| Isozymes of Ae. triuncialis and its parental species
Y. NAKAI Laboratory of Genetics, Faculty of Agriculture, Kyoto University, Kyoto 606, Japan A large interspecific variation was found in two genera, Aegilops and Triticum (NAKAI and TSUNEWAKI 1971). Aegilops triuncialis has the genome formula, CCCuCu and is assumed to have originated from the hybrid between Ae. caudata(CC) and Ae. umbellulata (CuCu) (SEARS 1939, KONDO and KIHARA 1943). In one of the many recent studies on the relationships between phosphatase isozymes and phylogeny, BREWER (1969) indicated that in bread wheat part of the alkaline phosphatase activity is controlled by genes on chromosomes 4B and 4D. In our previous work (NAKAI et al. 1969), esterase zymograms of Ae. triuncialis, obtained with pH 3-10 carrier ampholite, showed a good correspondence to those of Ae. caudata and Ae. umbellulata. WAINES and JOHNSON (1971) also found that the electrophoretic pattern of seed protein in an amphidiploid between Ae. caudata and Ae. umbellulata is very similar to that of Ae. triuncialis. I. Esterase isozymes The materials used were about 100 mg of germinating seeds soaked in petri-dishe for 24 hours in a growth chamber (23C). Electrophoresis and esterase analysis were performed with the polyacrylamide disc isoelectrofocusing technique used by NAKAI & TSUNEWAKI in 1971. Two kinds of ampholite with differing pH ranges were used. The results were somewhat different, and are described separately. Results with pH 5-8 carrier ampholite: Zymograms of Ae. caudata (2n=14) and Ae. umbellulata (2n=14) differed. Almost all strains of Ae. caudata (10 strains in total) showed the same esterase zymogram (Fig. 1a). Highly active bands were found at pI 6.7, 6.9 and 7.2, and bands of low activity at pI 5.3, 5.7, 6.0, 6.3, 7.4 and 7.6. Whereas, Ae. umbellulata showed three highly active bands at pI 6.0, 6.2 and 6.5, and a band at pI 5.7 with low activity (Fig. 1b). The esterase pattern of a 1 : 1 mixture by weight of these two species was compared to esterase patterns of two artificialy synthesized CCCuCu strains (KONDO'S and SEARS' strains), and natural Ae. triuncialis (Fig. c-i). The mixture showed a zymogram equal to the sum of both parents, Ae. caudata, Ae. umbellulata (Fig. 1c) zymograms. The two synthesized CCCuCu strains resembled each other, though the pI 6.95 band of SEARS' strain was much weaker than that of KONDO'S. Natural strains of Ae. triuncialis are classified in two subspecies based on their morphological characters; ssp. eu-triuncialis (var. typica) and ssp. orientalis (var. persica and assiriaca). Esterase patterns (Fig. 1f-h) can be classified into three types. Type 1(two strains from Rumania) showed five bands at pI 6.0, 6.2, 6.4, 6.6 and 6.65 (Fig. 1f). These strains belong to ssp. eu-triuncialis var. typica, and their zymogram is the same as that of the synthesized strains. Type 2 (also, ssp. eu-triuncialis var. typica) showed five bands at pI 6.0, 6.3, 6.6, 6.9 and 7.2 (Fig. 1g). The characteristic of band at pI 6.0 separated two bands by condition. This zymogram is similar to that of the 1 : 1 mixture of the two parental species. While, ssp. orientalis var. persica showed five active bands at pI 6.0, 6.2, 6.5, 6.75 and 7.3, weak bands at pI 5.8, 6.4, 6.8, 7.5 and 7.6 (Fig. 1h), only once in the trial did KONDO'S CCCuCu strain show a similar pattern (Fig. 1i). Two bands at pI 6.4 and 6.8 were never found in either Ae. triuncialis ssp. orientalis or the 1 : 1 mixture. Result with pH 6-8 carrier ampholite : A photograph of zymograms obtained with this ampholite is shown in Fig. 2. The 1 : 1 mixture, KONDO'S CCCuCu and Ae. triuncialis var. typica all showed the same zymograms, identical to the sum of the zymograms of both parental species. Rumanian strains and the var. persica of Ae. triuncialis showed different zymograms. SEARS' CCCuCu had a somewhat similar zymogram to that of the Rumanian strains of Ae. triuncialis. The difference found in zymograms of two strains of CCCuCu may be due to a difference in the parental materials used for their synthesis. Parental strains (both for Ae. caudata and Ae. umbellulata) of SEARS' CCCuCu were not available in this experiment. Ae. caudata populations, particularly, may be due to interspecific variations by outcrossing many times in the field, therefor, the genetic background is heterogenous. But, in this experiment, many strains of Ae. caudata were not used. Results indicated that ssp. eu-triuncialis and ssp. orientalis of Ae. triuncialis differed in their esterase zymograms. SENJANINOVA-KORZAGINA (1932) treated ssp. orientalis var. persica as an independent species, Ae. persica, based on her Karyo-morphological study. ZOHARY and FELDMAN (1962) concluded that the ear type of var. persica is due to an introgression of genes from Ae. crassa. KIHARA et al. (1965), on the other hand, suggested that ssp. orientalis derived from ssp. eu-triuncialis. The present results favor KIHARA'S hypothesis that ssp. eu-triuncialis is a progenitor type in Ae. triuncialis. |
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