Synthesis and fertility of Brassicoraphanus and ways of transferring Raphanus characters to Brassica

About 250 intergeneric hybrids with the genome constitution AR, AARR or ARR were obtained from over 15 000 crosses between Brassicacampestris (AA or AAAA, female parent) and Raphanussativus (RR or RRRR). The poor crossability was shown to be a consequence of various breeding barriers. The diploid and tetraploid hybrids were studied in form, fertility, chromosome association at meiosis and crossability both among the hybrids and in crosses with the parental species and Brassicanapus . x Brassicoraphanus (AARR) was backcrossed twice with B . campestris (AA), and was also crossed and backcrossed with B . napus (AACC). Form and chromosome association at meiosis in AAR and AACR hybrids were studied.Two populations of X Brassicoraphanus (AARR) were propagated and studied in more detail, partly for possible suitability as a new crop. Most plants were highly sterile because of breeding barriers, which were similar to those in the original intergeneric crosses. The increase in fertility and chromosomal stability were studied in the first three generations of the populations.