Yuzo Futsuhara

Efficient Plant Regeneration by Somatic Embryogenesis from Root Callus Tissues of Rice (Oryza sativa L.)

Summary Embryogenic callus which was compact and white to pale-yellow in appearance was obtained from root sections of rice ( Oryza sativa L.) cultured on Murashige and Skoogs (1962) medium supplemented with 3 mgl- 1 2,4-dichlorophenoxyacetic acid (2,4-D). Embryo-like structures were formed by the callus during one to several subcultures on a medium with no or reduced 2,4-D and supplemented with kinetin. Well formed bipolar somatic embryoids with a plumule and radicle axis surrounded by a scutellum could be easily isolated from the tissue mass. Some aberrant somatic embryoids were also observed. Embryogenic capacity of the rice root cultures was very high, resulting in the regeneration of many plantlets from the two varieties tested. Regenerated plantlets were phenotypically similar to seed derived plants. Plant type, grain filling and other morphological characteristics were normal and uniform.

Histological and scanning electron microscopic observations on plant regeneration in mungbean cotyledon (Vigna radiata (L.) Wilczek) cultured in vitro

Explanted cotyledons of mungbean Vigna radiata (L). Wilczek, variety Pag-asa-1, regenerated shoots directly from the basal adaxial side of the petiolar residue on MS medium supplemented with 8.9 μM 6-benzyladenine. A simplified and rapid procedure for glycol methacrylate sectioning for histological observations was used to observe shoot initiation. At the time of culture, comparatively smaller and differentially stained epidermal cells were present on the basal adaxial region of the petiolar residue. A meristematic cell mass that developed at 48 h after culture appeared to be of epidermal and subepidermal cell origin. Scanning electron microscopy revealed shoot primordia and approximately 2 nodules at the base of the petiole as early as 48 h after culture. All of these structures developed into shoots during incubation.

Comparative studies of organogenesis and plant regeneration in various soybean explants

Abstract Various explants were compared for organogenesis and plant regeneration in soybean ( Glycine max Merr.). Young cotyledons produced organogenic calli, from which adventitious buds and shoots were produced by culture in vitro. Flowering and pod development were observed on regenerated shoots even in vitro, but the recovery of plants was very inefficient. Histological studies revealed weak connections of the regenerated bud primordia with other differentiated tissues, which might be the main handicap to plant recovery in this culture system. Plant regeneration could also take place on the plumule of young embryo explants. The regeneration process started with the enlargement of the plumule followed by the production of adventitious buds. Adventitious buds regenerated much more readily from cotyledonary nodes and some from the plumules in mature embryo explants. An improved culture protocol for efficient plant regeneration in soybean by culturing explants from mature embryos and acclimatizing regenerated plantlets at the early stage is proposed.

Inhibitory effects of volatile compounds released from rice callus on soybean callus growth: allelopathic evidence observed using in vitro cultures

Abstract When soybean ( Glycine max Merr.) callus was cultured with rice ( Oryza sativa L.) callus in the same culture bottle, an allelopathic evidence of growth inhibition on the former callus was observed. This allelopathic effect was so intense that the growth rates of the soybean callus were reduced by more than 100 fold under may experimental conditions. Further studieds showed that the inhibitory effect was from volatile compounds which were produced by rice callus. In rice cell suspension cultures, the volatile inhibitory compounds were released from rice cells and maintained in the liquid medium rather constantly. These compounds in the supernatant fluid from rice cell cultures were quite heat- and acid-stable, but their activity was reduced considerably by KMnO 4 oxidation. On the contrary, the addition of base to the supernatant fluid greatly enhanced the production of volatile inhibitory material. Limited experiments indicated that the allelopathic effect of inhibition on soybean callus was non-specific with respect to rice cultivars. The intensive inhibitory effect was also observed on callus of other legume species as wella but not on members of the Solanaceae. The species-specific inhibitory effect of allelopathy on cultured cell and callus growth may be useful as a strategy for screening somatic hybrid cells from cultures of fusion-treated protoplasts.