Breeding by design of CMS lines on the platform of SSSL library in rice

Abstract

Greatly increased yield by utilizing of heterosis has been a great success in rice over the past 40 years. The cytoplasmic male sterility (CMS) line is a key line of hybrid rice. However, the CMS line was very difficult to develop following the traditional breeding methods. Here, we report an example to develop and improve CMS lines sustainably by using the strategy of breeding by design under the platform of single segment substitution line (SSSL) library in the Huajingxian74 (HJX74) genetic background. The CMS lines HZA and HBA with the wild abortive (WA) cytoplasm from Zhenshan97A and BobaiA, respectively, were firstly developed in the HJX74 background through markerassisted selection. Then, four isonuclear alloplasmic CMS lines with the WA, dwarf wild abortive (DA), and Yegong abortive (YA) types of CMS cytoplasm, respectively, were developed by using the HZB maintainer line. According to the goal of design, E5-HXA and E5-HBA were developed by pyramiding five target genes, Wx g1 , ALK, fgr, gs3, and OsMADS50, located on the chromosomal substituted segments in four SSSLs. The two CMS lines show the phenotypes of earlier in heading date, longer and narrower in grain shape, lower in amylose content, and fragrant smell. Thus, the goal of design was achieved on the platform of SSSL library. Compared with that in the E5-HXA line carrying the rf3 and rf4 genes of XieqingzaoA, the CMS in the E5-HBA line with the rf3 and rf4 genes from BobaiA was susceptible to environmental impact and easy to be restored. Therefore, the balance between sterility and its restored ability in CMS lines should be concerned in breeding by design.

The Next Generation of Rice: Inter-Subspecific Indica-Japonica Hybrid Rice

“…The HJX74-SSSLs have been used to detect QTLs for complex traits ( Zhang et al, 2012 ; Yang et al, 2016 , 2021a , 2021b ; Zhou et al, 2017 ; Tan et al, 2020 , 2021 , 2022 ; Pan et al, 2021 ), to clone genes of agronomic importance and to assess allelic variation ( Wang et al, 2008 , 2012 , 2015 ; Teng et al, 2012 ; Sui et al, 2019 ; Zhang et al, 2020 ; Gao et al, 2021 ). Using the HJX74-SSSL library as platform for rice breeding by design, several CMS, maintainer and restorer lines have been developed ( Dai et al, 2015 , 2016 ; Luan et al, 2019 ). These results suggest that the target chromosome-segment substitution is an effective way to rice breeding by design ( Zhang, 2021 ).…”

Dissection of closely linked QTLs controlling stigma exsertion rate in rice by substitution mapping

“…Based on the HJX74-SSSL library, the platform of breeding by design in rice has been developed (Dai et al 2015 , 2016 ; Luan et al 2019 ; Zhang 2019 ). In this study, we found that the qSER-2a and qSER-2b on chromosome 2 and the qSER-3a and qSER-3b on chromosome 3 had significant additive effects for SER.…”

GW10, a Member of P450 Subfamily Regulates Grain Size and Grain Number in Rice

“…It was difficult to determine the precise location of QTLs in rice genome by using the F2 plants, Recombinant Inbred Lines (RILs), Backcross Inbred Lines (BILs) and Doubled Haploid Lines (DHLs) (Ashikari et al 2006). Consequently, the development of Nearly Isogenic Lines (NILs), Chromosome Fragment Substitution Line (CSSL) and Single Segment Substitution Line (SSSL) were necessary for QTL fine mapping and gene cloning (Ashikari et al 2006;Guo et al 2016;Zhou et al2017;Wang et al 2018;Yang et al 2018;Luan et al 2019;Tan et al 2020;Tan et al 2021), especially for the minor genes.…”