The distribution of T. palaeocolchicum is restricted in West-Georgia of Trans-Caucasia and overlapped with that of T.timopheevi. Morphologically, T. palaeocolchicum is difficult to be distinguished from T. macha which is the Trans-Caucasian-endemic Dinkel wheat (JAKUBZINER 1958). T. palaeocolchicum appears as a bridging type between T. timopheevi and T. dicoccum (MAC KEY 1963). Therefore, even after the genome of this species was designated as AABB by MATSUMURA (1958), MAC KEY (1963) discussed the phylogenic relationship among T. palaeocolchicum, T. macha and T. timopheevi. The present results indicates the presence of the genetic factor(s) for genome compatibility to the cytoplasm of Ae. squarrosa in T. palaeocolchicum, and suggests that T. palaeocolchicum might receive the genetic factor(s) from T. timopheevi through the introgressive hybridization.

Another Trans-Caucasian-endemic species of T. persicum was also classified as AG type in the present experiment. The status of this species in wheat phylogeny has been discussed frequently after it was discovered. LILIENFELD & KIHARA (1934) included this species in Emmer group. VAVILOV (1926) suggested that T. persicum had originated from a pentaploid hybrid between Emmer and Dinkel wheats. MAC KEY (1963) and KUCKCUK (1979), in studies of the Q factor and resistance to mildew and rust respectively, supported the hypothesis of VAVILOV (1926). Taking together the previous works, there is a possibility that T. persicum obtained the genetic factor(s) for the genome compatibility to the cytoplasm of Ae. squarrosa through the translocation between 1D chromosome and a chromosome of AB genome in the evolution of T. persicum (AABB) from pentaploid hybrid (AABBD).

TANAKA and co-workers collected many strains of wild tetraploid wheats in 'Botanical Expedition of Kyoto University to the Northern Highlands of Mesopotamia' (BEM) in 1970. These strains were classified as T. dicoccoides (AABB) and T. araraticum (AAGG) by the morphological and cytological studies (TANAKA & ISHII 1973; TANAKA & KAWAHARA 1976; TANAKA et al. 1978, 1979; TANAKA & SAKAMOTO 1979). Twenty-seven lines of these wild tetraploid wheats collected by BEM were used in the present experiment. These lines were classified as AB type or AG type depending on the differential response to the cytoplasm of Ae. squarrosa. The results were shown in Table 2 together with the classification of TANAKA and co-workers (1973, 1976, 1978, 1979, and personal communication).

The present classification of AB or AG types agrees with TANAKA's classification of AB or AG genomes in twenty-four strains. However, three strains of KU-8808,-8821 A, and -8821 C which were classified as AABB genome species by TANAKA and co-workers (1976, 1978, 1979) showed AG type response to the cytoplasm of Ae. squarrosa. TANAKA & KAWAHARA(1976), and TANAKA et al. (1978, 1979) classified KU-8821 A and -8821 C as T. dicoccoides (AABB) because these two lines showed morphological similarities and cytological affinities with Palestaine-T. dicoccoides. However, they also observed high chromosome pairing in PMC's of F₁ hybrids between these two strains and Trans-Caucasian-T. araraticum (AAGG), although the F₁ hybrids were completely sterile. The present result also indicates that KU-8821 A and -8821 C are not typical AABB genome species. Since these two strains were collected from the northern highlands of Mesopotamia where T. araratcium distributed dominantly, TANAKA and co-workers (1978, 1979) suggested that T. dicoccoides and T. araraticum were differentiated from a common tetraploid ancestor in that region. The present results of KU-8821 A and -8821 C support the hypothesis of TANAKA and co-workers (1978, 1979).

The present classification of the tetraploid wheats by the response to Ae. squarrosa cytoplasm coincides with the classiflcation of Emmer and Timopheevi groups in most strains. MAAN (1975) and TSUNEWAKI et al. (1976) indicated that the genetic differentiations of the cytoplasms among wheats and its relatives are corresponding to their genomic differentiations. The genetic factor(s) for the compatible relation between the genomes and cytoplasms may reflect the differentiation of the species, and the system used in the present experiments may be useful for the classification among related species of Triticinae.

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