Production of intergeneric hybrids between the C3-C4 intermediate species Diplotaxis tenuifolia (L.) DC. and Raphanus sativus L

In intergeneric crossings between Diplotaxis tenuifolia (2n=22,DtDt) and five cultivars of Raphanus sativus (2n=18,RR), an intergeneric F1 hybrid was produced from the crossing of D. tenuifolia*R. sativus cv.'4-season leaf' through ovary culture followed by embryo culture. The induced amphidiploid (2n=40, DtDtRR) showed well-regulated meiotic features at PMCs and a high pollen fertility (75%). Three BC1 hybrids with DtRR (2n=29) or DtDtR (2n=31) genome constitutions were obtained by the same embryo rescue procedure in the crossings of amphidiploid * R. sativus and D. tenuifolia * amphidiploid, respectively. In the successive backcrossings of two BC1 hybrids (DtRR, 2n=29) to R. sativus, 102 BC2 hybrids were obtained by conventional pollination. In the reciprocal crossing of R. sativus * BC1 hybrids, 12 reciprocal BC2 hybrids were also produced without embryo rescue. The somatic chromosome number of 89 BC2 hybrids with D. tenuifolia cytoplasm and 12 reciprocal BC2 hybrids with R. sativus cytoplasm ranged from 2n=18 to 2n=23 that were estimated to carry 2n=18 chromosomes of R. sativus and zero to five chromosomes of D. tenuifolia. Among them, 24.7% of the BC2 hybrids and 41.6% of the reciprocal BC2 hybrids were assumed to be monosomic addition lines (MALs, 2n=19). The novel intergeneric hybrids obtained in this study could become useful materials for investigating the genetic effects on C3-C4 intermediate traits at the genomic and chromosomal levels, as well as for estimating the performance of genetic improvement in Brassicaceae.