Promotion of growth, health and stress tolerance of Styrian oil pumpkins by bacterial endophytes

Substantial yield losses of Styrian oil pumpkin caused by the fungus Didymella bryoniae and bacterial pathogens were recently reported. Here we applied bacterial endophytes with a broad antagonistic activity to pumpkin plants by seed priming. Effects of the bacterial inoculants with and without chemical seed treatments on plant growth and health were evaluated during three different field trials in two consecutive years (2010 and 2011). Biological seed treatments strongly supported the germination of pumpkin seeds. In 2010, the germination of the biologically treated seeds was comparable to the rate following a chemical treatment; whilst in 2011 effects of biological seed treatments were more obvious, including an increased emergence rate up to 109?% by Serratia plymuthica S13. Furthermore, tolerance against desiccation stress was observed for Serratia as well as for Lysobacter gummosus L101 treatment. The biological treatment showed different effects against fungal diseases: no effect on fruit rot was observed, whereas powdery mildew could be significantly suppressed by Paenibacillus polymyxa PB71 and L. gummosus L101 in 2010. In addition, both strains led to reproducible increases in harvest yields. In this study, we found bacterial endophytes suitable as inoculants for plant growth promotion, biocontrol, as well as for enhancing stress tolerance in Styrian oil pumpkins.