With the increasing availability of EST databases and whole genome sequences, SNPs have become the most abundant and powerful polymorphic markers. However, SNP chip data generally suffers from ascertainment biases caused by the SNP discovery and selection process in which a small number of individuals are used as discovery panels. The ongoing International Citrus Genome Consortium sequencing project of the highly heterozygous Clementine and sweet orange genomes will soon result in the release of several hundred thousand SNPs. The primary goals of this study were: (i) to estimate the transferability within the genus Citrus of SNPs discovered from Clementine BACend sequencing (BES), (ii) to estimate bias associated with the very narrow discovery panel, and (iii) to evaluate the usefulness of the Clementine-derived SNP markers for diversity analysis and comparative mapping studies between the different cultivated Citrus species.

• Premise of the study: Single nucleotide polymorphism (SNP) markers based on Competitive Allele‐Specific PCR (KASPar) were developed from sequences of three Citrus species. Their transferability was tested in 63 Citrus genotypes and 19 relative genera of the subfamily Aurantioideae to estimate the potential of SNP markers, selected from a limited intrageneric discovery panel, for ongoing broader diversity analysis at the intra‐ and intergeneric levels and systematic germplasm bank characterization.• Methods and Results: Forty‐two SNP markers were developed using KASPar technology. Forty‐one were successfully genotyped in all of the Citrus germplasm, where intra‐ and interspecific polymorphisms were observed. The transferability and diversity decreased with increasing taxonomic distance.• Conclusions: SNP markers based on the KASPar method developed from sequence data of a limited intrageneric discovery panel provide a valuable molecular resource for genetic diversity analysis of germplasm within a genus and should be useful for germplasm fingerprinting at a much broader diversity level.

Tetraploid non-apomictic citrus genotypes are key female parents for 4x × 2x hybridizations aimed at producing seedless triploid hybrids. However, the extent to which different tetraploidization methods affect genome integrity remains insufficiently characterized at a genome-wide scale. In this study, genotyping-by-sequencing (GBS) was used to evaluate marker-based genomic stability in ten tetraploid plants of ‘Clemenules’, ‘Fina’, and ‘Marisol’ clementines obtained via colchicine treatment, in vitro adventitious organogenesis, or somatic cybridization. Diploid parental plants, two haploid plants of ‘Clemenules’ and ‘Fina’ clementines, and one doubled haploid plant of ‘Clemenules’ clementine were included, being the haploid and double haploid essential to resolve allelic phases. After quality filtering, 3333 SNP (Single Nucleotide Polymorphism) markers distributed across the nine citrus chromosomes were identified and used to compare allele dosage patterns along the genome. Across all GBS-covered regions, no major marker-based genomic gains or losses were detected in any tetraploid plant. These results indicate that, at the resolution provided by GBS, all three tetraploidization methods largely preserve chromosome structure, supporting their suitability for citrus triploid breeding programs based on 4x × 2x sexual hybridizations.

Polyploidization plays a major role in citrus breeding, particularly in generating triploid hybrids through controlled crosses between diploid female and t