Dissecting the genetic diversity of cultivated tomato (Solanum lycopersicum) germplasm resources: a comparison of ddRADseq genotyping and microsatellite analysis via capillary electrophoresis and high-resolution melting.

Understanding the genetic diversity of crops is of fundamental importance for the efficient use and improvement of germplasm resources. Different molecular genotyping systems have been implemented for population structure and phylogenetic relationships analyses, among which, microsatellites (SSRs) and single nucleotide polymorphisms (SNPs) markers have been the most widely used. This study reports the efficacy of SNPs detected via double-digest restriction-site-associated DNA sequencing (ddRADseq) and SSRs analyzed via capillary electrophoresis (CE) and high-resolution melting (HRM) in tomato. In total, 21,020 high-quality SNPs, 20 CE-SSRs, and 17 HRM-SSR markers were assayed in a panel of 72 accessions that included a diversified set of landraces, long-shelf-life cultivars and heirlooms with different origins and fruit typology. The results showed how the population structure analysis was consistent using the three genotyping methods, although SNPs were more efficient in distinguishing cultivar types and in measuring the degree of accessions' similarity. Compared to CE-SSR, the analysis of microsatellites via HRM yielded a slightly higher number of alleles (98 vs. 96). HRM-SSR demonstrated a distinction between European and non-European germplasm, better resolving the collection's diversity and being more consistent with SNP data. Phylogenetic trees drawn with independent marker data, detected specific groups of accessions showing robust clusters, highlighting how heirlooms were less heterogeneous than landraces. In addition, the fixation index (F _ST ) revealed a high genetic differentiation between heirlooms and long-shelf-life cultivars, with SNP and SSR-HRM data emphasizing the distinction between cherry and plum types and CE-SSR data between cherry and oxheart types. In all instances, a greater molecular variance was found within the different considered biological statuses, provenances, and typologies rather than among them. This work presents the first attempt to compare the three tomato genotyping techniques in tomato. Findings highlighted how the markers used are complementary for genetic diversity analysis, with SNPs providing better insight and HRM-SSR as a viable alternative to capillary electrophoresis to dissect the genetic structure.

Supplementary information: The online version contains supplementary material available at 10.1007/s13205-024-04141-0.