PRIVATE
NURSING-MEDIA
COMPOSITIONS AND METHODS FOR THEIR USE
FIELD OF THE
INVENTION
This
invention relates to nursing media and to methods for promoting callus
formation and increasing efficiency of plant regeneration utilizing nursing
media.
BACKGROUND OF THE INVENTION
Callus
culture is one of the most important plant science techniques for developing
clonal populations, plant regeneration, and genetic manipulation. This technique is essential for
propagating large numbers of plants with desired characteristics and for
producing plants transformed with new traits introduced through recombinant DNA
technology.
Callus
cultures can be initiated from a variety of explants including stem, petiole,
leaf, rhizomes, roots, fruits, endosperm, seeds, hypocotyl, epicotyl,
cotyledon, meristems, immature and mature embryos, immature inflorescence,
microspores, and the like. The
explant is maintained on a nutrient medium in
vitro in a process designed to produce dedifferentiated tissue, or callus
tissue, a largely unorganized proliferating mass of parenchyma cells from which
plants can be regenerated.
Callus
tissue is useful in studying a number of physiological and developmental
processes in plants, including dedifferentiation and differentiation, embryogenesis,
regeneration, and organ formation.
In addition, callus tissue is important in genetic studies and in plant
breeding. For example, callus
tissue is used to study mutagenesis followed by the isolation of new mutants,
in studies of somaclonal variation, for interspecific hybridization and haploid
plant production, and in various studies requiring a shorter breeding
cycle. Callus tissue is utilized
in cryopreservation studies, plant pathology studies, and for protein
extraction and isolation. For a review
of callus culture and its uses, see Indra, ed. (1984) Cell Culture and Somatic Cell Genetics of Plants, Vol. 1 (Academic
Press, New York) and Green et al.
(1987) Plant Tissue and Cell Culture
(Alan R. Liss Inc., New York).
Callus
culture is also important for plant transformation. Both monocot and dicot callus tissue are used in plant
transformation protocols. Callus
tissue serves as a target for transformation by ballistic particle
acceleration, and the formation of callus tissue may serve as an intermediate
step in the recovery of transformed plants following Agrobacterium-mediated transfer of DNA. Transformation methods for important crops such as maize,
wheat, canola, rice, soybean, tobacco, cotton, sorghum, sunflower, and barley
may involve callus culture at some step in the overall transformation process
for traits including, but not limited to, insect resistance, disease
resistance, herbicide resistance, increased yield, increased tolerance to
environmental stresses (such as drought, heat, etc.), enhanced seed quality
(such as increased or modified starch, oil, and/or protein content), and the
like. Also, callus tissue is used
in assays to assess transient gene expression and to evaluate prom...