Comparative Mapping and TargetedCapture TargetedCapture TargetedCapture Sequencing of the Gametocidal Loci in Aegilops sharonensis

Gametocidal (Gc) chromosomes or elements in species such as Aegilops sharonensis Eig are preferentially transmitted to the next generation through both the male and female gametes when introduced into wheat (Triticum aestivum L.). Furthermore, any genes, such as genes that control agronomically important traits, showing complete linkage with Gc elements, are also transmitted preferentially to the next generation without the need for selection. The mechanism for the preferential transmission of the Gc elements appears to occur by the induction of extensive chromosome damage in any gametes that lack the Gc chromosome in question. Previous studies on the mechanism of the Gc action in Ae. sharonensis indicates that at least two linked elements are involved. The first, the breaker element, induces chromosome breakage in gametes, which have lost the Gc elements while the second, the inhibitor element, prevents the chromosome breakage action of the breaker element in gametes which carry the Gc elements. In this study, we have used comparative genomic studies to map 54 single nucleotide polymorphism (SNP) markers in an Ae. sharonensis 4SshL introgression segment in wheat and have also identified 18 candidate genes in Ae. sharonensis for the breaker element through targeted sequencing of this 4SshL introgression segment. This valuable genomic resource will aide in further mapping the Gc locus that could be exploited in wheat breeding to produce new, superior varieties of wheat. Certain Aegilops species have an evolutionary unique mechanism that ensures the transmission of specific regions of their genomes to the next generation when introduced to wheat. This phenomenon was first recognized when specific chromosomes, Gc chromosomes (Endo, 1979a) or “Cuckoo” chromosomes (Finch et al., 1984), were observed to be preferentially transmitted through both the male and female gametes in a wheat background. Gc chromosomes or elements have been identified in several S genome species on different chromosomes (Endo, 1982, 1985; Maan, 1975; Miller et al., 1982; Tsujimoto, 1994; Tsujimoto and Tsunewaki, 1984) as well as in the C genome (Endo, 1979b, 1988; Endo and Tsunewaki, 1975; Endo and Katayama, 1978). A Gc element has also been reported on chromosome 7el2 of Thinopyrum ponticum (Podp.) Barkworth & D. R. Dewey (formerly Agropyron elongatum; Kibirige-Sebunya and Knott, 1983) and on chromosome 4Mg of A. geniculata (Kynast et al., 2000). While the Gc action in each of these species results in the preferential transmission of each of these chromosomes, Published in Plant Genome Volume 10. doi: 10.3835/plantgenome2016.09. 0090 © Crop Science Society of America 5585 Guilford Rd., Madison, WI 53711 USA This is an open access article distributed under the CC BY license (https://creativecommons.org/licenses/by/4.0/). S. Grewal, B. Ndreca, I. P. King, and J. King, Division of Plant and Crop Sciences, School of Biosciences, The University of Nottingham, Sutton Bonington Campus, Loughborough, LE12 5RD, UK; L-J. Gardiner, Institute of Integrative Biology, University of Liverpool, Crown Street, Liverpool, L69 7ZB, UK; E. Knight and G. Moore, Crop Genetics Department, John Innes Centre, Norwich Research Park, Colney, Norwich NR4 7UH, UK. Received 6 Sept. 2016. Accepted 27 Jan. 2017. *Corresponding author (surbhi.grewal@ nottingham.ac.uk). Assigned to Associate Editor Peter Langridge. Abbreviations: BAM, binary alignment map; DAPI, 4’,6-diamidino2-phenylindole; EMS, ethyl methanesulfonate; EST, expressed sequence tag; FISH, fluorescence in situ hybridization; FITC, Alexa Fluor 488; Gc, gametocidal; GATK, Genome Analyis ToolKit; GISH, genomic in situ hybridization; IL, introgression line; InDel, insertion/deletion; KASP, Kompetitive Allele Specific PCR; NGS, next-generation sequencing; PCR, polymerase chain reaction; PM, pseudomolecule; SNP, single nucleotide polymorphism; SSC, salinesodium citrate; TRITC, Alexa Fluor 594. Published online July 13, 2017