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Banaras Hindu University (2015)

Development of transgenic cotton Gossypium hirsutum L expressing a novel chitinase for the control of whitefly Bemisia tabaci

Shukla, Anoop Kumar

Titre : Development of transgenic cotton Gossypium hirsutum L expressing a novel chitinase for the control of whitefly Bemisia tabaci

Auteur : Shukla, Anoop Kumar

Université de soutenance : Banaras Hindu University

Grade : Doctor of Philosophy (PhD) 2015

Résumé
Most of the present agricultural crops are developed through breeding to maximize yield. These breeding programs lack ability to transfer resistance across genera or kingdoms. Genetic engineering offers a platform to transfer genes among less related genera and even from distant kingdoms. Biotechnology has now brought transgenic crops which have foreign genes providing resistance against biotic and abiotic stresses. Among the biotic stresses, insects alone cause 15-80% loss of the crop yield in field with an average loss to the farmers of about 24.7%. A total 1326 insect species infest the crops worldwide.

Cotton crop is attacked by more than 200 insect pests. These insects are primarily of two types : (i) biting and chewing type lepidopteran insects such as fruit borer (Helicoverpa armigera), tobacco cutworm (Spodoptera litura), diamondback moth (Plutella xylostella), pink boll worm (Pectinophora gossypialla), and (ii) piercing and sap sucking type hemipteran insects such as aphids (Aphis gossypii), whiteflies (Bemisia tabaci), jassids (Amrasca biguttula biguttula), thrips (Thrips tabaci L.), mealybugs (Phenacoccus hirsutus). The problem of chewing pest predation has been addressed with help of genetic engineering where chimera of cry genes were introduced in cotton and expressed constitutively. The genetically modified cotton (also known as Bt-cotton) has shown effective resistance against lepidopteran pests and is commercially cultivated since 1996 worldwide. The affectivity of Bt-technology is also exploited in commercially grown soybean, maize and canola. Bt-toxins were specific to chewing pest and was not effective on sap sucking pests like white fly, aphid, jassids mealybugs. With the adoption of Bt-cotton by farmers, insecticide spray was minimized, that in turn resulted in serious outbreak of sap-sucking insects.

Biotechnological approaches to combat sap sucking pest were unsuccessful. Till date several natural anti-insect molecules have been identified against this sap sucking pest. These includes proteins like snowdrop lectin, GNA, α-amylase inhibitors, Allium sativum lectins, Photorhabdus luminiscences isolated insecticidal protein, cholesterol oxidase and avidin which were deployed for genetic engineering of plants for the insect resistance. Recently, transgenic plant mediated RNA interference has been demonstrated to control both types of insects. Genetic engineering of plants including cotton with these proteins and si-RNA has been reported to be promising in various laboratories. The failure might be due to low and non-exclusive toxicity of these molecules, used against whitefly.

Présentation et version intégrale (Shodhganga)

Page publiée le 5 février 2021