| Genetic effects of 25 alien cytoplasms on plant height
and its component parts in common wheat Koichiro TSUNEWAKI Laboratory of Genetics, Faculty of Agriculture, Kyoto University, Kyoto, Japan By repeated backcrosses, the cytoplasms of 25 species of Triticum and Aegilops have been introduced into 12 strains of five common wheat species (TSUNEWAKI et al. 1978). The nucleus donors used were as follows: T. aestivum var. erythrospermum, strain P168, cv. Chinese Spring, cv. Norin 26, strain Salmon, cv. Jones Fife, cv. Selkirk, cv. S-615, T. sphaerococcum var. rotundatum, T. compactum cv. No. 44, T. spelta var. duhamelianum, and T. macha var. subletschchumicum. All these cytoplasm substitution lines were grown in an experimental field under a split plot design with four replications, in which 12 nuclei were placed in the major plots and 26 cytoplasms (25 alien and a common wheat cytoplasm) in the subplots. In each subplot two plants were grown, average of which was regarded to represent the subplot value. Number of internodes over 3 cm, lengths of three culm internodes from the top, ear length and plant height were measured in each plant using its tallest culm. Analysis of variance revealed that all six characters were influenced by alien cytoplasms. Average deviations of 12 cytoplasm substitution lines with the same cytoplasm from their corresponding normal lines are shown in Table 1. All nine cytoplasms belonging to A, Cu, M and Sl plasma types reduced every character to a great extent; all reductions were significant at the 1 % level. C and G type plasmas reduced the first internode length and plant height, and most D type plasmas reduced the number of internodes. Mo type plasma increased number of internodes but reduced the first and second internode lengths and plant height. In general, S type plasmas did not show a remarkable effect on any character. From these results it became evideht that cytoplasms of the different types exert very specific effects on plant height and its component parts. A representative cytoplasm was selected from each plasma type, and the relative effects it had on plant height and the component parts were calculated as shown in Table 2. From these data, it became clear that three cytoplasms of Cu, M and Sl type almost uniformly depressed all characters, while the cytoplasms of C, G and Mo type had great influence on only certain characters. Two cytoplasms of D and S type did not show any effect. From those results, we may conclude that A, Cu, M and Sl type cytoplasms depress general growth vigor of common wheat, while C, G, Mo and probably D type plasmas have stage-specific effects on wheat growth: S type plasmas do not have any such effects. In order to reveal the relative contribution of the cytoplasm to genetic variability, genetic variances attributable to the nucleus, cytoplasm and their interaction were calculated, which are shown in Table 3. The variance attributable to genetic differences among the cytoplasms of 26 Triticum and Aegilops species was only 2 to 20%, with an average of 15%, of the variance attributable to the nuclear differences among 12 common wheat strains. This fact supports our general belief that a large part of the genetic variability owes to the nucleus. The present work was carried out with help of Mr.Y.MUKAI, Osaka Kyoiku University, and Dr. T. Ryu ENDO, Nara University, to whom the author wishes to express his greatest appreciation. The work was supported by a Grant-in-Aid (No. 236002) from the Ministry of Education, Japan. Literature Cited TSUNEWAKI, K., Y. MUKAI and T. Ryu ENDO 1978 On the descent of the cytoplasms of polyploid species in Triticum and Aegilops. Proc. V Int. Wheat Genet. Symp. (in press) |