This fourth book in the Plant Breeding Series introduces the techniques required to analyse the quantitative genetical variation confronting all plant breeders. It clearly describes the methods available to handle complex characters and their responses to the stresses and constraints imposed on them by the environment. The book focuses on ecological aspects related to breeding, in particular the role of the genetic conservation and gene banks, in supplying plant breeders with the genetically variable material required to produce new varieties of the crop plants. Integrating scientifically both the quantitative and conservational aspects of plant breeding, this important volume will be of interest to students pursuing courses in applied genetics as well as providing an invaluable source for those working in the field to tackle the problems facing plant breeders in the 21st Century.