Meiotic Behaviour in the Brassiceae

Abstract

At meiosis in Brassica oleracea (cabbage and Brussels sprout), B. pekinensis and the related Sinapis arvensis and Eruca sativa, multivalents were common and numerous secondary associations of bivalents were detectable in all species from diplotene into metaphase. Quadrivalent formation in cabbage and Brussels sprouts usually involved an increase in chiasma frequency per cell and there is evidence that the potential quadrivalent frequency is limited, at least partly, by limited chiasma formation. Secondary associations are thought to represent lapsed multivalents. Extensive duplication of chromosomes (or of large chromosome segments), is therefore implied, and polysomic rather than diploid breeding behaviour should be expected for many gene loci.