Construction of a consensus genetic map of Eragrostis curvula

Abstract

Eragrostis curvula is a forage grass used by our group as a model for the study of displosporous apomixis. It includes genotypes with different ploidy levels (from 2X to 8X, with X = 10) and reproductive modes (sexual and facultative or obligate apomixis). Previously, our group built the first highly saturated genetic linkage map of E. curvula using a mapping population generated from the cross between two tetraploid genotypes, OTA-S and Don Walter. At that time, the small size of the mapping population (61 individuals) did not allow the generation of a consensus map between the maternal and paternal maps. However, a map was constructed for each parental genotype and the apomeiosis-linked locus (APO-locus) was located in the paternal map. The objective of this work was to expand the mapping population using the same parental lines in order to build a high-density consensus genetic map where to position the APO-locus and to make syntenic analysis. The new mapping population consisted of 109 hybrid individuals coming from the previous population and new ones coming from the new crosses. This population was phenotyped by cytoembryology and through the use of a dominant molecular marker linked to apomeiosis, resulting in 48 sexual offprings and 61 apomictic ones. The genotyping was performed with SNPs using the DArT-Seq technology (SAGA-CIMMYT, Mexico). For the map construction single dose allele markers and biparental SNPs markers were used. Linkage maps for each parent and a consensus map were built. The consensus genetic map contains a total of 1,132 markers, of which 587 were paternal, 514 maternal and 31 biparental. The total length of the linkage map was 4,605 cM and it was made up of 20 linkage group (LG). Synteny analysis was performed using the genome assembly of E. curvula (cv. Victoria). In the paternal map, a region delimited by three markers was found that cosegregates with apomeiosis (APO-locus). The APO-locus delimited a region of 11,322,729 bp in the reference genome of cv. Victoria. The construction of this mapping population, added to the of E. curvula consensus map are valuable elements for future studies of apomixis.