Suppression of Meloidogyne incognita by Pseudomonas fluorescence strain CHA0 and its genetically modified derivatives: I. The influence of oxygen

I. A. Siddiqui, S. S. Shaukat, M. Hamid

Abstract


Culture filtrates of the biocontrol strain Pseudomonas /luorescens CHAO and its genetically modified, antibiotic overproducing strain CHAO/pME3424 and antibiotic-deficient strain CHA89 caused substantial mortality of Meloidogyne incognita juveniles in vitro. The bacterial inoculants incubated in limited oxygen conditions caused greater juvenile mortality compared to the culture filtrate obtained from medium kept at ambient oxygen conditions. Strain CHAO/pME3424 caused greater juvenile mortality compared to CHAO or CHA89 regardless of the incubation conditions. Under glasshouse conditions, the bacterial inoculants used as a soil drench caused marked reduction in nematode population densities in tomato roots compared to the controls. The three bacteria applied separately in the soil watered from the top caused greater reduction in nematode populations compared to the pots watered from the bottom. Regardless of watering, the greatest reduction in nematode populations was achieved after soil treatment with strain CHAO-pME3424. The bacterial antagonists applied in the soil watered from the top enhanced plant growth and protein contents of the leaf. The three bacterial inoculants did not differ significantly in their colonization pattern regardless of watering method. However, the bacterial populations were significantly (p<O.05) higher in the pots watered from the top.

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