Abstract
Early flowering facilitates crops to adapt multiple cropping systems or growing regions with a short frost-free season; however, it usually brings an obvious yield loss. In this study, we identified that the three genes, namely, BnFLC.A2, BnFLC.C2, and BnFLC.A3b, are the major determinants for the flowering time (FT) variation of two elite rapeseed (Brassica napus L.) accessions, i.e., 616A and R11. The early-flowering alleles (i.e., Bnflc.a2 and Bnflc.c2) and late-flowering allele (i.e., BnFLC.A3b) from R11 were introgressed into the recipient parent 616A through a breeding strategy of marker-assisted backcross, giving rise to eight homozygous near-isogenic lines (NILs) associated with these three loci and 19 NIL hybrids produced by the mutual crossing of these NILs. Phenotypic investigations showed that NILs displayed significant variations in both FT and plant yield (PY). Notably, genetic analysis indicated that BnFLC.A2, BnFLC.C2, and BnFLC.A3b have additive effects of 1.446, 1.365, and 1.361 g on PY, respectively, while their dominant effects reached 3.504, 2.991, and 3.284 g, respectively, indicating that the yield loss caused by early flowering can be successfully compensated by exploring the heterosis of FT genes in the hybrid NILs. Moreover, we further validated that the heterosis of FT genes in PY was also effective in non-NIL hybrids. The results demonstrate that the exploration of the potential heterosis underlying the FT genes can coordinate early flowering (maturation) and high yield in rapeseed (B. napus L.), providing an effective strategy for early flowering breeding in crops.
Highlights
Rapeseed (Brassica napus L.) is one of the most important oil crops worldwide and comprises more than 55% of the total oilseed production in China
What is the genetic reason that 616A has the early flowering phenotype in both the winter and spring environments?
The results showed that 616A carries the conserved WT alleles in both genes as reported before (Chen L. et al, 2018), which extremely significantly delayed the flowering in the double haploid (DH) population derived from the F1 cross between 616A and R11 (Supplementary Figures 1, 2)
Summary
Rapeseed (Brassica napus L.) is one of the most important oil crops worldwide and comprises more than 55% of the total oilseed production in China. With the change of cultivation systems for next-stubble crops (e.g., rice and corn) in central China, the growth season of rapeseed is being restricted. In northwestern China, undetermined early frost is often a threat to seed maturation. A shorter growing season or earlier maturation time would enable increased cultivation area and production for rapeseed in China. As flowering time (FT) is often associated with maturation time in crops (Wang Y. et al, 2021), the implementation of shorter growth stages via regulating FT becomes a feasible idea.
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