Role of micronutrient in the suppression of root knot nematode,Meloidogyne javanica by Pseudomonas fluorescens strains CHA0 and itsGM derivatives
2004
Siddiqui, I.A. | Shaukat, S.S. | Hamid, M.,Karachi Univ. (Pakistan).Dept. of Botany
Under laboratory conditions, the growth and nematicidal activityof the biocontrol strain Pseudomonas fluorescens strain CHA0 and itsgenetically modified derivatives were tested by the amendment ofdifferent mineral elements. In general, nutrient yeast extract brothsupplemented with microelements had no significant impact on thegrowth of biocontrol bacterial inoculants compared to the unamendedcontrols. Of the minerals tested, KmnO4 drastically inhibited bacterialgrowth while MnCl2 enhanced bacterial populations. Regardless of thebacterial inoculants, microelements did not substantially influence thepH of the growth medium. Culture filtrates (CF) of the bacteriaresulting from nutrient yeast extract broth (NYB) amended withmolybdenum (Mo) or zinc (Zn) markedly enhanced the nematicidalactivity of both CHA0 and CHA0/pME3424 while MgSO4 and MgCl2exhibited lowest nematicidal activity. When the three bacteria werecompared for the nematicidal activity, CF of strain CHA0/pME3424caused highest mortality of M. javanica juveniles, while strain CHA89failed to produce such effects. Efficacy of the biocontrol agentsagainst M. javanica was evaluated in the repeated experimentsconducted in sandy-loam soils under glasshouse conditions. Biocontrolinoculants significantly reduced nematode population densities andsubsequent root-knot infection in two different legumes i.e. mungbeanand soybean. The biocontrol activity of the two strains varied withthe host plant.
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