Abstract
SummaryHeterosis, or hybrid vigour, is a predominant phenomenon in plant genetics, serving as the basis of crop hybrid breeding, but the causative loci and genes underlying heterosis remain unclear in many crops. Here, we present a large‐scale genetic analysis using 5360 offsprings from three elite maize hybrids, which identifies 628 loci underlying 19 yield‐related traits with relatively high mapping resolutions. Heterotic pattern investigations of the 628 loci show that numerous loci, mostly with complete–incomplete dominance (the major one) or overdominance effects (the secondary one) for heterozygous genotypes and nearly equal proportion of advantageous alleles from both parental lines, are the major causes of strong heterosis in these hybrids. Follow‐up studies for 17 heterotic loci in an independent experiment using 2225 F2 individuals suggest most heterotic effects are roughly stable between environments with a small variation. Candidate gene analysis for one major heterotic locus (ub3) in maize implies that there may exist some common genes contributing to crop heterosis. These results provide a community resource for genetics studies in maize and new implications for heterosis in plants.
Highlights
Heterosis, or known as hybrid vigour, refers to the phenomenon where the F1 hybrid has greater phenotypic performance than both inbred parents (Bruce, 1910; East, 1936; Jones, 1917; Shull, 1908)
Another hybrid Siyu-2 from the C428 9 C434 cross is a newly developed maize cultivar in China, and the parental line C434 is derived from Chang7-2 in breeding
There were totally 6 807 279 SNPs, 5 285 206 SNPs and 4 094 055 SNPs across the maize genome (AGPv4). These SNPs between parents covered the majority of genomic regions, facilitating follow-up genotyping in the F2 populations (Figure S1a-c)
Summary
Known as hybrid vigour, refers to the phenomenon where the F1 hybrid has greater phenotypic performance than both inbred parents (Bruce, 1910; East, 1936; Jones, 1917; Shull, 1908). In a number of plant species (e.g. Arabidopsis, rice, maize, sorghum and tomato), genetic mapping has been used to identify the detailed gene loci contributing to hybrid performances and investigate their mechanisms (Swanson-Wagner et al, 2006; Riedelsheimer et al, 2012; Zhou et al, 2012; Yao et al, 2013; Dapp et al, 2015; Birchler et al, 2016; Li et al, 2016; Yang et al, 2017a,b; Liu et al, 2019). In tomato and rice, the orthologue gene of Arabidopsis flowering locus SFT for tomato (Krieger et al, 2010) and Hd3a for rice (Huang et al, 2016), respectively, has been found to show single-gene overdominance In another case, repulsion linkage between two quantitative trait loci (QTLs) underlying plant height (qHT7.1 and Dw3) with dominance effects caused the occurrence of heterosis in sorghum (Li et al, 2015)
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