Shigeatsu MATSUBARA and Ichiro OHTSUKA
Lab. of Plant Breeding, Hokkaido Univ., Sapporo and Kihara Institute for Biological Research, Yokohama
In order to determine the cytoplasmic control of Aegilops squarrosa (2n=14; DD) on chromosome pairing, fertility and chromosome transmission, the AABBD pentaploid lines having squarrosa cytoplasm were produced from the crosses of alloplasmic Dinkel having squarrosa cytoplasm x Emmer, and alloplasmic Emmer x Dinkel. As the parental lines, Triticum spelta var, duhamelianum (6x), T. vulgare var. erythrospermum (6x), T. polonicum var. vestitum (4x), T. durum var, reichenbachii (4x) and their alloplasmic lines having squarrosa cytoplasm were used. Germination ability, chromosome configuration in PMC's, pollen fertility and selfed seed-set of the (squarrosa)-5x lines were compared with the respective control 5x lines having Dinkel or Emmer cytoplasm.
There was a significant reduction of germination rate of 5x hybrid seed in 4x (female) x 6x (male) in comparison with that of 6x (female) x 4x(male), but no difference was detected between 5x lines having squarrosa cytoplasm and those having Dinkel or Emmer cytoplasm. On the other hand, significant differences were observed in pollen fertility between (squarrosa)-5x and (wheat)-5x, 35.4% and 82.5% on average, respectively. Also, significant increase of trivalent formation in PMC's at MI was observed in three (squarrosa)-5x lines in comparison with respective controls.
Equation and certation crosses were conducted by crossing (squarrosa)-5x lines with T. durum or T.v.e. reciprocally. A part of data were shown in Table 1 and Fig. 1. The data on chromosome transmission indicate that no 14-chromosome gamete was transmited through male in (squarrosa)- 5x, and significant reduction was observed in transmission rates of 14- and 15-chromosome gametes through female in equational crosses involving (squarrosa)-5x in comparison with those of the control 5x. In certation crosses involving (squarrosa)-5x, the following formulas were introduced for calculating the chromosome transmission rates on the assumption that 1D chromosome is essential to avoid incompatibility between the nuclear genome and squarrosa cytoplasm (OHTSUKA 1980);
The observed data fit well the theoretical ones as seen in Fig. 1.
Conclusionaly, the experiment showed that male gametic sterility and zygotic lethality were detected in the interaction between squarrosa cytoplasm and AB genome, and that the squarrosa cytoplasm affect the chromosome paring, fertility, and chromosome transmission to the progenies in 5x hybrid of wheat.