Development of a Fertility Restorer for inap CMS (Isatis indigotica) Brassica napus Through Genetic Introgression of One Alien Addition.

Pengfei Li,Aifan Wang,Xianhong Ge,Cheng Cui,Liangcai Jiang,Shizhen Guo,Lei Kang,Zaiyun Li

doi:10.3389/fpls.2019.00257

Abstract

Novel Brassica napus cytoplasmic male sterility (CMS) with carpelloid stamens (inap CMS) was produced by intertribal somatic hybridization with Isatis indigotica (Chinese woad), but its RF (restorer of fertility) gene(s) existed in one particular woad chromosome that was carried by one fertile monosomic alien addition line (MAAL) of rapeseed. Herein, the selfed progenies of this MAAL were extensively selected and analyzed to screen the rapeseed-type plants (2n = 38) with good male fertility and to produce their doubled haploid (DH) lines by microspore culture. From the investigation of fertility restoration in the F1 hybrids with inap CMS, one DH line (RF 39) was identified to adequately restore male fertility and likely carried one dominant RF gene. Specifically, this restorer produced brown pollen grains, similar to the woad and the MAAL, suggesting that this trait is closely linked with the RF gene(s) and serves as one phenotypic marker for the restorer. This restorer contained 38 chromosomes of rapeseed and no intact chromosomes of woad, but some DNA fragments of woad origin were detected at low frequency. This restorer was much improved for pollen and seed fertility and for low glucosinolate content. The successful breeding of the restorer for inap CMS rendered this new pollination control system feasible for rapeseed hybrid production.

Highlights

Male sterility in plants can be caused either by mitochondrial genes coupled with nuclear genes or by nuclear genes alone, known as cytoplasmic male sterility (CMS) and genic male sterility (GMS), respectively (Chen and Liu, 2014)
As only one B. napus-I. indigotica monosomic alien addition line (MAAL) (Me) among all seven MAALs had normal flowers with brown anthers, as did I. indigotica (Kang et al, 2014), its progenies by self-pollination from three generations were screened for plants with high pollen fertility and with the same 2n = 38 as B. napus during 2012– 2014 in Wuhan, Hubei Province and Xining, Qinghai Province
60 plants were primarily selected by their larger flowers and larger anthers, compared with MAAL Me, but showed variable seed-sets from low to high, likely because they had shorter and thinner stamens with low pollen fertility compared to the maintainer line (H3)

Summary

Introduction

Male sterility in plants can be caused either by mitochondrial genes coupled with nuclear genes or by nuclear genes alone, known as cytoplasmic male sterility (CMS) and genic male sterility (GMS), respectively (Chen and Liu, 2014). As Brassica coenospecies provide rich and diverse mitochondrial genomes (Pradhan et al, 1992), alloplasmy CMS lines have been developed following backcrossing of either sexually synthesized allopolyploids or somatic hybrids between wild and crop species to diversify the CMS sources for breeding (For review see Prakash et al, 2009). Only Ogura-INRA B. napus CMS (Friedt et al, 2018) and Mori B. juncea CMS, produced from somatic fusion with Moricandia arvensis (Singh, 2008), were successfully exploited for commercial seed production on a large scale after systematic improvement of developmental abnormalities, including leaf chlorosis (Pelletier et al, 1983; Kirti et al, 1998)

Methods

Results

Discussion

Conclusion