Abstract
Cytological studies were made on the highly fertile progenies of the amphiploids (10x=70) produced from the interspecific hybrids between tetraploid (4x=28) and hexaploid (6x=42) species of Avena. These progeny lines were derived through ten to twelve generations of inbreeding and selection for fertility and vigor.
Of fifteen lines examined, twelve had chromosome numbers varying from 2n=53 to 58, one had 50 to 52, and two had 42 chromosomes, as the result of chromosomal elimination in the preceding generations. The meiotic behavior of chromosomes was more regular in the plants with 42 chromosomes than in those with 54, 56 or 58 chromosomes. The progeny of the amphiploid oats tended to be cytogenetically stable on either octoploid or hexaploid level.
Cytological observations in the F1 hybrids between different octoploid lines revealed that they are mutually different with respect to a few to several chromosomes. Pairing configurations of chromosomes in the F1 hybrids between the octoploid derivatives and the parental hexaploid species suggested that the octoploids possess all the three genomes of the natural hexaploids, although structural modifications have taken place probably in some of the chromosomes. One of the derived hexaploid lines was phenotypically similar to the parental hexaploid species, whereas the other possessed the characteristics of the both tetraploid and hexaploid parents. Cytological data from the testcrosses showed that the derived hexaploids have the same genome constitution with the natural hexaploids, except for one or two structurally modified chromosomes.
The consequences of new synthetic oats are discussed in relation to the genome constitution.
