Untersuchungen zum Vorkommen von Phagen antagonistisch wirkender Bakterien (biologischer Pflanzenschutzmittel) in der Rhizosphäre der Erdbeere
Final Report Abstract
Verticillium wilt caused by Verticillium dahliae var. longisporum is an important soil-borne disease in different crops. Currently, there are no suitable methods for suppression. Biological control on the basis of beneficial rhizobacteria introduced into the rhizosphere can be a solution. An infection by phages and the influence on establishment and biocontrol activity of these strains in the rhizopshere of plants should be investigated. In the first part of the project the occurrence, persistence and abundance of bacteriophages of Verticillium-antagonists in the rhizopshere of different crops were studied. New antagonists were isolated and served has host strains for phage detection in the same sample. The phages were characterized by their morphology, host range and DNA restriction. A low diversity of antagonists was observed. Mostly the strains belonged to Pseudomonas fluorescence and P. chlororaphis beside Serratia-strains. In contrast a high variety of phages were detected with often unique DNA restriction profiles. In the second part of the study the interactions of phages and their host bacteria were investigated using two model-systems in greenhouse experiments in the rhizopshere of strawberry and oilseed rape, and in a field trial on oilseed rape. The impact of phages on the establishment and biocontrol activity of the host strain population was investigated adding different phage-host ratios onto the plant roots in the presence and absence of the pathogenic fungus. An immediately increase of the number of the naturally occurring phages could be observed with both phage-host systems after application of the biocontrol strain at high densities. In oilseed rape this increase occurred faster in the greenhouse than in the field and was dependent on the initial phage-host ratio. A minimal threshold value of the host bacterial concentration for effective phage multiplication was defined at about 104 CFU g-1 rhizopshere sample. Underneath this threshold value a delayed phage multiplication occurred, especially at a low added phage numbers. A minimal threshold of the phage number was calculated to be about 102 PFU g-1. A significant reduction of the host bacterial concentration was observed in greenhouse and field shortly after phage addition in dependence from the amount of added phages. This was reflected by the plant growth promoting activity of the biocontrol strain in greenhouse in absence of the pathogen. Here the sprout length of the seedlings was promoted by the strain but was reduced in the presence of phages by 15 to 28%. In the presence of the fungus the effect of the BCA on the seedlings and the effect of the phages were completely different. We suggest an influence of the fungus not only on the activity of the BCA but also on the phage. That should be studied in more detail in the future. In greenhouse and field no symptoms of a Verticillium wilt could be detected, thus the effect of the phages on the antifungal activity of the host strains could not be calculated. A potential risk by phages was not sustained for the field. But the effects can be dramatically in greenhouse or growth chambers in dependence of the phage-host system and the fungus of interest. For these applications this kind of study should be done routinely.
Publications
- (2006): Occurrence of bacteriophages of Verticillium-antagonists in the rhizosphere of strawberry. 7th International Workshop on “Plant Growth Promoting Rhizobacteria”. Noordwijkerhout, NL
Wolf, A.
- (2006): Occurrence of bacteriophages of Verticillium-antagonists in the rhizosphere of strawberry. Conference of “International Organisation of Biological and Integrated Control of Noxious Animals and Plants” (IOBC), working group “Biological control of fungal and bacterial plant pathogens”. Spa, Belgium
Wolf, A.
- (2006): Occurrence of bacteriophages of Verticillium-antagonists in the rhizosphere of strawberry. IOBC Bulletin, working group “Biological control of fungal and bacterial plant pathogens” (Spa, Belgium)
Wolf, A.
- (2006): Occurrence of bacteriophages of Verticillium-antagonists in the rhizosphere of various plants. VAAM Jena
Wolf, A.
- (2006): Occurrence of bacteriophages of Verticillium-antagonists in the rhizosphere of various plants. VAAM Jena. Biospektrum
Wolf, A.
- (2006): Zum Vorkommen von Bakteriophagen antagonistisch wirkender Bakterien in der Rhizopshäre verschiedener Nutzpflanzen. Arbeitskreis Biologische Kontrolle der DPG in Geißenheim
Wolf, A.
- (2007): Bacteriophages of Verticillium-antagonists in the rhizosphere of strawberry. Conference of “International Organisation of Biological and Integrated Control of Noxious Animals and Plants” (IOBC), working group “Multitrophic interactions in soil”. Dijon, France
Wolf, A.
- (2007): Bacteriophages of Verticillium-antagonists in the rhizosphere of strawberry. IOBC Bulletin, working group “Multitrophic interactions in soil” (Dijon, France)
Wolf, A.
- (2007): Population dynamics of host bacteria and phages in dependence on the initial phage-host ratio in vitro and in strawberry rhizopshere under greenhouse conditions. Arbeitskreis Biologische Kontrolle der DPG in Graz/Österreich
Wolf, A. and S. Schulze
- (2007): Population dynamics of host bacteria and phages in dependence on the initial phage-host ratio in vitro and in strawberry rhizopshere under greenhouse conditions. VAAM in Osnabrück
Wolf, A. and S. Schulze
- (2007): Population dynamics of host bacteria and phages in dependence on the initial phage-host ratio in vitro and in strawberry rhizopshere under greenhouse conditions. VAAM Osnabrück. Biospektrum
Wolf, A. & Schulze, S.
- (2008): About a biotechnological application of bacteriophages. Guest lecture, University of Xiamen, China
Wolf, A.
- (2009): Population dynamics of host bacteria and phages in the rhizosphere of oilseed rape under greenhouse and field conditions. VAAM Bochum
Wolf, A. & Schulz, F.
- (2009): Population dynamics of host bacteria and phages in the rhizosphere of oilseed rape under greenhouse and field conditions. VAAM Bochum. Biospektrum
Wolf, A. & Schulz, F.
- (2009): Study of a specific phage-host system with a biocontrol host strain in the rhizosphere of oilseed rape. VAAM Bochum
Wolf, A. & Ulbricht, K.
- (2009): Study of a specific phage-host system with a biocontrol host strain in the rhizosphere of oilseed rape. VAAM Bochum. Biospektrum
Wolf, A. & Ulbricht, K.
- (2009): Wechselwirkungen zwischen dem Biokontrollstamm HRO-C48 und einem Phagen im Gewächshaus und im Feld in der Rhizosphäre von Raps. Arbeitskreis Biologische Kontrolle der DPG in Berlin
Wolf, A. & Ulbricht, K.
