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Preliminary report on shoot redifferentiation from
wheat callus H. OGURA* and T. Shimada Laboratory of Genetics, Faculty of Agriculture, Kyoto University, Kyoto 606, Japan It seems to be of valuable importance in basic studies on breeding and genetics of wheat plant to establish the conditions for shoot redifferentiation from wheat callus. However, only a few investigators have reproted occasional shoot redifferentiation from wheat callus of somatic tissue origin, by decreasing auxin level (SHIMADA et al. 1969) or application of zeatin (DUDITS et al. 1975) in the medium. In attempts to improve the conditions for shoot redifferentiation, preliminary data are here presented on the relationship between "callus age" and shoot regeneration, and kinetin- IAA (indole-3-acetic acid) interaction. Presoaked and sterilized seeds of Triticum aestivum cv. Chinese Spring were placed aseptically on an RM-1964 agar slant medium (LINSMAIER and SKOOG 1965) containing 3.0 mg/l of 2,4-dichlorophenoxyacetic acid (2,4-D) and cultured in vitro under continuous fluorescent illumination of about 1,200 luxes and the constant temperature of 25 + or - 1C. The pH of the medium was adjusted to 5.8 + or - 0.1 before autoclaving. Callus formation from germinated seedling roots was observed about 25 days after inoculating the seeds. Primary callus cultures were obtained by transferring these induced callus masses into new fresh RM-1964 medium in test tubes (18 x 180 mm), each containing 10 ml of the same medium as used for callus induction. These calluses were subcultured every ca. two months in the same RM-1964 medium supplemented with 3.0 mg/l, of 2,4-D. and maintained in our Laboratory. Differing callus cultures of other higher plants, the wheat callus cultured in the conditions is especially characterized that roots or root-like tissues were frequently accompanied. When 2,4-D concentration was higher than 5.0 mg/l, comparatively uniform callus with no roots was obtained, but the growth was highly inhibited. In case of shoot redifferentiation experiment, root or rootlike tissue was aseptically removed from the callus by a scalpel prior to inoculation. Effect of callus age, i.e., time length as a callus state before placing onto the shoot redifferentiation medium (RM-1964+2.0 mg/l kinetin+0.2 mg/l IAA), on shoot regenerative ability and green spot formation is presented in Table 1. The data suggest that shoot regenerative ability decreased in proportion to callus age. Calluses cultured for about six months gave rise no shoot. Also, light condition seems to be necessary, because, in the dark, even young-age callus (less than 30 days of culture in the primary subculture medium) significantly decreased shoot formation, and no green spots were formed. Table 2 shows influence of the combination of kinetin and IAA on organ formation from two week-aged callus. It seems there are no significant differences in shoot and root as well as green spot formation due to combinations or concentrations of growth regulators. Almost all calluses with green spots did not redifferentiate shoots. Several combinations of a morphactin, chlorflurenol-methyl-ester (CFM) and kinetin were tested on shoot organogenesis from wheat callus, however, no shoot morphognesis was observed. Several combinations of these substances have been successful for 100% of shoot redifferentiation in tobacco callus (Ogura 1975). So far as the wheat callus of seedling root origin is concerned, the results may be interpreted that shoot regeneration depends on (1) callus age, (2) light condition and (3) medium composition and/or growth regulators. Literature Cited DUDITS, D., G. NEMET and Z. HAYDU 1975. Study of callus growth and organ formation in wheat (Triticum aestivum) tissue cultures. Can. J. Bot. 53: 957-963. LINSMAIER, E. M. and F. SKOOG 1965. Organic growth factor requirements of tobacco tissue cultures. Physiol. Plant. 18: 100-127. OGURA, H. 1975. Morphactin-kinetin interaction on growth and shoot formation m tobacco callus cultures. Plant & Cell Physiol. 16: 563-569. SHIMADA, T., T. SASAKUMA and K. TSUNEWAKI 1969. In vitro culture of wheat tissues. I. Callus formation, organ redifferentiation and single cell culture. Can. J. Genet. Cytol. 11: 294-304. (Received Jan. 24, 1978) |
| * Present address: Laboratory of Crops and Plant Breeding, Ishikawa Pref. College of Agr., Nonoichi, Ishikawa-gun, Ishikawa Pref. 921, Japan. |