Search Results (27)

A review of the known diploid species in Hieracium L. s.s. (Asteraceae, Cichorieae) is presented. This article aims to summarize the current knowledge of the taxa with the basic ploidy level in the genus (2n = 2x = 18), as these entities are supposed to have originated the outstanding diversity observed nowadays, which is largely ascribable to polyploid microspecies. The study of extant diploid species is crucial for the understanding of the speciation dynamics that occurred in hawkweeds. All available cytological data in the literature, pertinent to Europe and adjacent countries, are included to have an overview of the obligately sexual species in this genus and highlight gaps and uncertainties. In order to preliminarily investigate the geographical distribution, all records are georeferenced and projected on a map to highlight the hotspots of Hieracium diversity. A brief account of each taxon is included, with some additional considerations and remarks on doubtful records. Full article

The allopolyploid complexes in Crocus series Verni represent taxonomic challenges due to their variable or mostly overlapping morphology with one parental species. Moreover, their diploid ancestors remain unidentified, even with genome-wide SNP data. One such case, collected from the southeasternmost point of the series’ geographical distribution, is herein characterised and described as a new species, C. bachofenii. This study integrates phylogenomics and cytogenetics to infer the parental origin of C. bachofenii and establish its diagnostic morphological characteristics. Genome skimming of C. bachofenii and 10 other C. ser. Verni species enabled the development of novel satellite repeats as cytogenetic markers and the assembly of their complete chloroplast genomes that were employed for phylogenetic analysis alongside GBS data. The allopolyploid origin of C. bachofenii (2n = 16) was confirmed with C. vernus as the maternal parent. The probably extinct paternal parent was affiliated with a clade comprising C. heuffelianus, C. tommasinianus, C. kosaninii, and C. bertiscensis. Morphologically, C. bachofenii is distinguished by larger flowers, perigone segment coloration, and a stigma–anther ratio from its close relatives. In conclusion, its phylogenetic affiliation, distinctive cytological status, and unique morphological features justified the description of this taxon as a new species. Full article

Polyploid plants often exhibit superior yield, stress resistance, and quality. In this study, homologous tetraploid wucai (Brassica campestris L.) was successfully obtained by spraying seedling growth points with colchicine. The morphological, cytological, and physiological characteristics of diploid and tetraploid wucai were analyzed, and transcriptomic sequencing was performed at three stages of development. Tetraploid seedings grew slowly but exhibited darker leaves, enlarged organs and cells, increased stomatal volume, decreased stomatal density, improved nutritional content, and enhanced photosynthesis. Differentially expressed genes (DEGs) identified in diploid and tetraploid plants at three stages of development were enriched in different pathways. Notably, DEGs identified in the tetraploid plants were specifically enriched in starch and sucrose metabolism, pentose and glucuronate interconversions, and ascorbate and aldarate metabolism. In addition, we found that the light green module was most relevant to ploidy, and DEGs in this module were significantly enriched in the glycolysis/gluconeogenesis and TCA cycle pathways. The differential expression of key glycolysis-associated genes at different developmental stages may be the driver of the observed differences between diploid and tetraploid wucai. This study lays a technical foundation for the development of polyploid wucai germplasm resources as well as the breeding of new varieties with improved quality, yield, and stress resistance. It also provides a good empirical reference for the genetic breeding of closely related Brassica species. Full article

Polyploidization produces abundant phenotypic variation. Little is currently known about adventitious root (AR) development variation due to polyploidization. In this study, we analyzed the morphological, cytological, and physiological variations in AR development between tetraploid and diploid Populus plants during in vitro rooting culture. Compared to the diploids, the AR formation times and rooting rates of the tetraploids’ stem explants had non-significant changes. However, the tetraploid ARs exhibited significantly slower elongation growth than the diploid ARs. Cytological observation showed that the tetraploid ARs were characterized by shorter root meristems and reduced meristem cell numbers, suggesting the reasons for the slow AR elongation. Analysis of hormones and related metabolites during AR development demonstrated that the total auxin, cytokinin, and jasmonic acid contents were significantly lower in the tetraploid ARs than in those of the diploids, and that the ratio of total auxins to total CKs at 0 h of AR development was also lower in the tetraploids than in the diploids, whereas the total salicylic acid content of the tetraploids was consistently higher than that of the diploids. qPCR analysis showed that the expression levels of several hormone signaling and cell division-related genes in the tetraploid ARs significantly differed from those in the diploids. In conclusion, the slow elongation of the tetraploid ARs may be caused by the endogenous hormone-mediated meristem shortening. Our findings enhance the understanding of polyploidization-induced variation in AR development of forest trees. Full article

Groups with morphological stasis are an interesting framework to address putative cryptic species that may be hidden behind traditional taxonomic treatments, particularly when distribution ranges suggest disjunct and environmentally heterogeneous biogeographic patterns. New hypotheses of delimitation of evolutionary independent units can lead to the identification of different biogeographic processes, laying the foundation to investigate their historical and ecological significance. Jasione is a plant genus with a distribution centered in the Mediterranean basin, characterized by significant morphological stasis. Within the western Mediterranean J. gr. crispa species complex, J. sessiliflora s.l. and allied taxa form a distinct group, occupying environmentally diverse regions. At least two ploidy levels, diploid and tetraploid, are known to occur in the group. The internal variability is assessed with phylogenetic tools, viz. GMYC and ASAP, for species delimitation. The results are compared with other lines of evidence, including morphology and cytology. The fitting of distribution patterns of the inferred entities to chorological subprovinces is also used as a biogeographical and environmental framework to test the species hypothesis. Despite the scarcity of diagnostic morphological characters in the group, phylogenetic delimitation supports the description of at least one cryptic species, a narrow endemic in the NE Iberian Peninsula. Moreover, the results support the segregation of a thermophilic group of populations in eastern Iberia from J. sessiliflora. Ploidy variation from a wide geographical survey supports the systematic rearrangement suggested by species delimitation. Taxonomic reorganization in J. sessiliflora s.l. would allow ecological interpretations of distribution patterns in great accordance with biogeographical regionalization at the subprovince level, supporting geobotanical boundaries as a framework to interpret species ecological coherence of cryptic lineages. These results suggest that species differentiation, together with geographic isolation and polyploidization, is associated with adaptation to different environments, shifting from more to less thermophilic conditions. Thus, the recognition of concealed evolutionary entities is essential to correctly interpret biogeographical patterns in regions with a complex geologic and evolutionary history, such as the Mediterranean basin, and biogeographical units emerge as biologically sound frameworks to test the species hypothesis. Full article

The plecos (Loricariidae) fish represent a great model for cytogenetic investigations due to their variety of karyotypes, including diploid and polyploid genomes, and different types of sex chromosomes. In this study we investigate Transancistrus santarosensis a rare loricariid endemic to Ecuador, integrating cytogenetic methods with specimens’ molecular identification by mtDNA, to describe the the species karyotype. We aim to verify whether sex chromosomes are cytologically identifiable and if they are associated with the accumulation of repetitive sequences present in other species of the family. The analysis of the karyotype (2n = 54 chromosomes) excludes recent centric fusion and pericentromeric inversion and suggests the presence of a ZZ/ZW sex chromosome system at an early stage of differentiation: the W chromosome is degenerated but is not characterized by the presence of differential sex-specific repetitive DNAs. Data indicate that although T. santarosensis has retained the ancestral diploid number of Loricariidae, it accumulated heterochromatin and shows non-syntenic ribosomal genes localization, chromosomal traits considered apomorphic in the family. Full article

Understanding the cytological pattern of genome size and ploidy level of the bermudagrass (Cynodon dactylon) is vital to explore the evolution pattern and breeding of the species. To study the diversification of the cytological pattern of bermudagrass along the longitudinal gradient, the genome size and ploidy level were measured and explored with the relationship to climate factors. The corresponding ploidy level was verified through the mitotic chromosome counts method. Bermudagrass accessions ploidy level included diploids, triploid, tetraploid, pentaploid and hexaploid with a basic chromosome number of x = 9. The major ploidy level was tetraploid (45%) and aneuploidy was commonly discovered in collected regions. Mean genome size of bermudagrasswas was estimated to be 1.31 pg/1Cx along longitudinal gradient. The 1Cx values of diploid were higher than that of triploid and tetraploid, while the tetraploid had minimum basic genome size. In the current study, we observed that genome downsizing exists in tetraploids of Cynodon dactylon. Tetraploids have a wider distribution than other ploidy levels, especially in arid areas, occupying a relatively high proportion. In addition, at the same ploidy level, genome size was remarkably variable in the current study. The coefficient of determination analysis showed that longitude and mean annual rainfall were significantly correlated to genome size rather than ploidy level. This cytological study will be helpful for further genetic mechanisms and molecular characteristics to landscape adaptation of bermudagrass. Full article

Interspecific hybridization and accompanying backcross between crops and relatives have been recognized as a powerful method to broaden genetic diversity and transfer desirable adaptive traits. Crosses between radish (Raphanus sativus, RR, 2n = 18) and Brassica oleracea (CC, 2n = 18), which formed allotetraploid Raphanobrassica (RRCC, 2n = 36), initiated the construction of resynthetic allopolyploids. However, these progenies from the backcrosses between Raphanobrassica and the two diploid parents have not been well deciphered. Herein, thousands of backcrosses using both Raphanobrassica and the two diploid parents as pollen donors were employed. Several hybrids with expected (2n = 27) and unexpected chromosome numbers (2n = 26 and 2n = 36) were obtained. Fluorescence in situ hybridization (FISH) analysis with R-genome-specific sequences as probes demonstrated that the genome structures of the two expected hybrids were RRC and CCR, and the genome structures of the three unexpected hybrids were RRRC, CCCR, and RRC’ (harbouring an incomplete C genome). The unexpected hybrids with extra R or C genomes showed similar phenotypic characteristics to their expected hybrids. FISH analysis with C-genome-specific sequences as probes demonstrated that the unexpected allotetraploid hybrids exhibited significantly more intergenomic chromosome pairings than the expected hybrids. The expected and unexpected hybrids provide not only novel germplasm resources for the breeding of radish and B. oleracea but also very important genetic material for genome dosage analysis. Full article

Dendrobium officinale Kimura et Migo is an orchid with both medicinal and edible values and a high economic value. The wild resources of D. officinale are in an endangered state. Compared with the wild D. officinale, cultivated D. officinale exhibits inferior quality and a low content of medicinal components. Polyploid induction is a conventional breeding tool for genome doubling of species, which can effectively increase the total amount of plant components to improve the medicinal efficacy of D. officinale. In this study, D. officinale tetraploids were generated by treating the protocorms with colchicine. Morphological observations showed that tetraploids exhibited decreased plant size and leaf shape index and increased stem diameter. Cytological observations showed that the polyploid plants had larger stomata and a lower number of stomata per unit area compared with normal plants. The highest stomata variation of 30.00% was observed when the plant was treated with 0.3% colchicine for 24 h. Chromosomal observations showed that treatment of plants with 0.2% colchicine for 48 h resulted in the highest tetraploid induction rate of 10.00%. A total of 10 tetraploids were successfully obtained by inducing plant protoplasts with colchicine. The number of diploid D. officinale chromosomes was 38 with a base number of 19, and the karyotype formula was 2n = 2x = 38 = 24m + 14sm with a karyotype asymmetry coefficient of 60.59%, belonging to type 2B. The number of tetraploid D. officinale chromosomes was 76 with a base number of 19, and the karyotype formula was 2n = 4x = 76 = 58m + 18sm with a karyotype asymmetry coefficient of 60.04%, belonging to type 2B. This study determined the optimal mutagenesis treatment based on the chromosome observation results, investigated the relationship between the phenotype and ploidy level, and generated the polyploid germplasm of D. officinale, thereby laying the foundation for the breeding of new D. officinale cultivars enriched with compounds of medicinal value. Full article

Artificially induced polyploidization is one of the most effective techniques for improving the biological properties and creating new cultivars of fruit trees. Up to now, systematic research on the autotetraploid of sour jujube (Ziziphus acidojujuba Cheng et Liu) has not been reported. ‘Zhuguang’ is the first released autotetraploid sour jujube induced with colchicine. The objective of this study was to compare the differences in the morphological, cytological characteristics, and fruit quality between diploid and autotetraploid. Compared with the original diploid, ‘Zhuguang’ showed dwarf phenotypes and decreased tree vigor. The sizes of the flowers, pollen, stomata, and leaves of ‘Zhuguang’ were larger. Perceptible darker green leaves were observed in ‘Zhuguang’ trees owing to increased chlorophyll contents, which led to higher photosynthesis efficiency and bigger fruit. The pollen activities and the contents of ascorbic acid, titratable acid, and soluble sugar in the autotetraploid were lower than those in diploids. However, the cyclic adenosine monophosphate content in autotetraploid fruit was significantly higher. The sugar/acid ratio of autotetraploid fruit was higher than that of diploid fruit, which made the autotetraploid fruit taste different and better. The results indicated that the autotetraploid we generated in sour jujube could greatly meet the goals of our multi-objective optimized breeding strategies for improving sour jujube, which includes tree dwarfing, increased photosynthesis efficiency, and better nutrient values and flavors as well as more bioactive compounds. Needless to say, the autotetraploid can also serve as material for generating valuable triploids or other types of polyploids and are also instrumental in studying the evolution of both sour jujube and Chinese jujube (Ziziphus jujuba Mill.). Full article

Sugar beet (Beta vulgaris L.) is cultivated in temperate climates worldwide to produce sugar. The production of sugar beet and other plants is in danger due to the world’s increasingly salinized soils. Although different sugar beet genotypes exist at various ploidy levels, most of them are diploid (2X) with 18 chromosomes. The majority of polyploid plants have different variations, morphologies, and anatomy. Diploid and polyploid plants especially have different morphology, physiology, cellularity, and biochemistry. As a result, polyploidy has been identified as an essential component in determining plant salt tolerance. To evaluate the effects of salt (NaCl) stress on sugar beet genotypes, diploid (2X), triploid (3X), and tetraploid (4X) genotypes were exposed to 0 (control), 50, and 150 mM NaCl concentrations for seven weeks. Under control conditions, the diploid (2X) genotype showed higher growth performance compared to the tetraploid (4X) and triploid (3X) genotypes, respectively. Regarding germination and early-stage growth performance, a reduction of about 50% was observed in the diploid (2X) genotype under salt stress compared to the control condition. The diploid (2X) genotype showed higher germination, a greater salt tolerance index, and better seedling growth performance than the other ploidy levels. Late-stage growth, leaf length, leaf width, leaf area, cytological findings, and total chlorophyll content were all shown to be higher and less reduced (around 30%) under salt stress in diploid (2X) genotypes. Even though all of the findings in this study showed a decrease when plants were exposed to salt (NaCl), the diploid (2X) ploidy level plants displayed more robust growth and development than the triploid (3X) and tetraploid (4X) genotypes. Full article

Ginger (Zingiber officinale Rosc.) is an important spice crop valued for its flavored and medical properties. It is susceptible to soil-borne diseases, which can cause considerable economic loss to growers. In vitro culture is feasible for the propagation of disease-free ginger plants, but has several disadvantages when producing seed rhizomes that can be commercially used, such as long cultivation cycles (usually 2–3 years) and occurrence of somaclonal variation. In this study, dynamic changes in the morphological characteristics of in vitro-propagated disease-free plants of ‘Wuling’ ginger were evaluated by continuous observation and measurement at 30-day intervals, and morphological variants were screened and characterized by agronomic, cytological, and molecular analysis at harvest. Results showed that the plants grew rapidly within 120 days after planting, and the most active growth period was from 60 to 120 days. Eight plants with clear and stable morphological differences were screened out from approximately 2000 plants grown in the field, and they could be classified into two groups (VT1 and VT2) based on tiller number, plant height, leaf color, and leaf shape. By flow cytometry analysis and chromosome counting, the VT1 was confirmed to be diploid, with the shortest plant height, the largest number of tillers and rhizome knobs, and the smallest tiller diameter and rhizome size among the three types of plants. The VT2 was mixoploid, consisting of diploid and tetraploid cells, with significantly reduced tiller number and rhizome knobs, significantly larger stomatal guard cells/apertures, and significantly lower stomatal density. SSR analysis detected DNA band profile changes in six out of the eight variants, including one plant of the VT1 and all the VT2 plants. The findings of this study might contribute to the commercial production of disease-free seed rhizomes in ginger, and the characterized somaclonal variants could provide useful germplasm resources for future breeding. Full article

Anthropogenic activities, such as the movement of plants through greening, can result in genetic disturbance that can interfere with local adaptation in wild populations. Although research is underway to prevent genetic disturbance associated with greening, genetic disturbance of intraspecific polyploidy, which is estimated to be present in 24% of vascular plants, has not been well studied. Liriope muscari is a polyploid complex with known diploid (2n = 36), tetraploid (2n = 72), and hexaploid (2n = 108) forms. The plants of this species tolerate dry and hot conditions and are therefore frequently used for greening and gardening. However, the distribution of this polyploid in Japan, its genetic structure, and genetic disturbance are not known. In this study, we investigated the polyploidy distribution and genetic structure in naturally distributed L. muscari in Japan using chloroplast DNA (cpDNA) haplotypes and nuclear DNA (nDNA). Commercially produced individuals were also studied and compared with natural populations to assess any genetic disturbance of the ploidy complex in this species. Chromosome counts, cpDNA, and nDNA results showed three genetically and cytologically distinct groups in Japan: first, a tetraploid group in mainland Japan; second, a hexaploid group in the Ryukyu Islands; and third, a diploid and tetraploid group in the Ryukyu Islands. Significant isolation by distance was also detected within the three groups (p = 0.001). Genetic disturbance due to greening and gardening should be avoided among the three groups. Genetic disturbance can be reduced by using individuals derived from natural populations that are close to the sites used for greening and gardening. For commercially produced individuals, genetic disturbance is unlikely in the Kanto region, an area of high usage, while genetic disturbance is thought possible in the Ryukyu Islands. Full article

Melampsora larici-populina (Mlp), M. medusae (Mmed), M. magnusiana (Mmag), and M. pruinosae (Mpr) are epidemic rust fungi in China. The first two are macrocyclic rust fungi distributed in temperate humid environments. The latter two are hemicyclic rusts, mainly distributed in arid and semi-arid areas. Ontogenetic variation that comes with this arid-resistance is of great interest—and may help us predict the influence of a warmer, drier, climate on fungal phylogeny. To compare the differences in the life history and ontogeny between the two types of rust, we cloned mating type genes, STE3.4 and STE3.3 using RACE-smart technology. Protein structures, functions, and mutant loci were compared across each species. We also used microscopy to compare visible cytological differences at each life stage for the fungal species, looking for variation in structure and developmental timing. Quantitative PCR technology was used to check the expression of nuclear fusion and division genes downstream of STE3.3 and STE3.4. Encoding amino acids of STE3.3 and STE3.4 in hemicyclic rusts are shorter than these in the macrocyclic rusts. Both STE3.3 and STE3.4 interact with a protein kinase superfamily member EGG12818 and an E3 ubiquitin protein ligase EGG09709 directly, and activating G-beta conformational changes. The mutation at site 74th amino acid in the conserved transmembrane domain of STE3.3 ascribes to a positive selection, in which alanine (Ala) is changed to phenylalanine (Phe) in hemicyclic rusts, and a mutation with Tyr lost at site 387th in STE3.4, where it is the binding site for β-D-Glucan. These mutants are speculated corresponding to the insensitivity of hemicyclic rust pheromone receptors to interact with MFa pheromones, and lead to Mnd1 unexpressed in teliospora, and they result in the diploid nuclei division failure and the sexual stage missing in the life cycle. A Phylogenic tree based on STE3.4 gene suggests these two rust types diverged about 14.36 million years ago. Although these rusts share a similar uredia and telia stage, they show markedly different wintering strategies. Hemicyclic rusts overwinter in the poplar buds endophytically, their urediniospores developing thicker cell walls. They form haustoria with a collar-like extrahaustorial membrane neck and induce host thickened callose cell walls, all ontogenetic adaptations to arid environments. Full article

Aneuploids are valuable materials of genetic diversity for genetic analysis and improvement in diverse plant species, which can be propagated mainly via in vitro culture methods. However, somaclonal variation is common in tissue culture-derived plants including euploid caladium. In the present study, the genetic stability of in vitro-propagated plants from the leaf cultures of two types of caladium (Caladium × hortulanum Birdsey) aneuploids obtained previously was analyzed morphologically, cytologically, and molecularly. Out of the randomly selected 23 and 8 plants regenerated from the diploid aneuploid SVT9 (2n = 2x − 2 = 28) and the tetraploid aneuploid SVT14 (2n = 4x − 6 = 54), respectively, 5 plants from the SVT9 and 3 plants from the SVT14 exhibited morphological differences from their corresponding parent. Stomatal analysis indicated that both the SVT9-derived variants and the SVT14-originated plants showed significant differences in stomatal guard cell length and width. In addition, the variants from the SVT14 were observed to have rounder and thicker leaves with larger stomatal guard cells and significantly reduced stomatal density compared with the regenerants of the SVT9. Amongst the established plants from the SVT9, two morphological variants containing 3.14–3.58% less mean fluorescence intensity (MFI) lost one chromosome, and four variants containing 4.55–11.02% more MFI gained one or two chromosomes. As for the plants regenerated from the SVT14, one variant with significantly higher MFI gained two chromosomes and three plants having significantly lower MFI resulted in losing four chromosomes. Three, out of the twelve, simple sequence repeat (SSR) markers identified DNA band profile changes in four variants from the SVT9, whereas no polymorphism was detected among the SVT14 and its regenerants. These results indicated that a relatively high frequency of somaclonal variation occurred in the in vitro-propagated plants from caladium aneuploids, especially for the tetraploid aneuploid caladium. Newly produced aneuploid plants are highly valuable germplasm for future genetic improvement and research in caladium. Full article