Abstract
With the purpose of breeding the amphidiploid, the writer studied genetically and cytologically F1 and F2 plants raised between T. turgidum (n=14) and S. cereale (n=7).
One of the three F1 individuals raised in 1941 was fertile and the other two sterile.
The F1 plants resembled morphologically rather rye, but between fertile and sterile F1 plants differences in external characters were scarcely noted.
The number of somatic chromosomes of the fertile F1 plant is 21, the sum of the gametic number of chromosomes of their parents. The fertile F1 plant showed fertility, though partially, by self pollination, and 68 seeds were obtained from 284 spikelets. This fertility corresponds to 23.94% as calculated to the number of spikelets, 42 F2 plants were raised from these seeds.
The maturation division in P.M.C-s of the fertile F1 plant may be classed into two types, i. e., A-type which gives rise to the pollen grains with the number of chromosomes nearly equal to 21/2, and B-type which results in the pollen grains with the number of chromosomes 2n or approximately equal to it. The course of maturation division of A-type was alike to that of the sterile F1 plants.
In more than half of the pollen mother cells, the course of B-type was observed. In B-type both the non-conjugation and the formation of restitution nucleus were observed.
The pollen grains with 2n chromosomes, produced through the course of nonconjugation and restitution nucleus contain A B genoms from T. turgidum and R genom S. cereale. They play an important role in the formation of amphidiploid.
The number of somatic chromosomes of F2 plants varied from 41 to 45. Plants with 42 somatic chromosomes were prevalent in F2 reaching to 66.67%.
Hyper and hypo-ploid plants resulted from the abnormality in the maturation divisions of F1 were found frequently in F2.
In F2, some plants having 41 or 42 somatic chromosomes showed some fertility. No evident differences were found in external characters among the plants showing 2n=41 and 42, and also among the fertile and sterile plants.
