SIX CHROMOSOME TYPES IN TRITICUM ARARATICUM JAKUBZ. DIFFERING WITH RECIPROCAL TRANSLOCATIONS

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Abstract
The chromosome structures of 8 strains of T. araraticum collected in southeastern Turkey and northern Iraq were analyzed by hybridization with 3 chromosome type tester strains: the A type of araraticum 196-1, the B type of timopheevi 107-1 and the C type of araraticum 1908A. Concurrently, the chromosome pairings of hybrids of 8 araraticum strains were observed. Of the 8 strains studied, 4 were the B type. The remaining 4 strains were classified into 3 chromosome types different from the A, B and C types. These were designated the D, E and F types. A tetravalent was formed in the PMC [pollen mother cells] of hybrids between the B and D types and between the B and E types. A hexavalent was observed in hybrids between the D and E types, the E and F types, and the B and F types. Two tetravalents were recognized in hybrids between the A and D types and the C and E types. A hybrid between the D and F types showed an octavalent formation at meiosis. A tetravalent and a hexavalent were observed in a hybrid between the A and F types. Reduced seed fertility in hybrids of the strains of T. araraticum apparently is caused by meiotic irregularities such as polyvalent formations. The seed fertilities of hybrids between the B type strains of T. araraticum and T. timopheevi varied from almost sterile to fully fertile. An anaraticum strain collected near Hozat, Turkey, was fully fertile when crossed with T. timopheevi. This provides evidence for the theory that T. araraticum is the ancestral species of cultivated T. timopheevi. Chromosome differentiation in T. araraticum is more abundant in northern Iraq than in Transcaucasus, indicating that the Timopheevi group of tetraploid wheats first originated in the eastern part of the Fertile Crescent and that later its distribution area was extended northward to the Transcaucasus.