| A new amphidiploid from the hybrid Ae. sharonensis
x Ae. umbellulata By Masatake TANAKA Lab. Genet., Kyoto Univ., Kyoto According to KIHARA, the genome formula of Ae. variabilis and Ae. Kotschyi is CuCuSvSv. The present writer has produced an amphidiploid from the cross Ae. umbellulata (CuCu) x Ae. sharonensis (S1S1). In 1950, very young seedlings of the F1 hybrid Ae. sharonensis x Ae. umbellulata were subjected to colchicine treatment. In 1951, 12 out of 20 treated plants showed chromosome doubling. The chromosome pairing and the percentage of pollen- and seed-fertility of the F1 hybrid are given in Table 1. The fertility of the amphidiploids is given in Table 2. Data on chromosome pairing and fertility of seed and pollen in the amphidiploids from 1952 to 1954 are summarized in Table 3. Reciprocal crosses between the amphidiploid (S1S1CuCu) and Ae. variabilis were made for testing the chromosome homology (Table 4). The chromosome pairing of these hybrids was almost normal; 9-14 (mode at 13) bivalents were observed. Complexes were found in all individuals. Pollen-fertility was 65-75% and seed-fertility also was relatively high. A cross between S1S1CuCu and Ae. ovata (CuCuMoMo) produced only sterile dwarfs. From these results it became clear that the genomes of Ae. variabilis are homologous to those of the amphidiploid. Ae. variabilis and Ae. Kotschyi must have arisen as an amphidiploid between Ae. umbellulata with CU-genome and Ae. sharonensis with S1-genome in the course of evolution. According to EIG (1929), Ae. umbellulata and Ae. sharonensis are separately distributed. There are, however, three modifications of the S-genome (S,S1,Sb) in the S-group. Some of them (f. inst. S-genome in Ae. speltoides and Ae. Aucheri) occur together with Ae. umbellulata in Asia Minor and Syria. One of them may have been the genome of one of the parents. From the taxonomic view point, the amphidiploid (S1S1CuCu) resembles Ae. Kotschyi in main morphological characters. But, in some characteristics, the synthesized S1S1CuCu is different from Ae. Kotschyi and Ae. variabilis, for example, regarding the number of spikelets in the ear, shape of the awn, etc. |