Prunus L. subgen. Cerasus Mill. (Rosaceae) contains numerous economically important species, including fruit trees and ornamental plants. This study compares the leaf anatomy and calcium oxalate crystal types of 98 individuals of 14 Prunus subgen. Cerasus taxa from Turkey. We stained leaf sections with Safranin‐Alcian Blue double stain and mapped calcium oxalate crystals under light microscope with polarized light. We used one‐way ANOVA to determine the statistical significance of quantitative data. Significant quantitative and qualitative data were analyzed using PCoA to establish relationships among taxa. We observed three different crystal distribution patterns and three crystal types, finding druses present in all taxa, while some taxa also have sand or prismatic forms. Most characters showed high variation. Our analysis shows that vascular bundle, midrib, upper epidermis and lower epidermis width/length ratios; midrib epidermis, upper epidermis and phloem cell lengths; upper epidermis and lower epidermis cell widths and lower cuticle thickness are not taxonomically useful, while features of the bundle sheath, epidermis cell surface, phloem fibers, mesophyll layers and angle of blade between the midrib can be used in conjunction with other characters to distinguish certain taxa. Overall, PCoA delineated two rough groups, separating P. avium, P. cerasus and P. mahaleb from the rest of the studied taxa. In investigating the anatomical variation between different individuals of these taxa, we found that some features previously used in infraspecific taxa, such as trichomes, varied sometimes even within an individual, casting doubt on the wisdom of using these for systematic work in subgenus Cerasus.
Crocus istanbulensis (B.Mathew) Rukšāns is one of the most endangered Crocus species in the world and has an extremely limited distribution range in Istanbul. Our recent field work indicates that no more than one hundred individuals remain in the wild. In the present study, we used genome skimming to determine the complete chloroplast (cp) genome sequences of six C. istanbulensis individuals collected from the locus classicus. The cp genome of C. istanbulensis has 151,199 base pairs (bp), with a large single-copy (LSC) (81,197 bp), small single copy (SSC) (17,524 bp) and two inverted repeat (IR) regions of 26,236 bp each. The cp genome contains 132 genes, of which 86 are protein-coding (PCGs), 8 are rRNA and 38 are tRNA genes. Most of the repeats are found in intergenic spacers of Crocus species. Mononucleotide repeats were most abundant, accounting for over 80% of total repeats. The cp genome contained four palindrome repeats and one forward repeat. Comparative analyses among other Iridaceae species identified one inversion in the terminal positions of LSC region and three different gene (psbA, rps3 and rpl22) arrangements in C. istanbulensis that were not reported previously. To measure selective pressure in the exons of chloroplast coding sequences, we performed a sequence analysis of plastome-encoded genes. A total of seven genes (accD, rpoC2, psbK, rps12, ccsA, clpP and ycf2) were detected under positive selection in the cp genome. Alignment-free sequence comparison showed an extremely low sequence diversity across naturally occurring C. istanbulensis specimens. All six sequenced individuals shared the same cp haplotype. In summary, this study will aid further research on the molecular evolution and development of ex situ conservation strategies of C. istanbulensis.
In this study, we explore the relationships among taxa of Prunus subgenus Cerasus in Turkey using a combination of macromorphology, micromorphology and molecular techniques. We recorded qualitative and quantitative characteristics of flowers, leaves, seeds and endocarp for 96 populations representing 14 taxa of Prunus subgenus Cerasus. ITS, matK, ycf1, trnL-trnF DNA sequence data were used to reconstruct phylogenetic trees for this group. Haplotype analyses results found 11 haplotypes among the samples used in this study. We also note that the infraspecific taxa of Cerasus angustifolia (=P. albicaulis), P. mahaleb, P. microcarpa and P. prostrata, as described by previous authors, do not exhibit significant differences even among the features of foliar morphology that are so often used to distinguish them from one another. As a general rule, our analyses indicate that the highly variable features of leaf micromorphology and endocarp and seed micromorphology are not taxonomically significant. In contrast, although floral morphology is often overlooked in systematic studies of Prunus subgenus Cerasus, we found several taxonomically useful flower characters, including sepal indumentum, hypanthium shape and indumentum and petal shape. This work clarifies the infraspecific relationships of members of Prunus subgenus Cerasus in Turkey and solves some taxonomic problems.
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