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  Section: General Biotechnology / Plant Biotechnology
 
 
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Biological Control of Plant Pathogens, Pests and Weeds

 
     
 

Historical Background

History of biological control of plant pathogens dates back to 1900s when Potter (1908) demonstrated the inhibition in activity of plant pathogens by an accumulation of its own metabolic compounds. Sanford (1926) suggested the control of potato scab by green manuring. He proposed two concepts for disease control (a) saprophytic microorganisms can control the activity of plant pathogens, and (b) the microbial balance of soil can be changed by altering the soil conditions.

Addition of fresh organic material will promote the activity and multiplication of saprophytes which by competition for nutrients and oxygen, and by their excretion will depress the activity and multiplication of the pathogens. Millard and Taylor (1927) also reported the control of scab of potatoes grown in sterilized soil inoculated with Streptomyces scabies through simultaneous inoculation of the soil with S. praecox, a vigorous saprophyte. Sanford and Broadfoot (1931) then provided an experimental evidence for Sanford's original hypothesis and demonstrated that infection of wheat seedlings by Ophiobolus graminis in sterilized soil could be completely suppressed by antagonistic action of various individually co-inoculated species of fungi and bacteria.

 

Weindling (1932) reported the parasitation by Trichoderma viride of many soil fungi. Control of rhizoctonia damping off of citrus seedlings has also been reported by Weindling and Emerson (1936).

 

Significance of antibiotic production by soil micro-organisms and their possible role in biological control by antibiosis and fungistasis have been discussed by Garrett (1956), Lingappa and Lockwood (1961); Jackson (1965), and Dwivedi and Saravanamuthu (1985).

 

In recent years, significant researches done on mycoparasitism, mycophagy, nematophagy and antibiosis have led to rapid development of training of antagonists to be applied in biological control of plant pathogens/disease in many ways (Cook, 1977; Old, 1977; Chakraborty et al, 1983; Elad et al, 1984; Manocha, 1985; Dwivedi, 1986).

 

Content

Biological control of plant pathogens 

 

Inoculum

 

Historical background

 

Phyllosphere-phylloplane and rhizosphere-rhizoplane regions

 

Antagonism

 

 

Amensalism (antibiosis and lysis)

 

 

Competition

 

 

Predation and parasit­ism : Mycoparasitism, nematophagy and mycophagy

 

Application of biological control

 

 

Crop rotation

 

 

Irrigation

 

 

Alteration of soil pH

 

 

Organic amendments

 

 

Soil treatment with selected chemicals

 

 

Introduction of antagonists : Seed inoculation, vegetative part inoculation and soil inoculation

 

 

Use of mycorrhizal fungi

 

Genetic engineering of biocontrol agents

Biological control of insect pests

 

Microbial pesticidies

 

 

Bacterial, viral and fungal pesticides

 

 

Viral pesticides

 

 

Mycopesticides

Biological control of weeds

 

Mycoherbicides

 

Insects as biocontrol agents


Table 13.1. Types of antagonists.

Bacteria

Actinomycetes

Fungi

Soil amoeba

 

 

1. Mycoparasites :

 

Aerobacter cloacae

Streptomyces sp.

Aspergillus

Arachnulla

Agrobacterium

radiobacter

Micromonospora globosa

Chaetomium

Arcella

Bacillus megaterium

 

Gliocladium

Gephyramoeba

B. subtilis

 

Penicillium

Geococcus

Bacterium globiformae

 

Pythium

Sccamoeba

 

 

Spicaria,

 

 

 

Talaromyces,

Vampyrella

 

 

Trichoderma

 

 

 

2. Nematophagous fungi

 

 

 

Arthrobotrys

 

 

 

Phialospora

 

 

 

Arthrobotrys

 

 

 

Phialospora

 


 
     
 
 
     



     
 
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