Genetic mapping of pollen fertility restoration QTLs in rye (Secale cereale L.) with CMS Pampa

Agnieszka Niedziela,Waldemar Brukwiński,Piotr Tomasz Bednarek

doi:10.1007/s13353-020-00599-9

Abstract

Cytoplasmic male sterility (CMS) is a widely applied plant breeding tool for hybrid seed production. The phenomenon is often caused by chimeric genes with altered open reading frames (ORFs) located in the mitochondrial genomes and expressed as novel genotoxic products that induce pollen abortion. The fertility of CMS plants can be restored by nuclear-encoded genes that inhibit the action of ORFs responsible for pollen sterility. A recombinant inbred line (RIL) mapping population S64/04/01, encompassing 175 individuals, was used for genetic map construction and identification of quantitative trait loci (QTLs) responsible for fertility restoration in rye (Secale cereale L.) with CMS Pampa. The genetic map of all seven rye chromosomes included 15,516 SNP and silicoDArT markers and covered 1070.5 cm. Individual QTLs explaining 60% and 5.5% of the fertility trait’s phenotypic variance were mapped to chromosomes 4R (QRft-4R) and 5R (QRft-5R), respectively. Association mapping identified markers with the highest R2 value of 0.58 (p value = 2.21E-28). Markers showing the highest associations with the trait were also mapped to the 4R chromosome within the QRft-4R region. Based on marker sequence homology, putative genes involved in pollen fertility restoration were suggested. Five silicoDArTs were converted into PCR-based markers for further breeding purposes.

Highlights

Cultivated rye (Secale cereale L.) is a cross-pollinated, diploid (2n = 14) cereal with seven pairs of chromosomes
Fertile plants were present in a low number (6 plants: 5–6 score according to the bonitation scale) and, due to the presence of pollen, were included into the fertile class in the segregation analysis
The observed data may be explained in several ways: (1) The distortion is due to the lack of phenotypic data of the 30 missing genotypes; (2) phenotyping was performed in a single environment without repeats; and (3) the analyzed population has several Quantitative trait loci (QTL) conferring pollen fertility restoration traits in the rye

Summary

Introduction

Cultivated rye (Secale cereale L.) is a cross-pollinated, diploid (2n = 14) cereal with seven pairs of chromosomes. Rye breeding efforts are focused on improving grain yield as the most crucial objective. Hybrid rye varieties give 10–20% higher yields than open-pollinated varieties grown under the same agrotechnical conditions. One of the most exploited hybrid breeding systems in rye Communicated by: Izabela Pawłowicz. Restoration of pollen production in sterile plants, including rye hybrids, requires a male parent (pollinator) that holds effective pollen fertility restoration (Rf) nuclear genes. Male fertility restoration genes for the Pampa cytoplasm appear in less than 5% of European rye materials, with effectiveness in the 2–74% range (Miedaner et al 2005). The activities of these genes may be dependent on the environmental conditions present before and during flowering (Geiger and Miedaner 1996). Lack of pollen and the resulting presence of young, unfertilized ovaries facilitate infection by the ergot fungus Claviceps purpurea, which replaces the seeds with dark mycelial masses sclerotia

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Conclusion