Bacterial antagonists to the take-all fungus and fluorescent pseudomonads in the rhizosphere of wheat

The numbers of antagonists to the take-all fungus, and of fluorescent pseudomonads were significantly different in the rhizosphere and “residue” of seminal and nodal wheat roots of similar age.The rhizosphere of 1 week-old and the residues of 3 and 5 week-old nodal roots harboured significantly more antagonists than seminal roots. The rhizosphere of 5 week-old seminal roots, however, supported more antagonists than that of nodal roots of similar age. Combined analysis of all sampling stages showed that the nodal roots exerted a significantly greater “rhizosphere effect” on antagonists than the seminals.Fluorescent pseudomonads in the rhizosphere of 1, 3 and 8 week-old seminal roots were present in significantly higher numbers than in nodal roots of similar age. The combined analysis of all stages showed that the rhizosphere of seminal roots supports a significantly larger population of fluorescent pseudomonads.The implication of these differences is discussed in relation to the ecology of the take-all fungus.