Читать книгу Principles of Plant Genetics and Breeding - George Acquaah - Страница 331

Some crops rely on clonal propagation: tubers, corms, cuttings, bulbs, stolons, etc. Such crop species may have lost the capacity to flower (leek, some potato cultivars). Their progeny is genetically identical to the plant from which it was derived (except if the primordial cell contained some mutation [chimerism]). Normally, such species may also have sexual reproduction as a natural option. Potato, for example, may form berries with true seeds, and strawberry produces fruits with seeds. Such seeds produce genetically heterogeneous progeny because of segregation, since most clonally reproducing species have a high level of heterozygosity. Plants from natural clonal tissues are usually vigorous and can produce flowers and fruit in the same or next season. Plants derived from true seeds of those same species often have a long juvenile stage, and take long to reach commercially interesting size (orchids, tulips, chrysanthemum, potato). The same is true for species that naturally do not reproduce clonally, but as crops which have been reproduced that way for a long time. Examples are apple, rose, and ornamental trees and shrubs, which are reproduced by grafting or cutting.