Abstract

Interspecific reciprocal crosses between three cultivated Brassica allotetraploidsand one wild species Brassica fruticulosa (FF, 2n =16) were made and the trigenomic hybrids were produced only with embryo rescue. From the crosses withBrassica juncea (AABB, 2n = 36) and Brassica napus (AACC, 2n = 38), hybrids (F.AB, 2n = 26; F.AC, 2n = 27) were obtained only with B. fruticulosa as female, but the reciprocal crosses with Brassica carinata (BBCC, 2n = 34) gave rise to hybrids (F.BC/BC.F, 2n = 25). These hybrids showed an intermediate morphology and were sterile for male and female except those with B. carinata. All the triploids showed high frequency of bivalents during diakinesis and metaphase I (MI) of meiosis. The allohexaploids (FF.AABB, 2n = 52; FF.AACC, 2n = 54; BBCC.FF, 2n = 50) were synthesized by colchicine treatments of respective hybrids in vitro, which showed growth vigor and had larger stature than the hybrids, but were male sterile except one (FF.AABB). They produced progenies with the expected chromosome complements (F.AABB, 2n = 44; F.AACC, 2n = 46; BBCC.F, 2n = 42) after pollination by respective Brassica allotetraploids. In these allohexaploids, chromosomes were mainly paired as bivalents at diakinesis and segregated equally at anaphase I (AI) during meiosis of pollen mother cells (PMCs). These allohexaploids and progenies were valuable for the breeding of Brassica crops.

Key words: Brassica allotetraploids, Brassica fruticulosa, interspecific hybrids, crossability, morphology, genomic affinity.

Abbreviation

PMCs, Pollen mother cells; MI, metaphase I; AI/TI, anaphase I/telophase I; GISH, genomic in situ hybridization; DAPI, 4’-6-diamidino-2-phenylindole.