Genetic diversity plays an important role in crop evolution. Assessing diversity by morphometric through classical plant breeding is very much useful to study the crop evolution and to identify suitable parents for developing superior progenies. The genetically diverse parents will show high combining ability resulting in high heterosis in F1 generation and throw some useful segregants in the F2 and in later segregating generations too. Genetic diversity has been classically measured with Mahalanobis’ D2 method. Diversity analysis over season and environments also gives useful information in identification of suitable parents. The consistent genetic diversity over seasons and environments would be useful in practical plant breeding. Further, genetic diversity has also being measured with molecular markers to avoid environmental interaction. The book carries useful information on genetic diversity and phenotypic stability among various field and horticultural crops for the researches who involved in crop improvement program.