| Telocentric chromosomes were found in one plant from the 42 x 41 cross (2.4%) and
none in the reciprocal cross. In the 43 x 42 cross 14 out of 38 plants studied had 43 or other hyperploid chromosome numbers (36.8%), and 55.3% plants were 2n=42. In the reciprocal cross, 42 x 43, the frequencies of hyperploids and euploids were 30.5% and 61.0% respectively. Hypoploids were found in both cross combinations; 7.9% in the former cross and 8.5% in the latter. The frequencies of 43- and 42-chromosome plants were similar to each other in both cross combinations as shown in Tables 3 and 4. This result suggests 22-chromosome gametes might be able to compete well to 21-chromosome normal gametes in fertilization. Telocentric chromosomes were also found in 5.2% plants in the 43 x 42 cross and 8.6% in the reciprocal cross. The frequency of plants with telocentric chromosome is much higher in crosses involving 43-chromosome plants (6.6%) than in those involving 41-chro mosome plants (0.93%). Out of four plants from the 44 x 42 cross in UM 6250 (C group), three plants were 2n=42 and one was 2n=43. In one cross of 43 x 43 in UM 6408, the numbers of 43-, 42- and 41-chromosome plants were 3, 2 and 1, respectively. Nine plants from a 42 x 42 cross in UM 6211 were all 2n=42. Seven plants from a 41 x 42 cross showed different results from all other cross combinations similar to this; three plants had 2n=40+1 telo, two had 41+1 telo, one had 42+2 telo, and the last one plant had 42 chromosomes. This result could be explained by the assumption that the 42-chromosome plant used as a pollen parent was actually 2n=40+2 telocentric chromosomes. However, the possibility could not be ruled out that the female parent had 2n=40+1 telocentric chromosomes instead of 2n=41. The authors wish to thank Mrs. F. NICHOL for her technical help in chromosome studies. Literature TSUCHIYA, T. 1968a. Chromosome variations in some strains of hexaploid Triticale. Wheat Inf. Serv. 27: 7-8. TSUCHIYA, T. 1968b. Breeding behavior of aneuploids in some hexaploid Triticale. Wheat Inf. Serv. 27: 9-10. |
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