Genetic architecture of male fertility restoration in a hybrid breeding system of rye (Secale cereale L.)

Abstract

The ‘Gülzow’ (G) type cytoplasmic male sterility (CMS) system in hybrid rye (Secale cereale L.) breeding exhibits a strong and environmentally stable restoration of male fertility (Rf). While having received little scientific attention, three G-type Rf genes had been identified on 4RL (Rfg1) and two minor genes on 3R (Rfg2) and 6R (Rfg3) chromosome. Here, we report a comprehensive investigation of the genetics underlying restoration of male fertility in a large G-type CMS breeding system using a palette of complementing forward and reverse genetic analysis. This includes (i) genome wide association studies (GWAS) on a G-type germplasm, (ii) GWAS on a biparental mapping population, (iii) in silico identification of Rf-like pentatricopeptide repeat (RFL-PPR) genes and their expressed in G-type rye hybrids, and (iv) mining patterns in linkage disequilibrium. Our findings provide compelling evidence of a novel major G-type non-PPR Rf gene on the 3RL chromosome. In the in silico analysis, we identified 22 RFL-PPR of which 15 were expressed in the transcriptome of G-type hybrids. Our findings provides a novel insight into the underlying genetics of male fertility restoration in a G-type CMS system in rye. The discovery made in this study is distinct to known P- and C-type systems in rye in addition to known CMS systems in barley and wheat. This study constitutes a steppingstone towards understanding the restoration of male fertility in G-type CMS system and a potential resources for addressing the inherent issues of the P-type system.

Ergot Alkaloid Contents in Hybrid Rye are Reduced by Breeding

“…The high preponderance of the male GCA variance for ergot severity illustrates that it is promising to reduce ergot susceptibility in hybrid rye by breeding for high pollen shedding, e.g., by introgressing non-adapted Rf genes [9] or by using alternative CMS cytoplasms that are easier to restore [36]. However, when a high pollen shedding is integrated in all rye hybrid breeding programs, the only way to make further achievements in reducing ergot towards the low percentages known from wheat is an additional resistance of the female parent for which first indications have been shown in this study and elsewhere [15,37].…”