SELECTION IN-VITRO FOR ERUCIC-ACID CONTENT IN SEGREGATING POPULATIONS OF MICROSPORE-DERIVED EMBRYOIDS OF BRASSICA-NAPUS

Microspore culture of Brassica napus under optimized conditions leads to the regeneration of microspore-derived embryoids that, at the late cotyledonary stage, contain large amounts of storage lipids, equal or similar in composition to those found in seeds of the homozygous donor plants. At that stage, the microspore-derived embryoids are large enough to allow the dissection of one cotyledon under aseptic conditions and the determination of its fatty-acid composition. The remaining part of the embryoid can be cultured further and regenerated to give a plant. This offers the possibility of early selection for fatty-acid composition in segregating populations of microspore-derived embryoids. In order to verify this hypothesis, embryoids were generated from microspores of F-1 plants derived from a cross between doubled haploid lines of the low-erucic-acid cv. 'Duplo' and the high-erucic-acid cv. 'Janetzki'. The contents of eicosenoic acid (C20:1) and erucic acid (C22:1) in the cotyledons and in the seeds derived from plants regenerated From the remaining parts of the embryoids were highly correlated (r(s) = 0.85** P = 0.01). This indicates that, in breeding programmes for high erucic acid, the majority of the microspore-derived embryoids can be discarded at an early stage in vitro. Only microspore-derived embryoids with a high content of C20: 1 + C22: 1 in the cotyledons need to be transferred to the greenhouse. This report also deals with the addition of abscisic acid (ABA) to the embryoid culture medium to increase the correlation, and discusses the possible application of this system for the selection of high-oleic or low-linolenic types in corresponding microspore-derived embryoid populations.