title: Genetic composition of yield heterosis in an elite rice hybrid.
abstract: Heterosis refers to the superior performance of hybrids relative to the parents. Utilization of heterosis has contributed tremendously to the increased productivity in many crops for decades. Although there have been a range of studies on various aspects of heterosis, the key to understanding the biological mechanisms of heterotic performance in crop hybrids is the genetic basis, much of which is still uncharacterized. In this study, we dissected the genetic composition of yield and yield component traits using data of replicated field trials of an "immortalized F(2)" population derived from an elite rice hybrid. On the basis of an ultrahigh-density SNP bin map constructed with population sequencing, we calculated single-locus and epistatic genetic effects in the whole genome and identified components pertaining to heterosis of the hybrid. The results showed that the relative contributions of the genetic components varied with traits. Overdominance/pseudo-overdominance is the most important contributor to heterosis of yield, number of grains per panicle, and grain weight. Dominance × dominance interaction is important for heterosis of tillers per plant and grain weight and has roles in yield and grain number. Single-locus dominance has relatively small contributions in all of the traits. The results suggest that cumulative effects of these components may adequately explain the genetic basis of heterosis in the hybrid.
authors.affiliation: National Key Laboratory of Crop Genetic Improvement and National Centre of Plant Gene Research (Wuhan),  Huazhong Agricultural University, Wuhan 430070,  China.
authors.forename: Gang
authors.initials: G
authors.lastname: Zhou
authors.forename: Ying
authors.initials: Y
authors.lastname: Chen
authors.forename: Wen
authors.initials: W
authors.lastname: Yao
authors.forename: Chengjun
authors.initials: C
authors.lastname: Zhang
authors.forename: Weibo
authors.initials: W
authors.lastname: Xie
authors.forename: Jinping
authors.initials: J
authors.lastname: Hua
authors.forename: Yongzhong
authors.initials: Y
authors.lastname: Xing
authors.forename: Jinghua
authors.initials: J
authors.lastname: Xiao
authors.forename: Qifa
authors.initials: Q
authors.lastname: Zhang
mesh_terms: D002678:Chimera / Q000235:genetics*; D005799:Genes, Dominant; D056426:Genetic Loci; D018745:Genome, Plant / Q000235:genetics*; D006823:Hybrid Vigor / Q000235:genetics*; D012275:Oryza / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide