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A new genetic locus for self-compatibility in the outcrossing grass species perennial ryegrass (Lolium perenne).

  • Slatter, Lucy M1, 2
  • Barth, Susanne3
  • Manzanares, Chloe4
  • Velmurugan, Janaki3, 5
  • Place, Iain1
  • Thorogood, Daniel1
  • 1 Institute of Biological, Environmental and Rural Sciences, Gogerddan, Aberystwyth University, Aberystwyth, UK.
  • 2 KWS UK Ltd, Thriplow, Royston, Hertfordshire, UK.
  • 3 Teagasc, Crops Environment and Land Use Programme, Oak Park Research Centre, Carlow, Ireland. , (Ireland)
  • 4 ETH Zurich, Department of Environmental Systems Science, Universitätstrasse 2, 8092 Zürich, Switzerland. , (Switzerland)
  • 5 APC Microbiome Institute, Biosciences Building, University College Cork, Ireland. , (Ireland)
Published Article
Annals of Botany
Oxford University Press
Publication Date
May 07, 2021
DOI: 10.1093/aob/mcaa140
PMID: 32856713


Self-incompatibility (SI) is a physiological mechanism that many flowering plants employ to prevent self-fertilization and maintain heterozygosity. In the grass family this is known to be controlled by a two locus (S-Z) system; however, the SI system is intrinsically leaky. Modifier genes of both the S and Z loci and a further locus, T, are known to override SI leading to self-fertilization and self-seed production. This has implications for the ecological and evolutionary success as well as the commercial breeding of grasses. Here we report a study where the genetic control of self-compatibility (SC) was determined from the results of self-pollinating an F2 population of perennial ryegrass from two independently derived inbred lines produced by single-seed descent. In vitro self-pollinations of 73 fertile plants were analysed. A genetic association analysis was made with a panel of 1863 single-nucleotide polymorphism (SNP) markers, generated through genotype-by-sequencing methodology. Markers were placed on a recombination map of seven linkage groups (LGs) created using Joinmap v.5. The seed set on self- and open-pollinated inflorescences was determined on 143 plants, including the 73 plants analysed for self-pollination response. Self-pollinations revealed a bimodal distribution of percentage SC with peaks at 50 and 100 %. A single quantitative trait locus (QTL) was identified with peak association for marker 6S14665z17875_11873 that mapped to LG 6. Peak position was associated with maximum marker segregation distortion. The self-compatible plants were equally fecund after self- and open pollination. This is the first report in the Poaceae family of an SC locus located on LG 6. This new SC QTL discovery, as well as indicating the complex nature of the pollen-stigma recognition process and its evolutionary significance, provides an additional source of SC for breeding perennial ryegrass. © The Author(s) 2020. Published by Oxford University Press on behalf of the Annals of Botany Company.

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