Morphological, Physiological and Molecular Markers for the Development of Resistance in Cotton against Insect Pests

Cotton is a very important fiber and oilseed crop of many countries. The economy of most countries is dependent upon it. Both abiotic and biotic factors affect the crop yield and quality. In the biotic factors, sucking and chewing insect pests (white fly, jassids, pink bollworm, spotted bollworm and army bollworm) affect cotton crops drastically at early and reproductive stages. The farmer is always using chemical control method to control all these pests which increases the cost of production to many folds. In addition to this it also causes many environmental as well as health hazards. In-built resistance in plants is offered by various mechanisms that can be of morphological, physiological and molecular origin; these mechanisms can be exploited for the purpose of ameliorating the current scenario. The use of morphological, physiological and molecular markers for the ideotype plant development is regarded to be useful and practical. Morphological markers can be used by visual observation, e.g. leaf shape, color, structure, trichomes, and number of gossypol glands and amount of waxes etc. These can be used widely and with great ease. Physiological markers used at the protein level evaluate its expression in cotton against insects. The plant produces a special group of proteins as lecitins and other phenolic compounds that reduce the insect population to a great extent. Molecular markers used at the genetic level may evaluate the presence of genes that are involved in producing structures and chemicals to prevent the invasion of foreign pests. These have the ability to express and play important role in cotton against insect pests. Genes of interest can be transferred by genetic engineering in recommended varieties. This review paper covers the morphological, physiological and molecular markers associated with resistance development against insect pests in cotton.