Читать книгу Principles of Plant Genetics and Breeding - George Acquaah - Страница 340

Preexisting meristems are used to initiate shoot culture (or shoot‐tip culture). The size of the shoot tip ranges between 1 and 10 mm long. Cytokinin is used to promote axillary shoot proliferation. Some species (e.g. sweet potato) do not respond well to this treatment. Instead, shoots consisting of single or multiple nodes per segment are used. These explants are placed horizontally on the medium and from them single unbranched shoots arise that may be induced to root to produce plantlets.

Shoot tips are easy to excise from the plant and are genetically stable. They contain pre‐formed incipient shoot and are phenotypically homogeneous. These explants have high survival and growth rates. Axillary and terminal buds have the advantages of shoot tips, but they are more difficult to disinfect. On the other hand, meristem tips contain preformed meristems and are genetically stable and phenotypically homogeneous, but are more difficult to extract from the plant. Further, they have low survival rates. Meristems in general tend to be free of virus infection, even if the rest of the plant is infected. Meristems may therefore be the ideal explant to cure virus infected valuable clones.