ND-FISH with New Oligo Probes for Chromosome Identification of Cichorium intybus Revealing Karyotypic Variation and Divergence of Asteraceae Species

Abstract

Chicory (Cichorium intybus L., 2n = 18), belonging to the Asteraceae family, exhibits significant edible, medicinal, and pasture values. Moderate research has been performed on identifying Chicory species’ chromosomes using fluorescence in situ hybridization (FISH) and C-banding. Detailed karyotype comparisons with chromosome nomenclature have not yet been performed for Chicory and similar species. In this study, the tandem repeats (TRs) were predicted and mapped to chromosomal regions based on released C. intybus L. ASM2352571 genome assembly v1, and then compared to the genome of Lettuce (Lactuca sativa L.). Nine new oligo probes were then developed and employed for karyotypic investigation of endive, Lettuce, and Chicory mitotic metaphase using non-denaturing FISH (ND-FISH). By combining the conserved oligo probes for 5S rDNA and 18S rDNA with the unique ND-FISH signals of new TR-oligo probes, we can develop a high-resolution standard karyotype for the cultivars of Lettuce and Chicory. The occurrence of chromosome structure variations from the natural population of Chicory and Lettuce was also revealed by ND-FISH with multiple oligo probes. The current observation of the karyotype differences and divergences of Lactuca and Cichorium and the genomic research offers crucial information about the Asteraceae family’s genetic diversity, chromosomal dynamics, and evolutionary routes.