| Thirtyfive-chromosome plants obtained by successive
deletion of A-genome chromosomes from common wheat S. SHIGENAGA Experimental Farm, Kyoto University Takatsuki, Osaka, 569 Japan In the process of successive deletion of A-genome chromosomes from Chinese Spring wheat by using nullisomic lines (MOCHIZUKI and SHIGENAGA 1964), three kinds of sextuple monosomics were crossed with the seventh nullisomics for obtaining the septuple monosomic, that is a pentaploid plant (2n=35, 14"+7', ABBDD). Five 35-chromosome plants could be cytological selected in the F1 (Table 1 and Table 2). Each hypoaneuploid dealt with in the present paper is symbolized for brevity by the letter m and n, indicating the monosomic and nullisomic condition, respectively, followed by the designation of the chromosome for which it is deficient, as was done in the previous papers (SHIGENAGA 1968a, b, and 1976). For exmaple a nulli-3A plant and a plant sextuply monosomic for chromosome 1A, 2A, 4A, 5A, 6A and 7A were designated as n3A and m1Am2Am4Am5Am6Am7A, respectively. Two 35-chromosome plants obtained from the cross between m1Am2Am4Am5Am 6Am7A and n3A, and a 35-chromosome plant from the cross between m1Am2Am3Am4Am 6Am7A and n5A grew well. The former two were designated in this paper as Plant No.1 and Plant No. 2, respectively, and the latter as Plant No. 3. Other 35-chromosome plants died as seedlings. The chromosome configurations, however, were unexpectedly 15"+5' in both Plant No. 1 and Plant No. 2, and 1"' + 13"+6' in Plant No. 3 (Fig. 1). No other configurations than the above in each plant were observed and most bivalents were of the closed type. Trivalents involved in Plant No. 3 were also closely associated and formed figure in the shape of V. |
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