Screening for Effective Biocontrol Agents on Phytopathogens Like Agrobacterium and Fusarium

Numerous techniques have been devised to prevent bacterial contamination and spread of disease. there are many methods used against bacterial diseases, bacteria are usually very difficult to control. Frequently, a combination of several control measures is required to combat a given bacterial disease. Soil infested with plant pathogenic bacteria can be sterilized with steam or dry heat, or with certain chemicals.

The terms “biological control” and its abbreviated synonym “biocontrol” have been used in different fields of biology, most notably entomology and plant pathology. In entomology, it has been used to describe the use of live predatory insects, entomopathogenic nematodes, or microbial pathogens to suppress populations of different pest insects. In plant pathology, the term applies to the use of microbial antagonists to suppress diseases as well as the use of host-specific pathogens to control weed populations. In both fields, the organism that suppresses the pest or pathogen is referred to as the biological control agent (BCA). More broadly, the term biological control also has been applied to the use of the natural products extracted or fermented from various sources. These formulations may be very simple mixtures of natural ingredients with specific activities or complex mixtures with multiple effects on the host as well as the target pest or pathogen.

National Research Council took into account modern biotechnological developments and referred to biological control as “the use of natural or modified organisms, genes, or gene products, to reduce the effects of undesirable organisms and to favor desirable organisms such as crops, beneficial insects, and microorganisms”, but this definition spurred much subsequent debate and it was frequently considered too broad by many scientists who worked in the field (US Congress, 1995). Because the term biological control can refer to a spectrum of ideas, it is important to stipulate the breadth of the term when it is applied to the review of any particular work.

Most broadly, biological control is the suppression of damaging activities of one organism by one or more other organisms, often referred to as natural enemies. With regards to plant diseases, suppression can be accomplished in many ways. More narrowly, biological control refers to the purposeful utilization of introduced or resident living organisms, other than disease resistant host plants, to suppress the activities and populations of one or more plant pathogens. This may involve the use of microbial inoculants to suppress a single type or class of plant diseases. Or, this may involve managing soils to promote the combined activities of native soil- and plant-associated organisms that contribute to general suppression. Most narrowly, biological control refers to the suppression of a single pathogen (or pest), by a single antagonist, in a single cropping system.

Apart from these antagonists, plant extracts can also be used for the control of various plant pathogens. Studies have shown that the extraction method of medicinal plants have profound effect on various phytopathogens. Most of the phytopathogen which shows resistance against various bacterial strains as well as chemical agents are generally treated with such medicinal plant extracts. This approach has shown great importance as well as effectiveness in cases such as infection due to various fungal and bacterial pathogens. The plant extractes can be directly used against the pathogen as well as can be used in combination with phenol as well as various antimicrobial substances to which most of the pathogens are sensitive. This approach provides an easy way of treating diseased plants as this is an efficient as well cost effective way.