Perhaps the most important, in fact revolutionizing, of achievements in horticulture during 1977 was the progress made toward propagation of plants by plant cells and tissue culture commonly called tissue culture). With issue culture, almost endless multication of uniform, disease-free plants can be produced from a very mail mass of parent tissue. Any part of a plant may be used to produce new plantlets - leaf, stem, bulb sheath, or flower. Even a single cell from any part of a plant is capable of growing and differentiating into all parts of a new plant identical to that from which the cell was taken.
The ideal tissue, however, comes from the very end of a plant's growing tip, according to Dr. August Kehr, staff reseacher, USDA Research Service, Beltsville, Md.This is the only part that would be free of viruses that could be perpetuated along with the emerging plantlets.
Use of shoot tips for reproduction makes it possible to eradicate diseases from plants like gladiolus, geraniums and orchids of which some older varieties are totally infected. Through tissue culture, it is possible to develop a virus-free clone .
"In 1977 plant tissue and cell-culture techniques have advanced to the stage at which their application to commercial nursery production is in actual practice," said Dr. Kehr.
"These uses include opportunities for: 1) Rapid plant propagation; 2) Eradication of viruses and other plant desease organisms from named cultivars that have become universally infested in the years since they were developed: 3) Production of true breeding plants: 4) Long-time, low cost storage of nursery crop germplasm for future generations: 5) Transfer of genetic characteristics, such as nitrogen fixation, from one plant to another, and 6) More efficient methods of plant breeding."
It had been assumed that tissue culture might not work with most woody plants. There have been two major problems, according to Dr. R. M. Skivin, University of Illinois professor of horticulture." "It is dificult to obtain uncontaminated cultures from mature plants, even after disinfection," Skivin says. "And many woody plants seem to lack the ability to produce roots and shoots from callus.
"Only recently have investigators seriously attacked the strenuous task of developing intact plants from tissue pieces of woody plants. Success has been reported with eucalyptus, certain types of citrus, poplar, hazelnut, koa and almond.
"The almond belongs to the rose family,which includes many of our most important fruit corps, so it seemed reasonable to expect that the peach, a rose-family member, should grow well in tissue culture."
It was attempted at University of Illinois and was successful; now it seems likely that large numbers of disease-free varieties of peaches can be available throughout the world.
An experimantel USDA vineyard in Silver Run, Md., contains 65 grape vines that began less than a year ago in a research laboratory as just one cubic centimeter of grape-vine tissue.
Dr. William R. Krul, USDA researcher, is still harvesting hundreds of tiny grape plantlets from the original cubic centimeter of cells in his laboratory.
By adjusting the nutrient medium in test tubes, Krul can induce undifferentiated cells, called callus tissue, to form embryos, which can then be cultured into mature vines.
Krul's vineyard is the first in the U.S., perhaps in the world, consisting of vines grown entirely from isolated cells. The experimental vineyard is expected to be at full production by the summer of 1980.
Thousands of grape vines can be produced from a single tissue culture in half the time it takes to propagate a few hundred vines by stem cuttings, the conventional way to propagate grapes, Krul says.