natural-products-in-plant-pest-management

264 S. Hettiarachinatural colourings, fragrances and microbial polysaccharides are becomingthe choice to replace artificial chemicals in the food and cosmetic industries.Several contemporary approaches have widened the usefulness of naturalcompounds. For example, a new move employing rhizosphere metabolamicsfor bioremediation of polychlorinated biphenyls is suggested (Narasimhanet al., 2003), where plants exuding high levels of phenylpropanoids haveenhanced rhizosphere populations capable of degrading pollutants.The study of the chemistry and extraction of natural products is soimportant that an entire discipline of chemistry is termed natural productchemistry. Many natural products have quite complex chemical structures,including stereochemistry, and hence their chemical synthesis is difficult. Yetsome simpler compounds of natural origin are made by total synthesis andthese are also treated as natural compounds. Scientists are also keen to elucidatethe biochemical pathways of natural product formation. This informationwill lead to the development of technologies for the overproduction ofalready existing natural products as well as producing entirely new productsthrough biological systems.Plants and animals have coexisted with their pests, pathogens,grazers/predators and other competitors throughout evolution. In order forthem to succeed in such a hostile atmosphere, coevolution has gifted theorganisms with defence mechanisms of different natures, chemical defencebeing one of them. Therefore living beings are natural factories of chemicalwarfare. Scientific investigations guided by traditional knowledge have led tothe identification of useful natural compounds for the benefit of humankindin medicine, veterinary medicine and in agriculture. Members of all classes ofliving beings from bacteria to higher plants and animals have been identifiedas sources of natural products. According to the accepted definitions of biotechnology,exploiting these organisms either from the wild or by cultivationfor the production and extraction of products comes under biotechnology.This exploitation has already threatened some valuable plants and animalswith local or even global extinction due to over-exploitation, for example formedicinal uses (Kala, 2005; Maundu et al., 2006). The use of new biotechnologicaltools would certainly ease the pressure on natural populations.Although biotechnology plays an important role in non-biologicalnatural products, these are not included in this discussion.13.2 Biotechnology in Genetic Diversity Revelation andConservationIt is well known that different varieties / races of the same species have differentchemical properties and hence their level of importance as sources ofnatural products may be different. Until recent times, the taxonomy andidentification of plants, animals and microorganisms were based on morphological(vegetative and reproductive) and anatomical characters. However,these features usually cannot differentiate between two closely relatedindividuals and hence cannot identify those individuals with the same