Inhibition of fungi from wheat roots by Pseudomonas fluorescens 2–79 and fungicides

Nine commercial fungicides and two antibiotics from Pseudomonas fluorescens 2–79 were tested using 22 fungal species that are frequently found on diseased cereal roots. On agar plates, bitertanol (one of the nine fungicides tested) inhibited the growth of 20 22 fungi; whereas metalaxyl inhibited 5 21 fungi. Of the antibiotics, phenazine-1-carboxylic acid inhibited 17 22 fungi, but the siderophore was not inhibitory. Bitertanol or metalaxyl was added to three soils, naturally infested with Gaeumannomyces graminis var. tritici(Ggt). Pseudomonas fluorescens 2–79 was added to fungicide treated and to untreated soils. Wheat was then grown in these soils for 3 weeks. A range of fungi was isolated from the wheat roots. P. fluorescens 2–79 reduced the numbers of Rhizopus spp. isolated and in one soil improved wheat germination. In one soil bitertanol increased the shoot weight and reduced the numbers of Ggt and Fusarium spp. isolated. Bitertanol also increased the concentration of ammonium-N in the soils.