| Studies on the induction of mutations by P32
in wheat : I. Chromosomal aberrations in R2 generation, with special reference to the frequent occurrence of monosomics Yoshio WATANABE and Koichiro MUKADE Laboratory of Wheat Rust Resistance Tohoku National Agricultural Experiment Station, Morioka, Japan From the Seeds of a variety,"Aoba-Komugi ", treated with P32 in 1956, two plants having 2n=42 were chosen: one from the seed treated with 5microc, the other from one treated with 10 microc, respectively. Besides these, a monosomic plant which was found among plants treated with 5 microc was also studied. The meiotic chromosome behaviors of these R1 plants are given in Table 1. In R2 generation,various aneuploids having 2n=40 to 44 were observed as given in Table 2. The types of chromosomal aberrations were translocation, deficiency, nonpairing and their various combinations. But the author's special attention was attracted to the rather frequent occurrence of monosomic plants. Namely, the percentages of monosomics in the R2 generation derived from R1 plant having 2n=42 were 12.77% and 17.74%, respectively. 21.31% of the progenies of a monosomic R1 plant (5 microc) was again monosomic. However, the average percentage of monosomic with 20II + 1I was 11.47% in the progenies of R1 plants with 2n=42, while 6.56% in the progenies of the monosomic R1 plant. Among the R2 progenies derived from the monosomic R1 plant, there occurred the plants accompanying deficiency. |