Abstract
Hybrid breeding is of economic importance in agriculture for increasing yield, yet the basis of heterosis is not well understood. In Arabidopsis, crosses between different accessions produce hybrids with different levels of heterosis relative to parental phenotypes in biomass. In all hybrids, the advantage of the F1 hybrid in both phenotypic uniformity and yield gain is lost in the heterogeneous F2. F5/F6 Hybrid Mimics generated from a cross between C24 and Landsberg erecta (Ler) ecotypes demonstrated that the large plant phenotype of the F1 hybrids can be stabilized. Hybrid Mimic selection was applied to Wassilewskija (Ws)/Ler and Col/Ler hybrids. The two hybrids show different levels of heterosis. The Col/Ler hybrid generated F7 Hybrid Mimics with rosette diameter and fresh weight equivalent to the F1 hybrid at 30 DAS; F7 Ws/Ler Hybrid Mimics outperformed the F1 hybrid in both the rosette size and biomass. Transcriptome analysis revealed up‐regulation of cell wall biosynthesis, and cell wall expansion genes could be a common pathway in increased size in the Arabidopsis hybrids and Hybrid Mimics. Intercross of two independent Hybrid Mimic lines can further increase the biomass gain. Our results encourage the use of Hybrid Mimics for breeding and for investigating the molecular basis of heterosis.
Highlights
Hybrids have proved to have great value in agriculture as they pro‐ duce large gains in biomass and seed yield in a number of crops (Cheng, Zhuang, Fan, Du, & Cao, 2007; Crow, 1998; Dan et al, 2014)
We found that apart from CesA10 which was expressed at a low level in leaf tis‐ sue, all nine other cellulose synthase (CesA) genes (CesA1‐9) were significantly up‐regu‐ lated or showed a trend of up‐regulation in the Ws/Landsberg erecta (Ler) hybrids and the seven Hybrid Mimics (Figure 4a,b)
The fresh weight of intercross offspring was increased by 20% compared with the better parental Hybrid Mimic and was 30% greater than the Ler × Ws F1 hybrid, and comparable to Ler × Col F1 (Figure 7a–c)
Summary
Hybrids have proved to have great value in agriculture as they pro‐ duce large gains in biomass and seed yield in a number of crops (Cheng, Zhuang, Fan, Du, & Cao, 2007; Crow, 1998; Dan et al, 2014). We selfed F2 individuals and coupled these crosses with selection based on the phenotype of the F1 hybrid These procedures, repeated in successive generations gave, in the F6 and later generations, lines with rosette diameter, biomass, and seed yield comparable to the F1 hybrid (Wang et al, 2015, 2017). The interactions of the two paren‐ tal genomes in the F1 hybrid set the level of hybrid vigor that could be achieved by the component alleles of the parents through levels of gene expression and interactions between sequences in the two parental genomes These Hybrid Mimics overcame the F1/F2 hurdle, providing a seed source for high yielding crops based on kept‐seed planting. Selection for high‐performing Hybrid Mimics and intercrossing of different Mimic lines could be methods for breed‐ ing high biomass plants
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