Abstract
SUMMARYKaryotypic analysis of the F1 hybrid (Ae. speltoides x T. boeoticum) and data on the microsporogenesis of the hybrid and of the amphiploid obtained by chromosome doubling with colchicine, are reported. Chromosome morphology, relative length of each genome and pairing behaviour are discussed in parallel, both in the artificial allotetraploid and in tetraploid wheats, particularly in relation to origin and differentiation of the two main groups of wheat belonging to T. turgidum and T. timopheevi respectively. From analysis of the data, the following conclusions can be drawn: 1) Chromosome morphology of T. boeoticum and Ae. speltoides is clearly different from that presented by T. turgidum. 2) A similar distinction — even if at a lower degree — was found in respect to T. timopheevi. 3) Morphology differentiation of chromosome seems to involve, to a similar extent, both A and B genomes; relative total length of the latter seems to be increased in actual tetraploid wheat by comparison with the presumed original amphiploid. 4) Large structural differences, without affecting the ability of each chromosome to substitute the function of the homoeologous one, originated during the evolution of tetraploid Triticum species. This fact could be explained by exchanges involving mainly homoeologous chromosomes. 5) Such exchanges should be related to the presence of homoeologous pairing which is normally observed in our artificial amphiploid or noted in polyploid wheats in the case of repression or absence of the factor(s) controlling homologous pairing located in chromosome 5B. The authors conclude that an exchange of chromosome segments between homoeologous chromosomes in hybrids or amphiploids, before the occurrence of the mutation restricting the pairing to homologous chromosomes, probably played an essential role in wheat speciation.
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Claims 8
Claim · model-written summary
T. boeoticum and Ae. speltoides chromosomes differ morphologically from T. turgidum.
- Taxon
- T. boeoticum
Triticum monococcum subsp. aegilopoidese0 - Outcome
- Chromosome morphologye0
- Direction
- clearly differente0
- Comparator
- T. turgidume0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Chromosome morphology of T. boeoticum and Ae. speltoides is clearly different from that presented by T. turgidum.”
Claim · model-written summary
The chromosome morphology distinction from T. timopheevi is weaker.
Verbatim
e0“A similar distinction — even if at a lower degree — was found in respect to T. timopheevi.”
Claim · model-written summary
Chromosome morphology differentiation involves A and B genomes similarly.
TriticumOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Morphology differentiation of chromosome seems to involve, to a similar extent, both A and B genomes”
t0“Evolution of Tetraploid Wheats”
Claim · model-written summary
The B genome has greater relative total length in extant tetraploid wheat than in the presumed original amphiploid.
Verbatim
e0“relative total length of the latter seems to be increased in actual tetraploid wheat by comparison with the presumed original amphiploid.”
Claim · model-written summary
Large chromosome structural differences arose during tetraploid Triticum evolution without loss of homoeologous substitution ability.
- Outcome
- Large structural differencese0
- Qualifier
- without affecting the ability of each chromosome to substitute the function of the homoeologous onee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Large structural differences, without affecting the ability of each chromosome to substitute the function of the homoeologous one, originated during the evolution of tetraploid Triticum species.”
Claim · model-written summary
Homoeologous chromosome exchanges may explain the structural differences.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This fact could be explained by exchanges involving mainly homoeologous chromosomes.”
t0“Evolution of Tetraploid Wheats”
Claim · model-written summary
Homoeologous pairing is normally observed in the artificial amphiploid.
- Outcome
- homoeologous pairinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“homoeologous pairing which is normally observed in our artificial amphiploid”
t0“Evolution of Tetraploid Wheats”
Claim · model-written summary
Chromosome segment exchange before pairing restriction probably had an essential role in wheat speciation.
- Taxon
- wheat
Triticum aestivume0 - Outcome
- wheat speciatione0
- Qualifier
- an exchange of chromosome segments between homoeologous chromosomese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“an exchange of chromosome segments between homoeologous chromosomes in hybrids or amphiploids, before the occurrence of the mutation restricting the pairing to homologous chromosomes, probably played an essential role in wheat speciation.”