Factors limiting seed yield potential in F1 hybrids between natural and resynthesized Brassica napus

摘要

Resynthesized Brassica napus lines are of great potential in hybrid breeding for their higher genetic basis.An 8 × 8 complete diallel experiment was designed using 4 B.napus cultivars (BN) and 4 resynthesized rapeseed lines (RS) as parents,and all 56 F1 were divided into BN × BN,NR (RS × BN/BN × RS) and RS × RS types.Their heterosis for agronomic characteristics were investigated,especially on NR hybrids.Results showed that NR hybrids had higher plants,longer branches,more siliques and fewer seeds per silique at highly significant level when compared with conventional rapeseed cultivars.For yield per plant,all 32 NR cross combinations showed positive mid-parent heterosis and 25 ％ of the combinations (8 from 32 NRs) showed positive high-parental heterosis.On average of the 32 NRs,the heterosis was 30.56％ over mid-parents and-8.57％ over high-parents.Compared with BN × BN hybrids,NRs had more siliques per plant (437.0 vs 370.9) and fewer seeds per silique (11.6 vs 17.3).There was no significant difference on thousand seed weight between NR and BN × BN hybrids.NR hybrids showed abnormal flower organs,including A:59％ of NR combinations had more or less abnormal perianth or anthers;B:pollen fertility reduced,ranging from 56.2％ to 95.5％ and 80.7％ on average;C:poor silique-set (33.4％ on average) and seed set (7.8-+ 3.6 seeds per silique) after self -pollination;D:frequent univalents and muhivalents in metaphase I of meiosis;E:they showed highly significant self-incompatibility.