Pathogenic microorganism or their products (toxin and plant used as suppress the insect population is called Biopesticides.
The concept of Biopesticides is by no means new. Over a country ago, introduced in India to fight foreign cactus and by 1938 the first Bt product had appeared in the market. Research on Biopesticides involves the isolation of naturally occurring strains of organism and the determination of their target specificity.
The possibilities of micro-organism used in insect pest control are shown in following table:
i) Bacillus popilliae, ii) Bacillus thuringiensis.
i) Japanese beetle,ii) Mosquitoes and Lepidopterous pests.
Lepidoptera, mustard saw fly orthoptera, mosquito, mites
i) Beauveria bassiana , Aspergilus flavus,Metarhizium anisopliae,ii) ferticulium
i) Homoptera, Lepidoptera, Coleoptera, Hymenoptera,Diptera.ii) Aphids, whitflies.
The most widely used bacterium Bacillus thuringiensis (Bt) produces a toxic crystalline protein which when fed to susceptible insects, dissolves in the guts, damaging and eventually killing the insect. However, Bt based insecticides have some draw backs. The toxin usually have short self-life and remain effective for short periods because the toxic protein is broken down by sunlight and other climatic factor. Another limitation has been the much higher cost of Bt pesticides.
Selected Commercial Microbial Insecticides:
Sandoz India Ltd. has started a Bacillus thuringiensis based pesticide in 1992. The product is delivered in water dissolvable microorganules form under the brand name Delfin. It is active against caterpillars which attack cabbage and cauliflower.
Hindustan Liver Ltd. have also produced a bio insecticides based on Bacillus thuringiensis using molasses as culture medium. It is found useful against the insect attacking cabbage, pigeon pea, cotton, safflower and maize as well as against black flies and mosquitoes.
Attempts are under way to effectively manage insect resistance by placing Bt toxin genes of several stains into the plants. The increasing availability of diverse Bt toxin may conceivably allow for management of pest resistance. By using gene transfer technique transgenic plants in maize and cotton have been developed by introducing Bt gene in these crops.
There are many microorganism which attack insects. These microscope are called entomopahtogens. Entomopahtogens include many viruses, bacteria, fungi, and protozoa. Many arthropod pests are susceptible to viral diseases of the various kinds of insect viruses, two, viz, nucleopolyhedrosis viruses ( NPV) and granulosis viruses ( GV) have shown considerable promise as insect control agents in view of their specificity, safety, virulence and stability. Some of the host insect that may be controlled by these viruses include almond moth, Asiatic rice borer, bolloworm, cotton, leaf-down, cabbage loper, corn earworm, gypsy moth and codling moth, potato tuberworm, spruce budworm and Asiatic rice borer ( all through GV).
Germplasm may be defined as the irreplaceable genetic building material from which essential plant product can be derived.
Proper germplasm storage is basic to the development of plant biotechnology that has valuable applications in agriculture and industry. The range of in vitro germplasm conservation systems involved in plant biochemistry extends from the non-cellular through protoplasts, cells and tissues to highly organised cultures such as shoot tips and plantlets. Some technique involve storage in the growing stage whereas other relate to the suspension of growth. Growth limitation ( E.g. By temperature reduction, use of retardant chemicals or hormones, and reduction in oxygene concentration) typically remains effective for cultures to be stored for about a year, and such cultures require periodic renewal. The another method is cryopreservation which often can store materials for virtually indefinite period.
Methods of Conservation:
1. In- situ Conservation:
This method of conservation mainly aims at preservation of land races with wild relatives in which genetic diversity exists or in which the weedy or wild forms present hybridise with related cultivars. These are evolutionary systems that are difficult for plant breeders to stimulate. The in-situ conservation of habitats has received high priority in the world conservation strategy programmes launched since 1980.
2. Ex-situ Conservation:
Ex-situ conservation is the chief mode of preservation of genetic resources, which may include both cultivated and wild material. Generally, seeds or in vitro maintained plant cells, tissues and organs are preserved under appropriate conditions for long term storage as gene banks.