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

Abstract

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 x 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 x R. sativus and D. tenuifolia x amphidiploid, respectively. In the successive backcrossings of two BC 1 hybrids (DtRR, 2n=29) to R. sativus, 102 BC2 hybrids were obtained by conventional pollination. In the reciprocal crossing of R. sativus x BC1 hybrids, 12 reciprocal BC2 hybrids were also produced without embryo rescue. The somatic chromosome number of 89 BC 2 hybrids with D. tenuifolia cytoplasm and 12 reciprocal BC 2 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.