Unlocking the genetic diversity in Tunisian carrot (Daucus carota subsp. sativus) using phenotypic and molecular markers

Understanding the genetic diversity of a gene pool is fundamental for genebank managers and plant breeders. Within the Mediterranean region, Tunisia is one of the main centers of diversity of several crops including carrot (Daucus carota subsp. sativus). This study evaluated the genetic diversity and population structure of 33 carrot accessions collected from the main cultivation regions in Tunisia and conserved at the National Gene Bank of Tunisia. Phenotypic characterization was performed on 33 accessions by using 34 agro-morphological characters (15 quantitative and 19 qualitative) related to leaves and roots. A considerable phenotypic diversity among accessions was observed for many characters including those related to agronomical performance. Cluster analysis permitted the subdivision of the carrot collection into two distinct groups, independent of their geographic distribution. Fourteen accessions out of the whole collection but representative of genetic diversity in the collection were selected for molecular characterization by using 11 microsatellite markers. Seven SSRs were found to be polymorphic and reproducible. A total of 21 alleles and 30 genotypes were generated with an average polymorphism information content (PIC) of 0.48; suggesting the effectiveness of these markers in the elucidation of the genetic variability of the studied accessions. The grouping of accessions obtained by the UPGMA method using molecular data differs from that obtained by morphological data, but remains independent of the geographical distribution of accessions. No significant correlation was observed between morphological and molecular markers. Despite these differences, both markers provided important information about the diversity of the carrot germplasm, allowing the correct use of these accessions in future breeding programs. Together they provide a powerful tool for future agricultural and conservation tasks.