Tianzi Lin, Cong Zhou, Gaoming Chen, Jun Yu, Wei Wu, Yuwei Ge, Xiaolan Liu, Jin Li, Xingzhou Jiang, Weijie Tang, Yunlu Tian, Zhigang Zhao, Chengsong Zhu, Chunming Wang & Jianmin Wan

Theoretical and Applied Genetics December 2020; vol. 133:3287–3297.

Key message

Heterosis QTLs, including qSS7 and qHD8, with dominance effects were identified through GBS and large-scale phenotyping of CSSLs and hybrid F₁ populations in a paddy field.

Abstract

Heterosis has contributed immensely to agricultural production, but its genetic basis is unclear. We evaluated dominance effects by creating two hybrid populations: a B-homo set with a homozygous background and heterozygous chromosomal segments and a B-heter set with a heterozygous background and homozygous segments. This was achieved by crossing a set of 156 backcrossed-derived chromosome segment substitution lines (CSSLs) with their recurrent parent (9311), the male parent of the first super-high-yield hybrid Liangyoupei9 (LYP9), and with the female parent (PA64s) of the hybrid. The CSSLs were subjected to a genotyping-by-sequencing analysis to develop a genetic map of segments introduced from the PA64s. We evaluated the heterotic effects on eight yield-related traits in the hybrid variety and F₁ populations in large-scale field experiments over 2 years. Using a linkage map consisting of high-density SNPs, we identified heterosis-associated genes in LYP9. Five candidate genes contributed to the high yield of LYP9, with qSS7 and qHD8 repeatedly detected in both B-hybrid populations. The heterozygous segments harboring qSS7 and qHD8 showed dominance effects that contributed to the heterosis of yield components in the hybrid rice variety Liangyoupei9.

See: https://link.springer.com/article/10.1007/s00122-020-03669-y

Figure 2: QTLs detected on 12 chromosomes. A scale at the left side represents physical position (Mb). QTLs detected in the environment E1 were marked in orange, and QTLs in E2 were marked in green. Among these QTLs, qSS7 and qHD8 were identified repeatedly in the two hybrid sets in a homozygous background (a) and heterozygous background (b), respectively.