Cytogenetics in Plant Breeding Volume 17 1992
Jacob Sybenga

The Mechanisms of Genetic Transmission

Chapter 3

3.1.3.5 Non-Homologous Chromosome Association. Nuclear Compartmentalization

p. 33. According to Pohler and Claus (1985), the cause of genome separation in hybrids between Hordeum species and between Hordeum and Secale was a genomic difference in the timing of anaphase separation. The chromatids of Secale chromosomes separated later than those of Hordeum and were positioned at the periphery of the nucleus. Other irregularities occurred also. Differences in centromere separation have repeatedly been reported by Vig and coworkers (for a review, see Vig. 1983) and may well play a role in chromosome positioning in the resulting daughter nuclei.

The Somatic Chromosome Complement: Karyotype Analysis

Chapter 4

The Somatic Chromosome Complement:

Karyotype Analysis

Markers Within Chromosome Arms

p. 97. By applying purification techniques and later also by cloning in bacterial plasmids, different families of repetitive DNA with specific physical properties could be separated and identified in rye and later also in other Triticinae (Appels et al. 1978; Bedbrook et al. 1980; Flavell 1981; Appels and McIntyre 1985). When these different families were hybridized in situ with denatured rye chromosomes in cytological preparations, it appeared that most of the terminal heterochromatin blocks contained most of the families. It was also shown that removal of small segments from the blocks of heterochromatin tended to remove specific DNA families. This showed that these families did not occur in a mixture, but were physically separated. A few highly repetitive DNAs were restricted to specific interstitial segments and another group was distributed evenly over the chromosomes. Hybridization with related rye species and with wheat showed that even closely related species showed very different patterns of repetitive DNA. Several families are species-specific, but others are shared by species that are not especially closely related, such as rye and wheat.

Manipulation of the Genetic System

12.2.2.2 Inversions

p. 385. As concluded by Sybenga (1969, 1973), the task of regulating pairing for each individual chromosome separately, and of completing the differentiation to a sufficient level by genetic means, is large. Yet, if allopolyploidization is ever to be successful, it may well be that a combination of chromosomal rearrangements, existing genetic diversity and mutagenization is the only way.

The possibility that the much simpler allopolyploidization of only one or a few chromosomes creates a segmental allopolyploid with specific advantages has not been studied.