Articles
SOME INFORMATION ON THE PLUM CYTOGENETICS AND THE ORIGIN OF PRUNUS DOMESTICA
The cytological study of the three species, cerasifera, spinosa and domestica, allow us to have an idea upon chromosic homology between the species.
These relations of chromosomic homology were stated precisely by studying interspecific hybrids.
The study of triploid hybrids is very interesting and enabled us:
- to point out a very strong homology between two of the three genomes confronted in the hybrid but it was not possible to tell which of them;
- to make conspicuous the phenomenon of total cytomixis leading to unreduced gametes.
The study of tetraploid hybrids shows that Prunus cerasifera finds an homological genome in Prunus domestica but this can not give an evidence to Crane and Lawrence’s hypothesis.
The analysis of pentaploid hybrids (domestica x spinosa) gives evidence to the relations of homology between the confronted genomes but it was shown also that those hybrids produced with a not negligeable frequency gametes with n=24 identical to those of Prunus domestica if Crane and Lawrence’s hypothesis is right.
This allows to propose a breeding plateform aiming to introduce in Prunus domestica a character of the tetraploid specie P. spinosa.
From the classical genomic hypothesis flows two possible schemes for Prunus spinosa (SS1 or SC), the study of the triploid hybrids allows no choice.
From these two schemes, two hypotheses can be proposed, one of them is new: according to it spinosa is not present in domestica.
Other complementary cytological studies are necessary to choose the most probable hypothesis.
However, the first observations realised upon one of the two Rybine’s amphidiploids show a meiotoc behaviour rather different from that of Prunus domestica studied.
Accurate cytological basis seem to be useful as well as to carry on a breeding programme for Prunus domestica to create new rootstocks having pecular agronomical qualities.