In traditional plant breeding, new varieties are developed either by selecting plants with desirable characteristics or by combining qualities from two closely related plants through selective breeding. These features may for example be resistance to a particular pest or disease, or tolerance to climatic conditions. Pollen with the genes for a desired trait is transferred from plants of one crop variety to the flowers of another variety with other desirable traits. Eventually, through careful selection of offspring, the desired trait will appear in a new variety of plants. Traditional plant breeding has produced numerous highly successful new varieties of crops over the centuries