Promotion of growth and health of Styrian oil pumpkins (Cucurbita pepo var. styriaca) by bacterial broad-spectrum antagonists

Due to increasing yield losses of Styrian oil pumpkins caused by the fungus Didymella bryoniae and bacterial pathogens, it was aimed to control this multi-pathogen disease by biological means. Out of 2320 microbial isolates of oil pumpkin-associated bacteria and fungi, six strains with a broad-spectrum antagonistic potential against respective oil pumpkin pathogens were selected and applied to the seeds. Effects of the bacterial inoculants, with and without additional chemical seed treatment, on plant growth and health were evaluated in three field trials. The treatments showed different effects against fungal diseases: no effect on fruit rot was observed, whereas powdery mildew was suppressed by Paenibacillus polymyxa PB71 and Lysobacter gummosus L101 in 2010. In addition, both bacteria increased seed yield in all three field trials. Application of Serratia plymuthica S13 resulted in increased seedling emergence, up to 109% in comparison to the control treatment in 2011. Furthermore, some treatments resulted in drought tolerance and increased seed weight. The promising bacterial inoculants will continue to be tested under field conditions, in order to develop a biological product supporting the productivity of the Styrian oil pumpkin crop.