Genetic Engineering is the deliberate, controlled manipulation of the genes in an organism with the intent of making that organism better in some way. This is usually done independently of the natural reproductive process .The result is a so-called Genetically Modified Organism (GMO). To date, most of the effort in genetics engineering has been focused on agriculture. An elaborate discussion on inbreeding depression, hybrid vigour, hybrid varieties, resistance of plants to fungal diseases and pests, breeding resistant varieties, polyploidy as well as mutation in plant breeding, and distant hybridization for plant improvement also finds place in the book. It is useful for post-graduate students of agriculture and horticulture.