Characteristics of Bacteria from Oilseed Rape in Relation to their Biocontrol Activity against Verticillium dahliae

Abstract

The potential of bacteria that are adapted to the oilseed rape root environment for use in the biological control of Verticillium dahliae, Kleb was investigated in both controlled and non-sterile growth conditions. Bacterial strains dominated by the red-pigmented members of enterobacteriaceae were isolated from thoroughly washed and air-dried root segments of symptomless young rape plants. Other associated strains found either belonged to Alcaligenes sp., Stenotrophomonas spp. and Pseudomonas spp. (Pseudomonas acidovorans and Pseudomonas putida) or were unidenti®ed according to fatty acid methyl ester pro®le analysis. A total of 19 strains isolated in this study together with two previously studied strains, Serratia proteamaculans and Pseudomonas chlororaphis, were characterized on the basis of their interactions with V. dahliae and a number of functional characteristics. In line with earlier observations with root-colonizing fungi also from oilseed rape, all bacterial strains suppressed the pathogen not only directly and but also indirectly in in vitro assays. Mechanisms of suppression were apparently multifold among the strains, but production of hydrogen cyanide does not seem to be involved in indirect inhibition. The majority of the strains possessed the ability to produce cellulases, proteases and phosphatases and some even produced chitinases and induced hypersensitive responses, indicating their potential for nutrient acquisition as well as colonization capacity and active recognition by the plant cells. Investigations in non-sterile ®eld soil revealed that some strains protected rape plants from V. dahliae partly by delaying symptom development. None of the strains, however, was strongly deleterious to rape growth either in the presence or absence of the pathogen. Light microscopic observations of roots and results based on agar printing techniques revealed the potential of the studied strains to colonize or interfere with the pathogen colonization. This study provides some insight into the evolved relationship of bacterial residents with their host in terms of their potential importance in its ®tness. ZusammenfassungMerkmale von Raps isolierter Bakterien in bezug auf ihr Potential zur biologischen BekaÈ mpfung von Verticillium dahliae An den Lebensraum`Rapswurzel' angepaûte Bakterien wurden unter kontrollierten und unter unsterilen Bedingungen hinsichtlich ihres Potentials zur biologischen BekaÈ mpfung von Verticillium dahliae Kleb. gepruÈ ft. Von sorgsam gewaschenen und an der Luft getrockneten Wurzelsegmenten symptomloser junger Rapsp¯anzen wurden BakterienstaÈ mme isoliert, unter denen rot pigmentierte Enterobacteriaceae dominierten. Eine Analyse der FettsaÈ urenmethylesterpro®le ergab, daû die anderen assoziierten StaÈ mme entweder zu Alcaligenes sp., Stenotrophomonas spp. und Pseudomonas spp. (P. acidovorans und P. putida) gehoÈ rten oder aber mit diesem Verfahren nicht identi®ziert werden konnten. Im Rahmen dieser Untersuchung wurden insgesamt 19 StaÈ mme isoliert, die gemeinsam mit zwei zuvor unte...

Verticillium wilt of olive: a case study to implement an integrated strategy to control a soil-borne pathogen

“…On the other hand, while studies on biological control of Verticillium wilts are available, they are again focused in herbaceous hosts and in just a small number of soil-borne fungi (i.e., Talaromyces, Trichoderma) or bacteria (i.e. Bacillus, Paenibacillus, Pseudomonas, Serratia, Streptomyces) species which have so far been demonstrated to be effective BCA against V. dahliae (Jordan and Tarr 1978;Leben et al 1987;Berg et al 1994;Madi et al 1997;Alström 2001;Nagtzaam et al 1998;Narisawa et al 2002;Tjamos et al 2004Tjamos et al , 2005Antonopoulos et al 2008;Uppal et al 2008;Erdogan and Benlioglu 2010;Meschke and Schrempf 2010). Finally, arbuscular mycorrhizal fungi (i.e.…”

Antagonistic Efficacy of Trichoderma harzianum and Bacillus cereus against Ganoderma Disease of Oil Palm via Dip, Place and Drench (DPD) Artificial Inoculation Technique

“…Endophytic bacteria such as Pseudomonas and Bacillus spp. were found to be potent BCAs against fungal pathogens on crops such as cotton, oilseed rape, tomato, cucumber and peas (Chen et al, 1995;Alstrom, 2001). In addition, some members of the genus Bacillus such as B. cereus are often considered as microbial factories of biologically active molecules that are potential inhibitors of fungal growth (Pérez-García et al, 2011).…”

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