GENETIC-ASPECTS OF HYBRID EMBRYO ABORTION IN THE GENUS LENS L

Hybrid embryo abortion is an effective crossing barrier in the genus L ens L. It divides the genus into two crossing groups: the Culinaris an d the Nigricans groups; but it is also evolving within the Culinaris g roup. The abortion of the F-1 embryo is strongly affected by dominant gene action. In the segregating generations embryo abortion is of a qu antitative nature and has both components, dominant and additive. Thes e were expressed differentially in the Lens ervoines x L. culinaris an d L. orientalis x L. culinaris cross combinations. The genetic control of embryo abortion was indicated further by the association between m arker loci and embryo abortion rates in segregating generations. Embry o abortion was not associated with chromosomal aberrations. The establ ishment of an embryo abortion reproductive barrier by a single somatic mutation in a locus affecting seed development is proposed as a first step in a build-up of genetic isolation in the genus Lens.