| Intraspecific differentiations in chromosome Structures
of the wild tetraploid wheats Taihachi KAWAHARA and Masatake TANAKA Plant Germ-plasm Institute, Faculty of Agriculture, Kyoto University, Mozume, Muko, Kyoto Intraspecific differentiations in chromosome structures of the two wild tetraploid wheats, Triticum dicoccoides Korn. and T. araraticum Jakubz. were analyzed through hybridization experiments. In T. dicoccoides, three chromosome types differing with reciprocal translocations were reported by KAWAHARA and TANAKA (1978). While, seven chromosome types (A-G type) were found in T. araraticum (TANAKA et al. 1979). In the present study, a total of 190 strains, 40 dicoccodies strains and 150 araraticum, strains, collected from the whole range of their distribution area were analyzed using strains belonging to those chromosome types as tester strains. Two new chromosome types were recognized in T. dicoccoides in addition to the three reported earlier. Those five types were designated from the E1 to the E5 type, respectively. The E1 type was the most common and 80 per cent of the dicoccoides strains observed were of this type. Five strains belonged to the other four types. Three strains from Southern Turkey had chromosome structures other than E1, but their chromosome type remained unidentified. Types other than E1 were restricted to a single locality in Turkey or Palestine, respectively. The number of translocations between the E1 and the other four types was lower than that found among the types other than E1. Based on those observations, the E1 type was considered to have the original chromosome structures. The other four types seem to be differentiated from this original type by one reciprocal translocation. Of the 150 araraticum strains observed, 90 belonged to the B type and seven strains were of the other six types. The remaining 53 strains had chromosome structures other than B, but their chromosome type did not be identified yet. The number of interchanges between the B and the other six types was lower than that found among the types other than B. The B type was found in all the regions where samples were collected. Those observations lead to the conclusions that the B type is the original chromosome structure of T. araraticum and that the other six types were derived from B type by one or two reciprocal translocations. Strains of the derived types were found in the whole distribution area. In Southeastern Turkey and northern tip of Iraq, most strains were of the original type. While, a population in Southern Turkey was marked by its very low proportion of the original type. The present study revealed the wide geographical distribution of the original chromosome types and the sporadic occurence of the derived types in both T. dicoccoides and T. araraticum. This would indicate that the intraspecific differentiation in chromosome structures of the two wild tetraploid wheats occured after the extension of their distribution area from their birthplace, the eastern part of the Fertile Crescent, to the present regions showing disjunct patterns of distribution. |