Developmentally aberrant plants in F1 hybrids of Brassica oleracea.

Over the last fifty years, Fl hybrids have been developed to improve the homogeneity of Brassica crops. In these varieties, male sterility (mainly CMS) allows the production of 100% hybrid seed. Nonetheless, under field conditions, we observed aberrant plants that were unsuitable for harvest in Fl hybrid crops. The phenotypes of these plants principally involve the modification of three characters: leaf shape, size and thickness. We observed similar developmental perturbations in a range of different cultivars (hybrids, lines and populations). Between 5% and 21% aberrant plants were observed in crops of the same hybrid observed over a four year period. We were not able to identify agronomic parameters (seed origin, period of planting, locality) that could be correlated with the frequency of aberrant plants. The response of aberrant plants to in vitro propagation was variable, either remaining aberrant, altering their phenotype or recovering a normal phenotype. Analysis of ploidy levels by flow cytometry did not reveal any abnormalities linked to the observed phenotypes. Inheritance of the aberrant phenotypes was variable. The progenies obtained by selfing abet-rant plants included (i) families of 100% normal plants, (ii) families showing Mendelian segregation of the phenotype, (iii) mixtures of aberrant plants with numerous phenotypes and normal plants, and (iv) families of 100% aberrant plants. Further studies have been conducted to identify agronomic factors that favour the appearance of aberrant phenotypes and to understand the underlying genetic mechanism. The susceptibility of different genetic backgrounds to the development of aberrant phenotypes will also be considered.