It gives me an immense debt of gratitude to express my sincere thanks to my supervisor Dr. Vanga Siva Reddy, for his excellent guidance, constant encouragement, patience and care during the entire course of Ph.D. I fell very fortunate to have an opportunity work under his patient supervisor.

I am thankful to Prof. A. Falaschi, Director ICGEB, Trieste, Italy; Prof . V.S Chauhan, Director ICGEB, New Delhi; Mrs H.S. Narayanan, ICGEB chief administrative officer for providing me an opportunity to carry out my research at ICGEB.

I am especially thankful to Dr. Sadhu Leelavathi, I can say she is my co-supervisor with high respect and deep sense of appreciation for her expert and active involvement in each, experiment explaining clearly, providing all necessary things to carry out research at Plant Transformation group ICGEB. Specifically, I wish to acknowledge her preliminary correction of my thesis.

I am sincerely thankful to Prof. S.K. Sopory, Dr. Raj Bhatnagar and all the scientists, who has helped me during my Ph.D. work.

I am very much thankful to all the members Insect Resistance and all the groups of Plant Molecular Biology laboratory for their help and co-operation.

I am thankful to Dr. S. Jameel, Dr. V. Kumar, Dr. K.V.S. Rao, Dr. N. Khanna, Dr. S. K. Sopory, Dr. R. K. Bhatnagar, Dr. M. Mohan, Dr. S.K. Mukherjee, Dr. M.K.Reddy, Dr.N. Tuteja, Dr. C. Chitnis, Dr. A. Ranganathan and Dr. S. Swaminathan for taught me in Ph.D lecture courses.

I would like to thank Dr. Ratna, Dr. Sunny, Dr. Archana, Dr. Dolendro, Dr. Anju, Dr. Soumen, Dr. Das, Aparna,Vijay Kanth, Amit, Sachin and Dipa. Their presence and vital help made research my easy and enjoyable.

I deeply appreciate and acknowledge to Prof. Nguyen Van Uyen, Prof. Nguyen Tien Thang and Dr. Nguyen Huu Ho, Institute of Tropical Biology , Vietnam approving me four years study leave to conduct my Ph.D. in ICGEB, India .

I would like to thank my schoolmates, Wricha, Vineetha, Punjab , Dasaradhi, Suman, Sidharth, Chamari and Hung for their help in various ways.

I also wish to thanks Tina, Rekha, Radha, Ramesh, Sovan, Gita, Pratibha, Madan, Ashok, Richa and Ranaji for their assistance.

I am also thankful to Prakashji, Rajender and Ramesh for their cooperation.

Above and beyond all, my heartfelt gratitude to my parents, brothers and sister for their much needed support, patience, understanding, and encouragement in every possible way. And also my indebtedness towards my wife and my son, Phu, they have given me more than I can say. Their endless love, priceless, perpetual, indispensable help, support and everything made all this possible.

Nguyen Huu Tam