Influence of temperature on the motility of Pseudomonas oryzihabitans and control of Globodera rostochiensis F.I. Andreoglou a , I.K. Vagelas a , M. Wood b, * , H.Y. Samaliev c , S.R. Gowen a a Department of Agriculture, The University of Reading, Earley Gate, P.O. Box 236, Reading, Berkshire RG6 6AT, UK b Department of Soil Science, The University of Reading, Whiteknights, P.O. Box 233, Reading, Berkshire RG6 6DW, UK c Department of Entomology, 12 D. Mendeleev Str., Agricultural University, Plovdiv 4000, Bulgaria Received 27 February 2002; received in revised form 15 January 2003; accepted 24 April 2003 Abstract The motility and efficacy of Pseudomonas oryzihabitans as a biocontrol agent against the potato cyst nematode Globodera rostochiensis were studied with respect to temperature. The influence of soil moisture on bacterial movement was also tested. In a closed container trial, P. oryzihabitans significantly reduced invasion of second stage juveniles (J2) of G. rostochiensis in potato roots, its effect being more marked at 25 and 21 8C than at 17 8C. P. oryzihabitans motility in vitro was optimal at 26 8C and inhibited at temperatures below 18 8C. In soil, both temperature and matric potential affected bacterial movement. At 16 8C its movement and survival were suppressed, but they were unaffected at 25 8C. At both temperatures the biocontrol agent moved faster in the wetter (2 0.03 MPa) than in the drier soil (2 0.1 MPa). These results suggest that temperature is a key factor in determining the potential of P. oryzihabitans as a biocontrol agent. q 2003 Elsevier Science Ltd. All rights reserved. Keywords: Matric potential; Temperature; Pseudomonas oryzihabitans; Globodera rostochiensis; Potato cyst nematode; Invasion 1. Introduction Entomopathogenic nematodes have been observed to suppress populations or reproduction of plant parasitic nematodes. The mechanism of action causing suppression appears to be largely related to biostatic or repellent substances derived from the bacterial associates of nematodes (Georgis and Kelly, 1997; Jagdale et al., 2002). Such bacteria produce antimicrobial metabolites under in vitro and in vivo conditions, some of which have shown selective nematicidal activity (Hu et al., 1999; Grewal et al., 1999). Pseudomonas oryzihabitans, which is motile by means of a single polar flagellum, was isolated from Steinernema abbasi (Elawad et al., 1999), a new species of Steinerne- matid recovered from soil in the Sultanate of Oman (Elawad et al., 1997) and so far it has shown promising results as a potential biocontrol agent against plant parasitic nematodes. In laboratory experiments, it inhibited hatching and immobilised second stage juveniles (J2) of the potato cyst nematode Globodera rostochiensis and the root-knot nematode Meloidogyne javanica possibly due to the production of secondary metabolites (Andreoglou et al., 2000; Samaliev et al., 2000). In soil, it prevented invasion of M. javanica J2 in tomato roots and interfered with nematode development in galls (Samaliev et al., 2000). Subsequent studies showed that the bacterium was able to colonise tomato roots, where it probably produced secondary metabolites, which acted against J2 (Andreoglou, F.I., 2001. Control of the potato cyst nematode Globodera rostochiensis with Pseudomonas oryzihabitans, PhD Thesis, The University of Reading, Reading, UK). Root colonisation includes dispersal of microorganisms from a source of inoculum to the actively growing root and multiplication or growth in the rhizosphere (Parke, 1991). This involves passive transport on the root apex, passive movement with percolating soil water and active motility. The relative contribution of each component may depend on variables including the rate of root growth, soil texture, soil temperature and moisture characteristics, and attributes of the microorganisms such as growth rate, motility, chemo- taxis and cell surface properties. 0038-0717/03/$ - see front matter q 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0038-0717(03)00157-3 Soil Biology & Biochemistry 35 (2003) 1095–1101 www.elsevier.com/locate/soilbio * Corresponding author. Tel.: þ44-118-931-6557; fax: þ 44-118-931- 6660. E-mail address: m.wood@reading.ac.uk (M. Wood).