Einfluß der Behandlung von Rübensaatgut mit Rhizosphärebakterien auf den Befall durch Pilze der Gattung Pythium II. Untersuchungen zum Wirkungsmechanismus

Abstract The influence of a seed-dressing with rhizosphere bacteria on the infection of sugarbeet by fungi of the genus Pythium II. Studies on the mode of action
Studies were conducted to determine the mode of action responsible for the reduction of Pythium infection of sugarbeet seedlings caused by an inoculation with rhizosphere bacteria. It was shown that the bacteria reduced Pythium ultimum , sporangia germination. More detailed studies with the bacterial isolate T58 demonstrated that activity was related to both presence of the living bacteria as well as to inoculum density.
Water soluble extracts from the seed of different sugarbeet cultivars stimulated P. ultimum sporangia germination to different degrees, Germination, however, decreased as the density of the fluorescent pscudomonad T58 was increased. Reductions in mycelial growth, caused by a number of isolates, indicated the presence of antibiotic activity.
The addition of high levels of iron to the substrate caused a reduction in the level of antagonism of two pseudomonad isolates on the seed of the cultivar Kawevera. The rate of reproduction of two bacterial isolates was slower on extracts from the seeds of the cultivar Primahill than on the cultivar Kawevera. Rhizobacteria colonization of the root as well as the hypocotyl was observed with one isolate.