Azorhizobium [217] Bradyrhizobiurn [218] ¢ Rhizobium [219] d A. caulinodans [217] B. japonicurn [218] Bradyrhizobium sp. ( Parasponia ) R. fredii [220] ( Sinorhizobium fredii ) R. galegae [222] R. leguminosarum biovar phaseoli [223] biovar trifolii [223] biovar viciae [223] R. loti [224] R. meliloti [219] d R. tropici ~ [225] Sinorhizobium [24] g S. fredii [24] R. japonicum (slow growing strains) [219] d R. japonicum (fast growing strains) [221] R. phaseoli [219] a R. trifolii [219] d R. legurninosarum [219] d R. leguminosarum biovar phaseoli (type II strains) [225] d Sesbania Glycine, ~gna Glycine, ~gna Galega Phaseolus Trifolium Pisum, l, qcia Lotus, Lupinus Melilotus, Medicago Phaseolus, Leucaena Rhizobium sp. strain Leucaena, NGR234 [226] f Macroptilium, Vigna R. fredii [220] Glycine a Only species relevant for this review are listed. b The list of host plants is not complete. The host range may extend beyond that given here and may differ among species of a genus. c For Bradyrhizobium strains other than B. ]aponicum it was suggested that they be referred to as Bradyrhizobium sp. with the name of the host plant in parentheses immediately following [218], e.g., Bradyrhizobium sp. (Parasponia). d And further references therein. The older designation was used throughout this review.f Probably, this strain belongs to R. fredii [25]. In this review no differentiation is made between the almost isogenic strains Rhizobiurn sp. strain NGR234 and strain MPIK3030 [227].g See text for a recent dispute. 42tractant [48]. The nodulation genes are probably not involved in this chemotactic response [49].Chemotaxis towards nod gene-inducing flavonoids was also reported for Rhizobium leguminosarum strains [33,50]. In this case, the symbiotic plasmid, which carries all known nod genes, was beneficial, but not essential, for chemotaxis [50]. In contrast, none or only a very weak chemotaxis towards inducers of nod gene transcription was detected in B. japonicum [34,40]. Bj [243]; NGR234 [244]; Rlbt [245]; Rm [107] Bj [115,243]; Rlbt [98]; Rlbv [99]; Rm [47] Rlbv [99] Rm [102] Rlbv [99]; Rm [47] Rm [246] Rlbp [247] Rlbp [247] Rlbp [247] Ac [248]; Rlbt [98]; Rm [107] Ac [75]; NGR234 [244]; Rlbp [81,249]; Rlbv [99] Rlbv [250] Rlbv [99] Rlbv [250] Rlbp [249]; Rlbv [99] Rlbp [247] Rlbp [247] Rlbp [247] Rm [102] Bj [115,243,251]; NGR234 [244] Bj [115,243]; Rlbp [81.249] Bj [243] Bj [243] Bj [1151 Bj [243] Bj [85]; Rlbt [92]; Rlbv [92]; Rm [107] Only the most potent inducers are listed. Additional inducers are recorded in the literature cited. b Abbreviations for rhizobia: Ac, A. caulinodans; Bj, B. japonicurn; NGR234, Rhizobium sp. strain NGR234; Rlbp, R. legurninosarum by. phaseoli; Rlbt, R. leguminosarum bv. trifolii; Rlbv, R. leguminosarum bv. L,iciae; Rm, R. meliloti.