Izhar Hussain, Sajid Ali,
Wuge Liu, Muhammad Awais, Jinhua Li, Yilong Liao, Manshan Zhu, Chongyun Fu,
Dilin Liu* and Feng Wang*

Frontiers
in Genetics

Abstract

Identification of the right parental combinations to maximize
heterosis is the major goal of hybrid breeding, which could be achieved through
identification of heterotic groups. The main objective of this study was to
identify promising heterotic groups for future rice breeding programs. A
collection of 359 rice genotypes of diverse origins of China and abroad,
composed of inbreds, maintainers, restorers, and temperature-sensitive genic
male sterile (TGMS) lines were genotyped using 10K SNP chips. The SNP data set
was subjected to genomic analyses for estimation of genetic divergence and
diversity. Significant variations were observed in the germplasm with the
identification of six different genetic groups. These lines were assigned to
the genetic groups independent of their origin. Taking an account of
commercially used heterotic groups present in each cluster, three cytoplasmic
male sterile (CMS) lines and 14 inbred and restorer lines with moderate to high
genetic distances selected from five heterotic patterns were crossed and
obtained 42 F1 hybrids. A total of 14 hybrids were found
with significant maximum mid- and better-parent heterosis, namely, TaifengA ×
Guang122, TaifengA × Wushansimiao, and TaifengA × Minghui63 for earliness;
Guang8A × Huazhan for dwarf stature; and Guang8A × Huanghuzhan-1, TaifengA ×
Yuexiangzhan, Guang8A × Minhui3301, TianfengA × Guang122, Guang8A × Yahui2115,
TianfengA × Huanghuazhan, TianfengA × Minghui63, TianfengA × Minhui3301,
TaifengA × Gui99, and Guang8A × Yuenongsimiao for yield and yield-related
traits. Mid-parent and better-parent heterotic F1 hybrids were in positive
correlation with the genetic distances as that manifested by commercially used
heterotic groups, encouraging the use of genotypic data for identification of heterotic
groups. Our study provides an informative strategy for the development of early
maturing, lodging resistant and high-yielding commercial hybrids and cultivars
in future heterosis breeding programs.

Keywords: heterotic groups, heterotic patterns, hybrid rice, SNP,
accession, genetic distance

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