Properties of self-sterile but cross-fertile allopolyploids synthesized between Brassica rapa and Raphanus sativus

To expand the availability of intergeneric allopolyploids between Brassica rapa and Raphanus sativus beyond BB#1, a stable xBrassicoraphanus koranhort (baemoochae) cultivar (2n = 38, aAARR genome), we developed four intergeneric hybrids between different materials from B. rapa and R. sativus. These hybrids produced neither self-pollinated seeds nor embryos in microspore culture. The hybrids, however, did produce seeds (F1F1) via cross-pollination with existing baemoochae and mooyangchae, another xBrassicoraphanus line (2n = 36, rCCRR genome) generated from a cross between R. sativus and B. oleracea at Huazhong Agriculture University, China. The hybrid plants (F1F1) produced more seeds than the previous generation in both self- and cross-pollination and embryos, even in the presence of an induced microspore mutation. The self-sterile, cross-fertile properties of the newly synthesized allopolyploids suggest possible mechanisms for fertility restoration and provide valuable information for the development of intergeneric baemoochae cultivars.