Chin-Yi Lu

Improved efficiency of somatic embryogenesis and plant regeneration in tissue cultures of maize (Zea mays L.).

SummaryImmature embryos of eleven cultivars of hybrid maize (Zea mays L.), cultured on 2,4-D-containing nutrient media, showed rapid proliferation of the scutellum and improved efficiency in the formation of embryogenic callus and somatic embryos. High concentrations of sucrose were found to be most favorable for the formation of the embryogenic callus. Embryoids obtained in cultures of all eleven cultivars germinated in vitro and produced normal green plants which were grown to maturity in soil. The effect of genotype and other factors on somatic embryogenesis in maize are discussed.

Isolation and culture of protoplasts of Panicum maximum Jacq. (Guinea grass): somatic embryogenesis and plantlet formation

Summary Protoplasts were isolated from predominantly embryogenic cell suspension cultures derived from proliferating immature embryos and young inflorescences of Panicum maximum Jacq. (Guinea Grass). A large number of protoplasts divided in a liquid culture medium to form hundreds of embryogenic cell aggregates and many globular embryoids. Upon transfer to an agar medium an embryogenic callus was obtained which differentiated more organized embryoids. These embryoids subsequently germinated precociously to form green plantlets. The importance of using embryogenic cell suspensions as a source of totipotent protoplasts of cereals and grasses is emphasized.

Histology of somatic embryogenesis in cultured immature embryos of maize (Zea mays L.)

SummaryThe developmental histology of somatic embryo (=embryoid) formation in cultured immature embryos of hybrid maize cultivars (Zea mays L.) is described. Embryos cultured on media containing 2% sucrose formed distinct globular embryoids. These embryoids arose either directly by divisions confined to the epidermal and the subepidermal cells at the coleorhizal end of the scutellum or from a soft and friable embryogenic callus produced by them. On media containing 6% sucrose divisions were initiated in the cells adjacent to the procambium of the cultured embryos. Subsequently, zones of meristematic cells also were observed in the region of the node and in the basal portion of the scutellum. Mature, well organized somatic embryos as well as a compact nodular type of embryogenic callus were produced as a result of localized meristematic activity along the tip of the scutellum toward the coleorhiza. Some embryos formed only the compact type of callus, and shoot primordia were organized later in the surface layers of this callus.

Uniformity of plants regenerated from somatic embryos of Panicum maximum Jacq. (Guinea grass).

SummaryPlants were regenerated by somatic embryogenesis from cultured leaf segments of Panicum maximum Jacq. (Guinea grass). All plants were phenotypically similar to the donor plant from which expiants were obtained for culture. Examination of the cytological and morphological characteristics of the regenerated plants did not show any changes in mitotic (root tip) chromosome number, structural rearrangements of chromosomes, pollen stainability and morphological characteristics.

Somatic embryogenesis and plant regeneration from cultured immature embryos of rye (Secale cereale L.)

Somatic embryogenesis was initiated in immature embryos of rye (Secale cereale L.) cultured on Murashige and Skoogs (1962) medium supplemented with various concentrations of 2,4-D and sucrose. The developmental stage of the embryo (optimal embryo length 0.5-2.0 mm) and concentration of 2,4-D (optimal concentration 2.5 mg · l(-1)) were found to be critical in determining embryo response. The phenoxyacetic acids, 2,4-D, 2,4,5-T, and MCPA were more effective in initiating embryogenic callus and embryoid formation than other auxins (NAA, IBA, IAA, IPA). Embryogenic callus and embryoid production was greater in embryos cultured scutellum up, and more embryoids were formed in the dark than in the light. Embryoids germinated after transfer to basal medium with/without cytokinin or GA3. The regenerated plants were grown to maturity in soil and were shown to have the normal diploid chromosome number of 14.

Plant regeneration from stem and petal of carnation (Dianthus caryophyllus L.)

Plants were regenerated via adventitious shoot initiation from petal explants of carnation (Dianthus caryophyllus L.) cultivars Crowley Sim, Ember Rose, Orchid Beauty, Red Sim, White Sim and from stem segments of Crowley Sim, Red Sim, White Sim. Differences in cultivar response were observed, with White Sim being the most responsive for both explant types. Plants were also regenerated from receptacles of this cultivar. The effect of different cytokinins on regeneration from petal and stem explants of cultivar White Sim was compared. Thidiazuron was more effective than 6-benzylaminopurine or kinetin. In stem explants, morphogenic capacity was determined by the developmental stage of the explant. Highest percentage of shoot formation was observed in the youngest stem segments, on all the cytokinins tested. Stem-derived plants grew faster than petal or receptacle-derived plants and produced normal, flowering plants eight to ten months after culture.

BIOTECHNOLOGY IN ORNAMENTAL HORTICULTURE

SummaryGenetic engineering techniques have so far had limited impact in the field of ornamental horticulture. As outlined in this review, transformation systems and potential genes of interest are available. As the development of new, novel varieties is an important driving force in the industry, there are, therefore, good prospects for the development of genetically modified ornamental variaties. The few products in the market to date may simply be a reflection of the relatively small scale of the industry compared to the major food crops, and the wide diversity of species within it. Commercial issues attendant to the use of gene technology in ornamental plants need careful consideration. These include careful choice of crop and background variety, the international regulatory process and freedom to operate.

Florigene Flowers: From Laboratory to Market

Plant biotechnology has opened up new ways for the production of crops with improved traits. It is also a useful tool for the breeding of flowers. The floriculture industry is driven by novelty. New varieties are most easily distinguished by new color but plant and flower form, variegation, fragrance, longevity, hardiness and resistance to insects and pests are also important.