Abstract：
Heterosis is widely used in agriculture. However, its molecular mechanisms are still unclear in plants. Here, we develop, sequence, and record the phenotypes of 418 hybrids from crosses between two testers and 265 rice varieties from a mini-core collection.
Phenotypic analysis shows that heterosis is dependent on genetic backgrounds and environments. By genome-wide association study of 418 hybrids and their parents, we find that nonadditive QTLs are the main genetic contributors to heterosis. We show that nonadditive QTLs are more sensitive to the genetic background and environment than additive ones. Further simulations and experimental analysis support a novel mechanism, homo-insufficiency under insufficient background (HoIIB), underlying heterosis. We propose heterosis in most cases is not due to heterozygote advantage but homozygote disadvantage under the insufficient genetic background.
The HoIIB model elucidates that genetic background insufficiency is the intrinsic mechanism of background dependence, and also the core mechanism of nonadditive effects and heterosis. This model can explain most known hypotheses and phenomena about heterosis, and thus provides a novel theory for hybrid rice breeding in future.
Phenotypic analysis shows that heterosis is dependent on genetic backgrounds and environments. By genome-wide association study of 418 hybrids and their parents, we find that nonadditive QTLs are the main genetic contributors to heterosis. We show that nonadditive QTLs are more sensitive to the genetic background and environment than additive ones. Further simulations and experimental analysis support a novel mechanism, homo-insufficiency under insufficient background (HoIIB), underlying heterosis. We propose heterosis in most cases is not due to heterozygote advantage but homozygote disadvantage under the insufficient genetic background.
The HoIIB model elucidates that genetic background insufficiency is the intrinsic mechanism of background dependence, and also the core mechanism of nonadditive effects and heterosis. This model can explain most known hypotheses and phenomena about heterosis, and thus provides a novel theory for hybrid rice breeding in future.
摘要：
背景：杂种优势在农业中被广泛使用。然而,其分子机制在植物中仍不清楚。这里,我们发展,序列,并记录来自两个测试人员之间杂交的418个杂种的表型，以及来自微型核心集合的265个水稻品种。
结果：表型分析表明，杂种优势取决于遗传背景和环境。通过对418个杂种及其亲本的全基因组关联研究，我们发现非加性QTL是杂种优势的主要遗传因素。我们表明，非加性QTL比加性QTL对遗传背景和环境更敏感。进一步的模拟和实验分析支持一种新颖的机制，不足背景下的同质不足(HoIIB)，潜在的杂种优势。我们认为，在大多数情况下，杂种优势不是由于杂合子的优势，而是由于遗传背景不足的纯合子的劣势。
结论：HoIIB模型阐明了遗传背景不足是背景依赖的内在机制，以及非加性效应和杂种优势的核心机制。这个模型可以解释大多数已知的关于杂种优势的假设和现象，为今后杂交水稻育种提供了新的理论依据。
结果：表型分析表明，杂种优势取决于遗传背景和环境。通过对418个杂种及其亲本的全基因组关联研究，我们发现非加性QTL是杂种优势的主要遗传因素。我们表明，非加性QTL比加性QTL对遗传背景和环境更敏感。进一步的模拟和实验分析支持一种新颖的机制，不足背景下的同质不足(HoIIB)，潜在的杂种优势。我们认为，在大多数情况下，杂种优势不是由于杂合子的优势，而是由于遗传背景不足的纯合子的劣势。
结论：HoIIB模型阐明了遗传背景不足是背景依赖的内在机制，以及非加性效应和杂种优势的核心机制。这个模型可以解释大多数已知的关于杂种优势的假设和现象，为今后杂交水稻育种提供了新的理论依据。
