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BCAs AND SUPPRESSIVE SOILS.pptx

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DAMUS MWANGI

Fungi and bacteria are considered the most effective biological control agents against nematodes. They act directly through antagonism of plant-parasitic nematodes or indirectly by producing compounds that promote plant growth or induce resistance. Common fungal control agents include Trichoderma, Catenaria, and Aspergillus which repel or kill nematodes through various mechanisms. Bacterial control agents like Pseudomonas, Agrobacteria, and Pasteuria also antagonize nematodes through toxins, antibiotics, or by attaching and restricting movement. Nematode suppressive soils naturally limit nematode populations through parasitism and antibiosis from biological control agents, though soil properties and plant species can influence the level of suppression

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BIOLOGICAL CONTROL AGENTS AGAINST NEMATODES AND NEMATODE SUPRESSIVE SOILS
2. Biological control agents(BCAs) 2.1 Their General Categorization And Effect Fungi and bacteria currently considered the most effective BCAs Others BCAs like viruses and predaceous mites are less effective Challenges in testing BCAs benefits: Mass culture, formulation, application method and interaction with seed and media Their mode of action is ether directly or indirectly Direct antagonism against the PPNs or indirectly promoting hormones BCAs and their metabolites are responsible for PPN management
2.1 Their General Categorization And Effect Mechanism of BCAs action against PPNs: i. Produce plant growth promotors ii. Produce active compounds ang growth hormones iii. Produce lytic enzymes and antibiotics to suppress pathogens iv. BCAs can prime for PPN resistance v. Interact with roots to prime plants against RKN infection vi. Trap nematodes vii. Are parasite of nematode at all stages
Fungal control Fungal BCAs include: Trichoderma, Catenaria, Aspergillus and Pochonia Endophytic nematodes colonize roots and enhance plant defense They repel the juveniles stage 2 away from roots Retard PPN development Lower PPNs fecundity Trichoderma spp. kill RKN in the root system Pochonia induce resistance against M. incognita They also target cyst nematode Globodera spp.
Bacterial control Bacterial species of genera Pseudomonas, Agrobacteria, Rhizobium, Arthrobacter and Pasteuria control PPNs Their mode of actions are antagonism, antibiotic production and induced resistance B. thuringesis produces toxic particles of cry protein while B cereus raise secretion of repellent substances Pasteuria spp. Spores attach to surface of the nematode. The germ tube grows into the nematodes body The spores restrict nematode movement and the female produces few or no eggs Their endospore is resistant to drying, heat and shearing hence a good biocontrol
Nematode suppressive soils They are soils in which pathogens can not persist or cause disease Biological activity of such soils is shown when its suppressiveness is removed by biocides, reduce multiplication of nematodes and is heat sensitive Parasitism and antibiosis by BCAs were suggested in repressive soils Soil suppression acts against certain PPN species Soil properties and plant species influenced level of suppression Plant genotype control magnitude of BCA induced resistance Soil sterilization affects PPN and other biological organisms

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BCAs AND SUPPRESSIVE SOILS.pptx

  • 1. BIOLOGICAL CONTROL AGENTS AGAINST NEMATODES AND NEMATODE SUPRESSIVE SOILS
  • 2. 2. Biological control agents(BCAs) 2.1 Their General Categorization And Effect Fungi and bacteria currently considered the most effective BCAs Others BCAs like viruses and predaceous mites are less effective Challenges in testing BCAs benefits: Mass culture, formulation, application method and interaction with seed and media Their mode of action is ether directly or indirectly Direct antagonism against the PPNs or indirectly promoting hormones BCAs and their metabolites are responsible for PPN management
  • 3. 2.1 Their General Categorization And Effect Mechanism of BCAs action against PPNs: i. Produce plant growth promotors ii. Produce active compounds ang growth hormones iii. Produce lytic enzymes and antibiotics to suppress pathogens iv. BCAs can prime for PPN resistance v. Interact with roots to prime plants against RKN infection vi. Trap nematodes vii. Are parasite of nematode at all stages
  • 4. Fungal control Fungal BCAs include: Trichoderma, Catenaria, Aspergillus and Pochonia Endophytic nematodes colonize roots and enhance plant defense They repel the juveniles stage 2 away from roots Retard PPN development Lower PPNs fecundity Trichoderma spp. kill RKN in the root system Pochonia induce resistance against M. incognita They also target cyst nematode Globodera spp.
  • 5. Bacterial control Bacterial species of genera Pseudomonas, Agrobacteria, Rhizobium, Arthrobacter and Pasteuria control PPNs Their mode of actions are antagonism, antibiotic production and induced resistance B. thuringesis produces toxic particles of cry protein while B cereus raise secretion of repellent substances Pasteuria spp. Spores attach to surface of the nematode. The germ tube grows into the nematodes body The spores restrict nematode movement and the female produces few or no eggs Their endospore is resistant to drying, heat and shearing hence a good biocontrol
  • 6. Nematode suppressive soils They are soils in which pathogens can not persist or cause disease Biological activity of such soils is shown when its suppressiveness is removed by biocides, reduce multiplication of nematodes and is heat sensitive Parasitism and antibiosis by BCAs were suggested in repressive soils Soil suppression acts against certain PPN species Soil properties and plant species influenced level of suppression Plant genotype control magnitude of BCA induced resistance Soil sterilization affects PPN and other biological organisms