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| Analysis of Colonization Ability of Six Biocontrol Bacteria in Cucumber Plants under Chemical Stress Condition |
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| DOI：10.16768/j.issn.1004-874X.2022.02.015 |
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| Abstract: |
| 【Objective】The study was carried out to explore the effect of chemical stress on the colonization ability of
biocontrol bacteria on cucumber plants.【Method】By setting a greenhouse experiment and two field experiments, biocontrol
bacteria were inoculated on cucumber plants without fungicides and pathogens, with fungicides and without pathogens, with fungicides and pathogens, respectively.【Result】The six biocontrol strains tested had good colonization effects on cucumber
leaves and roots. Under the greenhouse conditions without fungicides and pathogens, the colonization of each biocontrol strain
showed a trend of decrease-increase-stability, strains 1BS4 and 3BY4 had strong colonization ability in cucumber leaves and
roots. The colonization quantity of strains 1BS4 and 3BY4 was close to 106
CFU/g(FW) at 30 days post inoculation(dpi) about 104
CFU/g(FW); Under the field conditions without fungicides and with pathogens, there were significant differences in the colonization
quantities of various biocontrol strains in leaves and roots, and they all showed a trend of decrease-increase-decrease-stability.
Strain 5BJN1 had the strongest colonization ability. The colonization quantity of cucumber leaves and roots at 30 dpi was 105.92
CFU/g(FW) and 104.95 CFU/g(FW), respectively; Under the field conditions with both fungicides and pathogens, there were
differences in the colonization quantity of biocontrol bacteria in leaves and roots, but the difference was not significant, and all
showed a trend of decrease-increase-decrease-stability, and the colonization quantities of strains 3BJN7 and 5BJN1 in cucumber
leaves at 30 dpi were relatively high, which were 103.88 CFU/g(FW) and 104.23 CFU/g(FW), respectively. The colonization quantity
of other strains was about 103
CFU/g(FW).【Conclusion】The effect of chemicals on the colonization ability of biocontrol bacteria
depends on the types of strains. Some strains (3BJN7 and 5BJN1) have good compatibility with chemicals. In the presence of
cucumber downy mildew, they can still maintain a certain amount of colonization after using chemicals, therefore, they can be
used as potential biocontrol agents; In the absence of fungicide stress, the emergence of downy mildew pathogen can induce the
improvement of colonization ability of strain 3BJN7 so that it can colonize stably on cucumber plants. |
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