| Classification of tetraploid wheats based on differential
response of their genomes to Aegilops squarrosa cytoplasm1)
Ichiro OHTSUKA Kihara Institute for Biological Research Mutsukawa 3-122-21, Minami-ku, Yokohama, Japan In 1934, LILIENFELD and KIHARA divided the tetraploid wheats into two groups based on genome analysis; Emmer group with the AABB genome constitution and Timopheevi group having the AAGG genome constitution. Since then, many workers have been discussing on the relationship between these two groups (KOSTOFF 1936; WAGENNAAR 1961, 1966; FELDMAN 1966), because of their genetical similarity and continuous variation. The continuous variations of the cytological and morphological characters between Emmer and Timopheevi groups are more remarkable in their wild species than in their cultivars (TANAKA & KAWAHARA 1976; TANAKA et al. 1978, 1979; TANAKA & SAKAMOTO 1979). Recently, MAAN (1975) and KIHARA & OHTSUKA (1975) reported that the successive back-crossed lines of Emmer wheats to an induced autotetraploid Aegilops squarrosa had 29 chromosomes even after back-crossing more than ten times, and that many abortive seeds were produced in the back-crossed spikes as the result of lethality of zygotes which did not receive an extra chromosome from female gametes. This extra chromosome was indispensable for the compatible relation between the AB genome of Emmer wheats and the cytoplasm of Ae. squarrosa in zygote and in male gamete (OHTSUKA & KIHARA 1976; OHTSUKA 1980). This chromosome was identified to be homologous to 1D chromosome of Dinkel wheat (OHTSUKA & KIHARA 1976; TSUJI & MURATA 1976; OHTSUKA 1980). On the other hand, two alloplasmic lines of Timopheevi wheats (Triticum timopheevi and T. araraticum) with the cytoplasm of Ae. squarossa showed the chromosome configuration of 14II in their PMC's and did not produce the abortive seeds in back-crosses (OHTSUKA 1980). OHTSUKA (1980) suggested that the AG genome of Timopheevi wheats had factor(s) which controlled the compatible relation between wheat genomes and the cytoplasm of Ae. squarrosa. Present experiments attempt to use the differential response of AB and AG genomes to Ae. squarrosa cytoplasm for classifing the tetraploid wheats. Materials and Methods Thirty-nine strains of tetraploid wheat including cultivars and wild species were used as male parent in the crosses. Twenty-seven strains of the wild tetraploid wheat used were collected from northern highlands of Mesopotamia by Dr. TANAKA et al. in the Botanical Expedition of Kyoto University to the Northern Highlands of Mesopotamia (BEM) in 1970. The other strains have been maintained in Kihara Institute for Biological Research. They were shown in the column of male parent of Table 1 and 2. Three species of Emmer wheat (2n=28; AABB), T. turgidum, T. durum, and T. dicoccoides were successively back-crossed to the colchicine-induced autotetraploid line of Ae. squarrosa (2n=28; DDDD). During the back-crosses, Emmer wheat lines of 1D monosomic-addition or 1D(1A) monosomic-substitution having Ae. squarrosa cytoplasm were obtained (OHTSUKA 1980). These lines were designated as (squarrosa) T. turgidum+1D, (squarrosa)T. durum+1D, and (squarrosa) T. dicoccoides+1D-1A, respectively, and used as female parents in the present experiment. The crosses were conducted in 20 to 50 florets/spike, on two or more spikes/individual, with two or more individuals for each combination, in the field at Yokohama. The percentage of abortive seeds in seed-set was scored in the crosses. The tetraploid wheats used as pollen parents were classified as AB type in the response to the cytoplasm of Ae. squarrosa when many abortive seeds were produced in the crosses, and as AG type when the abortive seeds were not produced with some exceptional cases having 2-3% abortive seed production. |
| 1) The present study was conducted as a part of the Cooperative Project on NC-Heterosis Breeding directed by Dr. H. Kihara, and financially supported in part by the Grant-in-Aid No. 1445 (1980) of Ministry of Agri. Forest. and Fish. of Japan |
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