in sterile and non-sterile soil.
Serratia treatment resulted in different levels of PGP, while Paenibacillus strains damaged roots under gnotobiotic conditions. P. polymyxa Sb3-1 did not have a significant effect on plant growth in non-sterile soil; however it did promote plant growth in the sterile soil. S. plymuthica 3RP8 and P. polymyxa Sb3-1 were selected for further testing of their biocontrol effect under field conditions.
The choice of growth environments in the investigation of plant-bacterium interaction is crucial. Non-sterile soil is suggested as the ideal medium for use in studying the PGP effect.
KeywordsBiocontrol Bio-priming Plant growth promotion PGP BIOCOMES Brassica Serratia Paenibacillus Verticillium wilt
The authors would like to thank Timothy Mark (Graz) for English revision and discussion. This project was funded by the European Union in frame of FP7-KBBE-2013-7-single-stage (BIOCOMES; No. 612713) and by the Austrian Research Promotion Agency (FFG; No. 836466). The authors gratefully acknowledge support from NAWI Graz. We thank Christin Zachow (Graz) for her help regarding experimental questions and Anastasia Bragina (Graz) for help regarding statistical issues.
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