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ReproTag Résumé de rapport

Project ID: 631741
Financé au titre de: FP7-PEOPLE
Pays: Switzerland

Periodic Report Summary 1 - REPROTAG (ReproTag - Targeting reproductive traits for more efficient forage grass breeding)

Grassland is of high ecological and economic importance for Europe and contributes to sustainable feed and food production worldwide. Novel grass breeding schemes based on a more efficient exploitation of heterosis have the potential to substantially outperform current forage grass varieties in terms of biomass and seed yield, resistance and tolerance to biotic and abiotic stresses, respectively. However, current attempts to produce hybrids in forage crops have major limitations: Firstly, efficient production of inbred lines is hampered by self-incompatibility (SI), a genetic mechanism that efficiently promotes cross pollination, and secondly, tools to control pollination for efficient hybrid seed production are missing.
Therefore, the overall goal of the proposed research is to identify, characterize and utilize biological mechanisms in forage grasses to control pollination, which can – among a broad range of other applications – be exploited in hybrid breeding schemes. In particular, the proposed research focuses on the two-locus SI system, fertility restoring self-compatibility loci (SC), doubled haploid induction and male sterility mechanisms in perennial ryegrass (Lolium perenne L.), which will serve as a diploid model for other major grass species.
The achieved results, as specified below, have significantly increased our understanding of the genetic mechanisms underlying grass reproductive traits and how these mechanisms can be used for efficient hybrid breeding in forage and turf grasses.

Self-incompatibility (SI)
The grass family (Poaceae), the fourth largest family of flowering plants, encompasses the most economically important cereal, forage, and energy crops, and exhibits a unique gametophytic self-incompatibility (SI) mechanism that is controlled by at least two multiallelic and independent loci, S and Z. Despite intense research efforts over the last six decades, the genes underlying S and Z remain uncharacterized. We have applied a fine-mapping approach to identify the male component of the S-locus in perennial ryegrass (Lolium perenne L.) and provide multiple evidence that a domain of unknown function 247 (DUF247) gene is involved in its determination. Using a total of 10,177 individuals from seven different mapping populations segregating for S, we narrowed the S-locus to a genomic region containing eight genes, the closest recombinant marker mapping at a distance of 0.016 cM. Of the eight genes cosegregating with the S-locus, a highly polymorphic gene encoding for a protein containing a DUF247 was fully predictive of known S-locus genotypes at the amino acid level in the seven mapping populations. Strikingly, this gene showed a frameshift mutation in self-compatible darnel (Lolium temulentum L.), whereas all of the self-incompatible species of the Festuca-Lolium complex were predicted to encode functional proteins. Our results represent a major step forward toward understanding the gametophytic SI system in one of the most important plant families and will enable the identification of additional components interacting with the S-locus.

Fertility restoring self-compatibility loci (SC)
With the aim to characterize and utilize SC as an important tool for more efficient forage grass breeding, we have established different SC sources from perennial ryegrass and created segregating populations to genetically and functionally characterize these SC sources. From a first population, the genetic location has been determined. Additional plant material and genomics resources will be developed to target the causative genes for SC and to deliver molecular markers for targeted breeding. This will facilitate the introgression of this trait into advanced breeding germplasm, and allow the development of inbred lines for powerful grass hybrids.

Doubled haploid (DH) induction
Attempts to implement hybrid breeding in forage grasses, such as perennial ryegrass (Lolium perenne L.), are hampered by its highly effective SI system, which prevents efficient inbred line production by repeated selfing. Therefore, we have developed an efficient method to obtain homozygous lines in perennial ryegrass using doubled haploid (DH) induction. By means of anther culture, completely homozygous lines can be obtained within one generation cycle. Genotypes with high responsiveness to anther culture have been reported and it has been shown that the trait can be crossed into breeding material. We further aim at developing a molecular marker system to select for high responsiveness and to facilitate the introgression of this trait into advanced breeding germplasm.

Cytoplasmic male sterility (CMS) and its restoration
Cytoplasmic male sterility (CMS) is a widely applied mechanism to control pollination for commercial hybrid seed production and although CMS systems have been identified in perennial ryegrass, they are yet to be fully characterised. We have established a bioinformatics pipeline for efficient identification of candidate restorer of fertility (Rf) genes for CMS. From a high-quality genomic draft of the perennial ryegrass genome, 373 pentatricopeptide repeat (PPR) genes were identified and classified, further identifying 25 restorer of fertility-like PPR (RFL) genes through a combination of DNA sequence clustering and comparison to known Rf genes. This extensive gene family was targeted as the majority of Rf genes in higher plants are RFL genes. These RFL genes were further investigated by phylogenetic analyses, identifying three groups of perennial ryegrass RFLs. These three groups likely represent genomic regions of active RFL generation and identify the probable location of perennial ryegrass PPR-Rf genes.
This pipeline allows for the identification of candidate PPR-Rf genes from genomic sequence data and can be used in any plant species. Functional markers for PPR-Rf genes will facilitate map-based cloning of Rf genes and enable the use of CMS as an efficient tool to control pollination for hybrid crop production.


Ruth Kuehne, (Administration)
Tél.: +41446323835


Life Sciences
Numéro d'enregistrement: 183646 / Dernière mise à jour le: 2016-06-16
Source d'information: SESAM