RESEARCH ARTICLE Improvement of seed bio-priming of oilseed rape (Brassica napus ssp. oleifera) with Serratia plymuthica and Pseudomonas chlororaphis Ruba Abuamsha, Mazen Salman and Ralf-Udo Ehlers* Institute for Phytopathology, Department of Biotechnology and Biological Control, Christian-Albrechts-University, Hermann Rodewald Str. 9, 24118, Kiel, Germany (Received 24 May 2010; returned 6 July 2010; accepted 1 November 2010) Seed bio-priming of oilseed rape (Brassica napus) with the antagonistic rhizobacteria Serratia plymuthica and Pseudomonas chlororaphis was improved. With the imbibition of water, bacteria are transported into the seed where they survive better. To obtain a minimum bacterial density in the seed of log 10 5 colony-forming-units (CFUs) seed 1 , the bacterial density in the bio-priming suspension should be log 10 9 CFUs mL 1 for S. plymuthica and log 10 8 CFUs mL 1 for P . chlororaphis. Priming duration was reduced from 12 to 2 h for S. plymuthica and 4 h for P . chlororaphis . Among other priming solutions tested, the addition of MgSO 4 best supported establishment in the seeds and also improved germination. The optimal bio-priming temperature for S. plymuthica is 288C and for P . chlororaphis 228C. Survival of the bacteria inside the seeds was moderately improved by storage at low temperature but considerably prolonged by storage under anaerobic conditions. P . chlororaphis survived significantly longer than S. plymuthica. Keywords: seed treatment; germination; biological control; survival; storage conditions Introduction Oilseed rape (OSR) (Brassica napus L. ssp. oleifera) has become one of the most important oil crops grown in many parts of the world, including Canada, China and Europe. The plant is susceptible to several fungal pathogens, like Leptosphaeria maculans (Desmo.) Ces & de Not. (anamorph Phoma lingam Tode ex Fr.) (blackleg disease) and Sclerotinia sclerotiorum (Lib.) de Bary (stem rot), which can be controlled by application of fungicides (Fitt et al. 1997; Fitt, Brun, Barbetti, and Rimmer 2006). Soil-borne pathogens, like Verticillium longisporum (ex. V. dahliae var. longisporum Stark, comb. nov. Karapapa) (Verticillium wilt) and Plasmodiophora brassicae Woronin (Clubroot), cannot be controlled by chemical means. With the increasing frequency of OSR in the crop rotation, the problems with soil-borne pathogens augment. Due to the development of fungicide resistance or sub-optimal timing of fungicide application, leave and stem diseases can also cause severe yield losses (West, Kharbanda, Barbetti, and Fitt 2001). Micro-organisms can be used to control plant diseases (e.g., Harman 1991; Gerhardson 2002). Many of the antagonists colonize the rhizosphere (Berg, Fritze, *Corresponding author. Email: ehlers@biotec.uni-kiel.de Biocontrol Science and Technology , Vol. 21, No. 2, 2011, 199213 ISSN 0958-3157 print/ISSN 1360-0478 online # 2010 Taylor & Francis DOI: 10.1080/09583157.2010.537311 http://www.informaworld.com Downloaded By: [Ehlers, Ralf-Udo] At: 13:13 17 December 2010