Fine mapping a self-fertility locus in perennial ryegrass
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A self-fertility locus was fine mapped to a 1.6 cM region on linkage group 5 in a perennial ryegrass population. This locus was the main determinant of pollen self-compatibility.
In grasses, self-incompatibility (SI) is characterized by a two-loci gametophytic (S and Z) mechanism acting together in the recognition and inhibition of self-pollen. Mutations affecting the expression of SI have been reported in a few grass species. In perennial ryegrass (Lolium perenne L.), a mutation independent from S and Z, and mapping on linkage group 5 (LG 5), was previously reported to produce self-fertile plants. Here, we describe fine mapping of the self-fertility (SF) gene in a perennial ryegrass population and determine whether there is any effect of other genomic regions on the pollen compatibility. The phenotypic segregation of SF showed a bimodal distribution with one mean at 49% pollen compatibility and the other at 91%. Marker-trait association analysis showed that only markers on LG 5 were significantly associated with the trait. A single gene model explained 82% of the observed variability and no effects of the other regions were detected. Using segregation and linkage analysis, the SF locus was located to a 1.6 cM region on LG 5. The flanking marker sequences were aligned to rice and Brachypodium distachyon reference genomes to estimate the physical distance. We provide markers tightly linked to SF that can be used for introgression of this trait into advanced breeding germplasm. Moreover, our results represent a further step towards the identification of the SF gene in LG 5.
The authors would like to thank USDA’s National Institute of Food and Agriculture (Project numbers: IOW04314, IOW01018), Swiss National Science Foundation (SNSF Professorship Grant no. PP00P2 138988), and Hatch Multistate Project NC-007, as well as the Plant Sciences Institute, RF Baker Center for Plant Breeding and K.J. Frey Chair in Agronomy at Iowa State University for funding or supporting this work and also, the Agencia Nacional de Investigación e Innovación (ANII) of Uruguay for contributing with funds to JD’s doctorate (Ref.: POS_EXT_2014_1_105636).
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Conflict of interest
The authors declare that they have no conflict of interest.
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