Backcross Compatibility in Hybrids between Brassicoraphanus (Brassica oleracea X Raphanus sativus) and Cruciferous Crops, and Clubroot Resistance in Their BC, Plants

All the F_1 hybrids between Brassicoruphunus ‘K-11’ and cruciferous crops showed very low pollen and seed fertility. Backcrossings of the F_1 hybrids with Raphunus sutiws and Brassica campestnk each were successful, whereas those with B. oleracea were almost unsuccessful under natural conditions. BC_1 plants could be obtained through embryo culture when F, hybrids were backcrossed with B. oleracea. In the backcrossings with R. sativus and B. campestris each, seed fertility was improved as the backcross generation and selection of the plants advanced. One to three trivalents were observed in the PMCs of BC_1 plants obtained by backcrossing F_1 hybrids with B. campestris. Clubroot resistant plants were obtained from BC, progenies derived from backcrossing of the BC_1 hybrids with R. sativus and B. campestnk each