The fertile F
1 plant (TcSF
1-1)
T. compactum (
n=21)×
S. cereale (
n=7) and its offsprings were studied genetically and cytologically with the purpose of breeding the constant type in the descendants.
The number of somatic chromosomes of this F
1 is 28, the sum of the gametic numbers of chromosomes of the parents.
The external characters of the F
1 resembled more closely to
T. compactum than being intermediate between the parents.
The maturation division in PMC-s of the F
1 may be classified into two types A and B. A-type gives rise to the pollen grains having the number of chromosomes 28/2 or nearly so, and B-type results in the pollen grains with the number of chromosomes 2
n or approximately so. In B-type non-conjugation and the formation of restitution nucleus were observed.
The pollen grains having 2
n chromosomes, produced through the course of non-conjugation and restitution nucleus are provided with A B D genoms from
T. compactum and R genom from
S. cereale. These pollen grains play an important role in the formation of amphidiploid.
The number of somatic chromosomes of F
2 plants were 47, 48, 54, 55, 56 and 58. In the F
2 generations hypo and hyper amphidiploid plants resulted from the abnormality in the maturation division of F
1 were frequently found besides the amphidiploids with 56 chromosomes.
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