Use of molecular biology techniques for the management of insect pests
1. Wide hybridization: This method entails conventional breeding to transfer genes from one species to another. Resistance genes are transmitted from a different species. For example, the WBPH resistance gene has been transferred from Oryza officinalis to Oryza sativa.
2. Somaclonal variability:-. Variation in tissue culture generated offspring, such as somaclonal sorghum varieties resistant to Spodoptera litura, has emerged.
3. Transgenic plants: — Transgenic plants are those that have one or more extra genes. This is accomplished by the use of genetic engineering methods to clone new genes into the plant genome. Pest resistance is conferred by the additional genes.
Transgenic Bt plants Target insect pests
1. Cotton– Bollworms, S. litura
2. Maize– European corn borer
3. Rice–Leaf folder, stem borer
4. Tobacco, Tomato– Cut worms
5. Potato, Egg plant–Colarado potato beetle
The insertion of one or more of the following genes resulted in transgenic plants:
a. Bt endotoxin from Bacillus thuringiensis
b. Protease inhibitors
c. -Amylase inhibitors
a. Bt endotoxin gene:
(delta) endotoxin is a crystal toxin produced by the gram-positive bacterium Bacillus thuringiensis.
When ingested, the endotoxin is a gastrointestinal poison that kills the lepidopteran insects.
To make Transgenic cotton, the gene (DNA fragment) responsible for creating endotoxin is extracted from Bt and cloned into plants such as cotton, potato, maize, and so on.
b. Protease inhibitors (PI) gene
Insects’ guts contain proteases, which are enzymes that aid in protein digestion. Insect digestion is affected by protease inhibitors, which are chemicals that block proteases.
To create transgenic plants, the protease inhibitor gene is extracted from one plant and cloned into another.
E.g- transgenic apple, rice, and tobacco with PI. CpTI is a trypsin inhibitor obtained from cowpea and cloned into tobacco. Heliothis virescens is resistant to this transgenic tobacco.
c. -Amylase inhibitor gene
-Amylase is a carbohydrate-digesting digestive enzyme found in insects. – Amylase inhibitors impact insect digestion.
Tobacco and tomato transgenics expressing -amylase inhibitor have been developed, making them resistant to Lepidopteran pests.
d. Lectins genes
Lectins are carbohydrates-binding proteins. When insects consume lectins, they attach to chitin in the peritrophic membrane of the midgut, preventing nutrients from being absorbed. e.g.
H. virescens is resistant to transgenic tobacco expressing the pea lectin gene.
e. Enzyme genes
Plants have been cloned with the chitinase enzyme gene and the cholesterol oxidase gene, both of which have insecticidal capabilities.
Pyramiding of genes is the process of engineering transgenic crops using many genes to achieve multimechanistic resistance. e.g.
1. To create a tranagenic tobacco, the CpTi gene and the pea lectin gene were cloned.
2. Potato transgenics expressing lectin and bean chitinase have been developed.
Potentials/Advantages of Biotechnology in IPM
1. Resistance to transgenic Bt, PI, and lectins develops slowly.
2. Because poison is expressed in all sections of the plant, there is no need to apply insecticides.
3. There is no requirement for constant monitoring.
4. There is no pollution in the environment, it is safe for the NE, and it is not a target organism.
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