Phenotype versus Genotype (FENOTIF Versus GENOTIF)
An important term used throughout this book is phenotype, which simply means “what something looks like.” We often speak about the phenotype of a specific trait, in which case it takes on units of measurement. For example, the phenotype of a quantitative trait such as seed weight in wheat might range between 30 and 80 mg. The term phenotype is also used to distinguish what a plant looks like from its genotype (what genes are present) or genotypic value (what we would expect the phenotype to be if we could predict it exactly from the genotype). A fundamental concept in plant breeding is that genotypic value is something that we try to measure and predict. If we could identify or control all the unpredictable effects of error and environment, then the phenotype of a plant (P) would be equal to its genotype (G) plus the effects caused by error and environment (E). Virtually all of the fancy equations that you will see in plant breeding books are derivations of this basic formula. ...