| Progeny of a haploid common wheat with Aegilops
kotschyi cytoplasm Yasuhiko MUKAI and Masahiro IKEDA Department of Biology, Osaka Kyoiku University, Ikeda, Osaka 563, Japan The cytoplasm of Aegilops kotschyi was introduced into a IB/1R translocation line of common wheat, Triticum aestivum cv. Aurora by repeated backcrosses. In B9 generation, (kotschyi)-Aurora was the 1B/1R homozygote and produced haploids at a high frequency (93.8%). The resulting haploids were backcrossed with normal Aurora pollen. Results of the cross are shown in Table 1. Of 1708 florets pollinated, only 90 set seeds (5.3%). Among them, 19 were germless grains. 71 seeds were sown, of which 63 germinated. The chromosome numbers of plants were determined from root-tip mitosis. 30 were diploid (chromosome number=40-44) and 28 were haploid (20-22). Of five twin paris, four were n-2n type. From the crossed results, the egg cells with chromosome numbers ranging from 19 to 23 could take part in the fertilization. The observed frequency of female gametes with 21 chromosomes was extremely high in comparison with the theoretical one estimated from the binomial distribution. This is mainly due to the production of unreduced gametes following failure of the first or second division during meiosis. And also, the origin of aneuploid gametes (n=20 or 22) may be attributed to abnormal behavior of a univalent in meiotic division as proposed by SEARS (1939). The haploid of (kotschyi)-Aurora had 21 unpaired chromosomes at metaphase I in 54.2 % PMCs, while other had one or two bivalents. Metaphase cells with 21 univalents were of two types: one showed normal univalents, and the other showed univalents with visible chromatids like those at mitotic metaphase. In the latter cells, these univalents divided equationally at the first division, and then restitution nuclei were formed at a low frequency because of an omitted second meiotic division. In fact, at tetrad stage, the frequency of dyads which were thought to be the product of unreduced gametes in microsporogenesis of the haploid was 1.5% (Table 2). Non-pollinated florets of the haploid of (kotschyi)-Aurora were fixed in Carnoy's solution eight days after emasculation. Development of embryo in non-pollinated ovules of the haploid was studied anatomically using ordinary paraffin sectioning method. Of 129 ovules examined, 102 had no embryosac. Parthenogenetic development of embryo was found in five ovules (3.9%). In the remaining 22 ovules, no egg cell was developed. This fact indicates that the haploid formation in the haploid of (kotschyi)-Aurora is due to parthenogenesis of the egg cell similar to that found in the diploid of (kotschyi)-Aurora. The authors wish to thank Dr. I. PANAYOTOV, Institute for Wheat and Sunflower, Bulgaria for supplying seeds of the 1B/1R heterozygous (kotschyi)-Aurora. This study was supported in part by a Grant-in-Aid (No. 57760006) from the Ministry of Education, Science and Culture, Japan. |