January 2005          The CRS CommPoster     7

 

 

 

Yes. We do Have a Choice:                      

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diseases: Use of microorganisms for control of microbial diseases: In early 1930s, Scientists at Aberdeen  (Dr. Alan Paton and his associates) demonstrated the use of L phase bacteria for controlling bacterial diseases in crop plants.   L phase bacteria are naked bacteria. By treating bacteria with lysozyme (enzyme), researcher destroys the outer wall of bacteria.  Plants inoculated with L phase bacteria, Pseudomonas spp. do not develop microbial diseases.  

 

Recently, a novel bacterial biocontrol agent, Pseudomonas fluoroscens has become quite popular in the control of fungal diseases of crop plants.  Soil borne  Pseudomonas fluoroscens can check soil-borne and leaf diseases.  This microbe has the unique ability to control diseases as well as promote plant growth.   It colonizes the root cells,  enters the plant vascular streams, reaches the leaves and acts as a systemic bio-control agent against diseases.

 

The bacterium produces antibiotics such as pyoluteorin, pyocyanin and phenazine, which inhibit the growth of fungal pathogens. Pseudomonas fluorescens readily controls disease causing organisms such as Pythium, Rhizoctonia, Fusarium, Pyricularia, Helminthosporium and bacterial pathogens such as Eriwinia and Xanthomonas.

 

It also produces chemicals that chelate with iron in the soil, and make it difficult for the pathogens to proliferate. It interferes with the germination of fungal spores and their growth mechanism thus preventing its establishment on the crops. By secreting an enzyme, it can dissolve the cell walls of several fungal pathogens and thus annihilate them.

 

    Pseudomonas fluoroscens secretes several plant growth substances, and these gibberellin-like compounds contribute to vigorous crop growth. This bacterial agent is compatible with the antagonistic fungus, Trichoderma viride and other species as well. In combination with other

 

 

fungal bio-control agents, one can use Pseudomonas to control a wide variety of plant diseases.

 

The bacterial agent can be used for treating seeds for pathogen resistance.  Dip roots of seedlings prior to transplantation. The bacterial suspension can be sprayed on the leaves to contain leaf diseases. When applied in the soil, the bacteria move towards plant roots and grow profusely over the root surface. It, then,  enters the vascular tissue to act as a systemic agent.  Chemical exudates by pathogenic organisms attract Pseudomonas.  The bacterium using its flagella moves fast towards the target pathogens.  The root exudates from the plants also attract the bacteria. Bacteria grow over the root surface. The bacterium, then, acts as a shield against the invading plant pathogens

 

You can also apply the bacteria with other biofertilizers such as Bacillus megatherium. Because of its compatibility with a wide range of bio-fertilizers and bio- control agents, it is an ideal candidate for integrated pest management programs.

 

     For treating the seeds, use about a gram of the bacterial culture for mixing with a kg of seeds.  When you grow roses from seeds, dip seedlings in 0.5 per cent suspension for roughly two hours.   For soil application, mix 2.5 kg of the culture with sand and spread over a hectare. As a plant protection spray, use 0.5 percent suspension.

 

This biocontrol agent is systemic, and establishes itself within plants in no time.  Repeated applications, therefore, are not necessary.  It should make life easy for rosarians. Pseudomonas fluorescens is not a human pathogen.

 

Bacillus leptosporus, another soil borne bacterium is commercially available as ‘Rosa

 

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