Combining genome size and pollen morphology data to study species relationships in the genus Daucus (Apiaceae)

Abstract

Background The genus Daucus (Apiaceae) comprises about 40 wild species and the cultivated carrot, a crop of great economic and nutritional importance. The rich genetic diversity of wild Daucus species makes them a valuable gene pool for carrot improvement breeding programs. Therefore, it is essential to have good knowledge of the genome structure and relationships among wild Daucus species. To broaden such knowledge, in this research, the nuclear DNA content for 14 Daucus accessions and four closely related species was estimated by flow cytometry and their pollen morphology was analyzed by light and scanning electron microscopy (SEM). Results The flow cytometric analysis showed a 3.2-fold variation in the mean 2C values among Daucus taxa, ranging from 0.999 (D. carota subsp. sativus) to 3.228 pg (D. littoralis). Among the outgroup species, the mean 2C values were 1.775–2.882 pg. The pollen grains of Daucus were tricolporate, mainly prolate or perprolate (rarely) in shape, and mainly medium or small (rarely) in size (21.19–40.38 µm), whereas the outgroup species had tricolporate, perprolate-shaped, and medium-sized (26.01–49.86 µm) pollen grains. In the studied taxa, SEM analysis revealed that exine ornamentation was striate, rugulate, perforate, or the ornamentation pattern was mixed. At the time of shedding, all pollen grains were three-celled, as evidenced by DAPI staining. We also found high positive correlations between the length of the polar axis (P) and the length of the equatorial diameter (E) of pollen grains, as well as between P and P/E. However, when comparing cytogenetic information with palynological data, no significant correlations were observed. Conclusions This study complements the information on the nuclear DNA content in Daucus and provides comprehensive knowledge of the pollen morphology of its taxa. These findings may be important in elucidating the taxonomic relationships among Daucus species and can help in the correct identification of gene bank accessions. In a broader view, they could also be meaningful for the interpretation of evolutionary trends in the genus.

Scanning electron microscopic exploration of intricate pollen morphology and antimicrobial potentials of gourd family

“…Scanning electron microscopy (SEM) has made a significant impact on biology and its various academic fields in this era (Kadluczka et al, 2022). Anatomical, palynological, and morphological trends among angiosperms, as well as the consistent features used to classify plant species, are explained by SEM (Citak et al, 2022).…”

Palynological features and taxonomic significance for 16 species of Gagea (Liliaceae) from Xinjiang, China

“…Pollen morphology is scarcely affected by ecological conditions; thus, it is more stable than external macrographical morphology and has high genetic stability (Zarre and Zarrei 2005;Blackmore 2007;Kadluczka et al 2022). Pollen size and morphology, such as shape, aperture type, mesocolpium diameter, exine ornamentation and perforation size, have great significance in plant taxonomy and pollen characteristics can be used to infer genetic relationships between ecological groups (Li et al 2020) or interspecific taxonomic ranks (Heidarian et al 2021).…”

Comparative Fruit Morphology and Anatomy of Wild Relatives of Carrot (Daucus, Apiaceae)

“…Most Daucus species are diploids with chromosome numbers of 2n = 16, 18, 20, or 22; however, some tetra-and hexaploids 2 of 17 have also been reported [15,17,18]. Regarding the genome size within the genus, nuclear DNA content estimates based on flow cytometry are available for several wild species and subspecies, as well as for many cultivated carrots, ranging from 0.920 to 3.228 pg/2C DNA [19][20][21].…”

“…Given the significance of wild Daucus species and the great economic importance of the cultivated carrot, as well as the taxonomical usefulness of fruit structural characteristics in Apiaceae, this study aimed to compare the fruit morphology and anatomy of Daucus taxa using light and scanning electron microscopy (SEM) and to evaluate the diagnostic value of these characteristics. In this study, which is a continuation of our previous work [21], we selected a representative sample that covered the two main Daucus subclades (13 taxa) and four closely related non-Daucus species. We used the same accessions that have commonly been used in previous phylogenetic and (cyto)taxonomic research on the genus [9,12,13,21,39].…”

“…In this study, which is a continuation of our previous work [21], we selected a representative sample that covered the two main Daucus subclades (13 taxa) and four closely related non-Daucus species. We used the same accessions that have commonly been used in previous phylogenetic and (cyto)taxonomic research on the genus [9,12,13,21,39].…”