| Influence of alien cytoplasms on callus proliferation
and streptomycin resistance in common wheat Toshiro KINOSHITA & Tetsuo MIKAMI Plant Breeding Institute, Faculty of Agriculture Hokkaido University, Sapporo, Japan It is important to know the alloplasmic effects for the manifestation of characters both at cellular and whole plant levels. The seeds of eighteen kinds of allo- or euplasmic lines were provided by the courtesy of Dr. Tsunewaki and used for this investigation. These lines have a common nuclear genotype of 'Chinese Spring' (abbereviated as CS). Murashige and Skoog (MS) medium containing 2 mg of 2, 4-D (2, 4-dichlorophenoxy acetic acid) per liter was used for the seed callus initiation and tissue cultures. Callus culture bioassays were performed by transferring small callus pieces, each weighing approximately 50 mg, onto MS medium with the addition of 0, 125, 250 or 500 ppm of streptomycin sulfate. Callus cultures were incubated in darkness at 26C for 74 days before measuring callus for fresh weight and the resistance index was exhibited as the percentage of the weight measured after the treatment to those of control calli grown in the absence of streptomycin. In correspondence to the examination at callus level, the germinating ability and streptomycin resistance at seedlings were evaluated using the same materials. Although there was no marked difference as to the callus initiation and the morphological characteristics of callus irrespective of allo- or euplasmic lines, the growth rates were remarkably reduced in seed calli of several alloplasmic lines. It is probable that the reduction of callus growth may arise from the physiological nature of the specific alloplasmic lines and the cytoplasmic factors may insert their effects on the ability of callus proliferation in co-operation with the genotype of CS. It is also noted that the proliferation of the seed calli has some relation with the initial growth of radicle in the germination. In both cases, euplasmic line indicated the best growth. The delay of growth in (crassa) CS and (ovata) CS were conspicuous in both characters. It is recognized that (ovata) CS shows slow growth in the spring and delayed heading at plant level. Streptomycin resistance can be used as a marker for selection of somatic hybrids in culture. In this experiment, a considerable increase of streptomycin resistance was observed in (ovata) CS both at cellular and plant levels. In addition, several alloplasmic lines showed a high resistance though the growth rate of calli was relatively low. This is deduced from the fact that streptomycin will prevent active cell divisions as its effect. It is concluded that the cytoplasmic factors from the alien species are deeply related to the physiological nature such as callus growth and streptomycin resistance. Thus, cytoplasmic genes may insert their various effects both at cellular and plant levels in co-operation with nuclear genes. |