Quantitative trait locus analysis of heterosis for plant height and ear height in an elite maize hybrid zhengdan 958 by design III

Abstract

Background: Plant height (PH) and ear height (EH) are two important agronomic traits in maize selection breeding. F₁ hybrid exhibit significant heterosis for PH and EH as compared to their parental inbred lines. To understand the genetic basis of heterosis controlling PH and EH, we conducted quantitative trait locus (QTL) analysis using a recombinant inbreed line (RIL) based design III population derived from the elite maize hybrid Zhengdan 958 in five environments.

Results: A total of 14 environmentally stable QTLs were identified, and the number of QTLs for Z₁ and Z₂ populations was six and eight, respectively. Notably, all the eight environmentally stable QTLs for Z₂ were characterized by overdominance effect (OD), suggesting that overdominant QTLs were the most important contributors to heterosis for PH and EH. Furthermore, 14 environmentally stable QTLs were anchored on six genomic regions, among which four are trait-specific QTLs, suggesting that the genetic basis for PH and EH is partially different. Additionally, qPH.A-1.3, modifying about 10 centimeters of PH, was further validated in backcross populations.

Conclusions: The genetic basis for PH and EH is partially different, and overdominant QTLs are important factors for heterosis of PH and EH. A major QTL qPH.A-1.3 may be a desired target for genetic improvement of maize plant height.

Keywords: Design III; Ear height; Heterosis; Maize; Plant height.

Fig. 1

Experimental flow chat for QTL analysis and validation. The crossed of 162 RILs to their parental lines Zheng 58 (TC Zheng 58) and Chang 7–2 (TC Chang 7–2) were phenotyped for further QTL analysis. A major QTL, qPH.A-1.3 was validated using BC₂F_1, BC₃F₁ and BC₂F₂ populations

Fig. 2

Genetic locations of the 14 environmentally stable QTLs for PH and EH. The centiMorgan (cM) scale is shown on the left. Black ellipses indicate the approximate positions of the centromeres. Vertical bars in black represent the confidence interval of each QTL. A black vertical bar with black triangle represents heterotic-related QTLs detected for Z₂; a black vertical bar with a red triangle represents additive QTLs with positive alleles from parent Chang 7–2. Double-headed arrows represent the genomic regions characterized by QTL or QTL clusters. Red shadows on the physical map indicate the corresponding positions of each QTL. The verticals in different colors alongside the physical map indicate known heterotic-related QTLs from different studies (1 Ku et al. [43]; 2 Wen et al. [48]; 3 Yang et al. [45]; 4 Wang et al. [18]; 5 Frascaroli et al. [46]; 6 Song et al. [22]; 7 Frascaroli et al. [23]; 8 Li et al. [16]). The known positions of br2, an1, brd1, d8,d9, td1, clt1and d3 are presented in blue arrows

Fig. 3

Validation of qPH.A-1.3 for plant height (PH) in a: BC₂F₁ population, b: BC₂F₂ population, c: BC₃F₁ population. The three populations were genotyped by using the SSR markers MPH72 and MPH1149. The distributions and mean values for PH are shown as different genotypic classes: Z/Z homozygous for Zheng 58 haplotype, C/C homozygous for Chang 7–2 haplotype, or Z/C for heterozygous