Introductory principles

Ever since growers first selected seed for their next crop, they have influenced the genetic make-up and potential of succeeding crops. A basic understanding of plant breeding principles is useful if horticulturists are to understand the potential and limits of what plant cultivars can achieve, and so that they can make realistic requests to the plant breeder for improved cultivars. Plant breeding now supplies a wide range of plant types to meet growers’ specific needs. The plant breeder’s skill relies on their knowledge of flower biology, cell biology and genetics. Desirable plant characters such as yield, flower colour and disease resistance are selected and incorporated by a variety of methods. This chapter attempts to give a background to the principles used by plant breeders.

Plant breeding follows two scientific findings. Firstly, characteristics of a species are commonly passed on from one generation to the next (heredity). Secondly, sexual reproduction is also able to generate different characteristics in the offspring (variation) . A plant breeder relies on the principles of heredity to retain desirable characteristics in a breeding programme, while new characteristics are introduced in several ways to produce new cultivars.

The processes of pollination and fertilization are first discussed as they are the plant processes that lead to the genetic make-up of the plant that follows.