Caractère << aberrant >>chez le chou-fleur(Brassica oleracea L.var.Bortrytis)

Abstract

Since 10 years, studies of aberrant plants in cauliflower have been performed to identify their origin. We try to find the common characters to the numerous phenotypes of the aberration. The reversibility and the non mendelian transmission of the plant perturbations suggested an epigenetic phenomenon. First analysis showed a DNA méthylation polymorphism and, in some of them, a variation of the DNA quantity, with one or two more chromosomes, and even with the loss of DNA. To estimate tire link of aberration to aneuploidy for two varieties, Neven and Nominoé, several methods of cytogenetical analysis have been associated to establish the reliability and the precision of the data obtained by flow cytometry. Only, the plants presented a loss of DNA (-5.8% to -2.5%) have not been observed at mitotic or meiotic stages because of their great development perturbations. The type of aneuploidy could vary for the same plant during its development, and the rate of aneuploids was different from one variety to another during the different stages of the development. The modifications of the DNA quantity have not always been link to morphological variations. Partial data of the rate methylated cytosine have been obtained by HPLC measures. These data would indicate a hyperméthylation of the aberrant plant DNA. Nevertheless, the method still needs to be improved for cauliflower. For the study of the systemic transmission of the aberration or the reversion to normality, a grafting experience allowed to show interactions between scion and stock, and in the two ways, either they were normal or aberrant, contrary to the known systemic transmission of gene silencing .