Aerial Bulbils Research Articles

Aerial bulbils as garlic alternative planting materials, a systematic review

Aerial bulbils as garlic alternative planting materials, a systematic review

Exploring the genetic diversity and population structure of aerial yams (Dioscorea bulbifera L.) DArT-seq and agronomic traits.

Dioscorea bulbifera is an edible yam specie with aerial bulbils. Assessing the genetic diversity of D. bulbifera accession for cultivation and breeding purposes is essential for it genetic improvement, especially where the crop faces minimal attention. The aims of this study was to assess the genetic diversity of Dioscorea bulbifera accessions collected from Nigeria and accessions maintained at the genebank of International Institute of Tropical Agriculture (IITA) Ibadan. Accessions were profiled using quatitative and qualitative phenotypic traits and Diversity Array Technology SNP-markers. Multivariate analysis based phenotypic traits revealed high variability among the evaluated accessions and all phenotypic traits assessed were useful in discriminating the aerial yam accessions. Clustering analysis based phenotypic traits revealed the presence of two well defined clusters. Using DArT-Seq marker, the 94 accessions were classified into three genetic group through the admixture and the phylogeny analysis. The comparision of phenotypic and genotypic clustering revealed inconsistency membership across the two clustering methods. The study established a baseline for the selection of parental lines from the genetic groups for genetic improvement of the D. bulbifera.

Anthropogenic and natural disturbances increase local genetic diversity in an early spring geophyte (Ficaria verna Huds)

AbstractThe tetraploid Ficaria verna is a common spring geophyte in central Europe and is considered invasive in the USA and Canada. It is considered an almost seed‐sterile taxon, relying on vegetative reproduction by underground tubers and aerial bulbils. Recent studies have revealed high levels of population genetic diversity in F. verna, raising the question of how genetic diversity is maintained and which factors may be responsible for the observed patterns. Polymorphic nuclear microsatellite markers were established to define multi‐locus genotypes (MLGs), to analyze fine‐scale spatial genetic structure (SGS) using grid and cross‐sampling schemes, and to quantify genetic diversity within and between nine populations with different disturbance regimes in central Germany. In total, 115 MLGs were identified among a total of 347 samples. The G/N ratio varied between 0.16 and 0.70 among populations, and in each population several unique MLGs occurred. Genotypes were highly intermingled within populations, suggesting a “guerrilla” dispersal strategy. Significant SGS (negative regression slope of kinship coefficients against inter‐individual distances) was found in four out of nine populations in fine‐scale cross‐sampling (up to 4 m) and in only one population in grid sampling (up to 14.6 m). No single MLG was found in more than one population, while many alleles were shared between populations. Within‐population clonal and allelic diversity increased with greater exposure to both anthropogenic and natural disturbances. Regular gap openings, facilitated propagule establishment, and propagule dispersal by water and mowing machines are likely important factors explaining the positive effects of disturbance on local genetic diversity of F. verna.

Comprehensive metabolite and biological profile of “Sulmona Red Garlic” ecotype’s aerial bulbils

“Sulmona Red Garlic” is a well-known Italian traditional product. Bulbs, used for culinary purposes, have been largely investigated for their medicinal properties whereas aerial bulbils are usually removed as waste material. Here, for the first time, chemical composition and biological properties of the hydroalcoholic extract from aerial bulbils were investigated. Complementary information on metabolite composition were obtained using both NMR based untargeted and HPLC-DAD targeted methodologies. The NMR analysis revealed the presence of sugars, organic acids, amino acids, organosulphur compounds (methiin, alliin, allicin and cycloalliin), and other secondary metabolites. In particular, methiin and alliin were identified for the first time in the NMR spectra of aerial bulbil garlic extracts. Polyphenol content was determined by HPLC-DAD analysis: catechin, chlorogenic acid, and gallic acid turned out to be the most abundant phenolics.Hydroalcoholic extract blocked cell proliferation of colon cancer cell line HCT116 with an IC50 of 352.07 µg/mL, while it was non-toxic to myoblast cell line C2C12. In addition, it caused seedling germination reduction of two edible and herbaceous dicotyledon species, namely Cichorium intybus and C. endivia. Moreover, the same extract reduced the gene expression of TNF-α (tumor necrosis factor), HIF1-α (hypoxia-inducible factor), VEGFA (vascular endothelial growth factor), and transient receptor potential (TRP) M8 (TRPM8) indicating the ability to contrast cancer development through the angiogenic pathway. Final, in silico experiments were also carried out supporting the biological effects of organosulphur compounds, particularly alliin, which may directly interact with TRPM8.The results here reported suggest the potential use of garlic aerial bulbils often considered a waste product as a source in phytotherapeutic remedies.

Nutritional, antinutritional and bioactivity of raw and thermal processed cultivars (five) of aerial yam bulbils

The objectives of this research were to evaluate the effect of different cooking methods (boiling, steaming and roasting) on the nutritional, antinutritional, and antioxidative potential of five aerial yam cultivars. All the chemical analyses were carried out using standard analytical methods. Steamed (1.5–3.31 g/100 g and 0.18–2.19 g/100 g) and roasted (1.53–3.20 g/100 g and 0.23–2.51 g/100 g) samples showed higher retention of fructose and glucose, respectively. Cooking decreased antinutritional contents, especially oxalate in boiled aerial yam by 26.6% (Tob2857), 30.0% (Tob3059), 10.99% (Tob3086), 21.30% (Tob3694) and 25.27% (Tob3697). Also, steamed and roasted aerial yams declined by the range 9.52–60.77% (phytate), 5.44–68.36% % (alkaloid), 13.33–44.07% (tannin), and 17.53–68.35% (phenol), when compared to raw aerial yam. The DPPH activities increased significantly after all cooking processes. Roasted aerial yam had the highest (40.24–52.15%) DPPH activity, followed by boiled (33.86–51.65%) and steamed (29.13–45.42%) aerial yam. On the other hand, raw aerial yam had higher FRAP content than cooked aerial yam. Cooked aerial bulbils are reliable nutritional sources with high retention of fibre and DPPH and low sugar contents suitable for good health.

Transcriptomic analysis of Chinese yam (Dioscorea polystachya Turcz.) variants indicates brassinosteroid involvement in tuber development.

Dioscorea is an important but underutilized genus of flowering plants that grows predominantly in tropical and subtropical regions. Several species, known as yam, develop large underground tubers and aerial bulbils that are used as food. The Chinese yam (D. polystachya Turcz.) is one of the few Dioscorea species that grows well in temperate regions and has been proposed as a climate-resilient crop to enhance food security in Europe. However, the fragile, club-like tubers are unsuitable for mechanical harvesting, which is facilitated by shorter and thicker storage organs. Brassinosteroids (BRs) play a key role in plant cell division, cell elongation and proliferation, as well as in the gravitropic response. We collected RNA-Seq data from the head, middle and tip of two tuber shape variants: F60 (long, thin) and F2000 (short, thick). Comparative transcriptome analysis of F60 vs. F2000 revealed 30,229 differentially expressed genes (DEGs), 1,393 of which were differentially expressed in the growing tip. Several DEGs are involved in steroid/BR biosynthesis or signaling, or may be regulated by BRs. The quantification of endogenous BRs revealed higher levels of castasterone (CS), 28-norCS, 28-homoCS and brassinolide in F2000 compared to F60 tubers. The highest BR levels were detected in the growing tip, and CS was the most abundant (439.6 ± 196.41 pmol/g in F2000 and 365.6 ± 112.78 pmol/g in F60). Exogenous 24-epi-brassinolide (epi-BL) treatment (20 nM) in an aeroponic system significantly increased the width-to-length ratio (0.045 ± 0.002) compared to the mock-treated plants (0.03 ± 0.002) after 7 weeks, indicating that exogenous epi-BL produces shorter and thicker tubers. In this study we demonstrate the role of BRs in D. polystachya tuber shape, providing insight into the role of plant hormones in yam storage organ development. We found that BRs can influence tuber shape in Chinese yam by regulating the expression of genes involved cell expansion. Our data can help to improve the efficiency of Chinese yam cultivation, which could provide an alternative food source and thus contribute to future food security in Europe.

Full-length transcriptome-referenced analysis reveals crucial roles of hormone and wounding during induction of aerial bulbils in lily

Aerial bulbils are important vegetative reproductive organs in Lilium. They are often perpetually dormant in most Lilium species, and little is known about the induction of these vegetative structures. The world-famous Oriental hybrid lily cultivar ‘Sorbonne’, which blooms naturally devoid of aerial bulbils, is known for its lovely appearance and sweet fragrance. We found that decapitation stimulated the outgrowth of aerial bulbils at lower stems (LSs) and then application of low and high concentrations of IAA promoted aerial bulbils emergence around the wound at upper stems (USs) of ‘Sorbonne’. However, the genetic basis of aerial bulbil induction is still unclear. Herein, ‘Sorbonne’ transcriptome has been sequenced for the first time using the combination of third-generation long-read and next-generation short-read technology. A total of 46,557 high-quality non-redundant full-length transcripts were generated. Transcriptomic profiling was performed on seven tissues and stems with treatments of decapitation and application of low and high concentrations of IAA, respectively. Functional annotation of 1918 DEGs within stem samples of different treatments showed that hormone signaling, sugar metabolism and wound-induced genes were crucial to bulbils outgrowth. The expression pattern of auxin-, shoot branching hormone-, plant defense hormone- and wound-inducing-related genes indicated their crucial roles in bulbil induction. Then we established five hormone- and wounding-regulated co-expression modules and identified some candidate transcriptional factors, such as MYB, bZIP, and bHLH, that may function in inducing bulbils. High connectivity was observed among hormone signaling genes, wound-induced genes, and some transcriptional factors, suggesting wound- and hormone-invoked signals exhibit extensive cross-talk and regulate bulbil initiation-associated genes via multilayered regulatory cascades. We propose that the induction of aerial bulbils at LSs after decapitation can be explained as the release of apical dominance. In contrast, the induction of aerial bulbils at the cut surface of USs after IAA application occurs via a process similar to callus formation. This study provides abundant candidate genes that will deepen our understanding of the regulation of bulbil outgrowth, paving the way for further molecular breeding of lily.

Propagation and control of Anredera cordifolia (Ten.) Stennis (madeira vine)

Anredera cordifolia (Ten.) Stennis, commonly known as the madeira vine, is a succulent vine that produces vegetative structures on stems and invades agricultural areas in Brazil. This plant has become a possible invader in Brazilian agriculture with records of losses in coffee crops. The objective of this study was to study the influence of dimensional variation and different depths of planting aerial bulbils on the growth and development of A. cordifolia plants, as well as to study the influence of the effect of herbicides on postemergence control. All experiments were carried out in a greenhouse. In the propagation experiment, a completely randomized design with six replications was used. Aerial tubers of four weight categories (C) (C1, 0–0.59 g; C2, 0.60–1.49 g; C3, 1.50–2.99 g; C4, 3.0–12.0 g) were evaluated regarding the percentage of viable tubers, number of stems per tuber (ST), average stem length, shoot dry matter, and emergence speed index (ESI). ST and ESI were evaluated at seven soil depths (0, 3, 6, 10, 15, 20, and 30 cm). For experiments with herbicides, a completely randomized design with four replications was used. Six herbicides (chlorimuron-ethyl, flumioxazin, glyphosate, metsulfuron-methyl, saflufenacil, and glyphosate + saflufenacil) at the recommended doses and a control (without herbicide) were used to evaluate the postemergence control. Plants from larger tubers had a higher sprouting rate and faster growth and establishment, and tubers grown on the soil surface produced plants with faster development. Glyphosate + saflufenacil was more effective in controlling this plant species, with 79.50% control. All other herbicide treatments caused only chlorosis and poor control.

Antimicrobial potential of silver nanoparticles biosynthesized using aerial yam bulbils for control of selected phytopathogens

Silver nanoparticles as antimicrobial agent have vast potential in agriculture for the protection of plants from diseases and increasing crop productivity. In this study, the bulbils of aerial yam (Dioscorea bulbifera L.) were investigated for their potential for biosynthesis of silver nanoparticles. Variation in the absorption spectra of silver nanoparticles synthesized using different concentrations of 10 to 50% (v/v) of plant extract was observed. Phytochemical analysis of aerial yam bulbils revealed high content of flavonoid (4.06 ± 0.44 mg/g), phenols (3.36 ± 0.20 mg/g) and tannins (12.42 ± 0.22 mg/g) with potential role in the bioreduction process. Highest inhibition (98-100%) was recorded against Fusarium oxysporum and Colletotrichum gloeosporioides with 100 ppm silver nanoparticles. The inhibition zone against Bacillus sp. and Enterobacter cloacae ranged from 6.00 ± 0.41 to 11.00 ± 0.87 mm at 100 ppm concentration indicating antibacterial efficacy of biosynthesized silver nanoparticles. Silver nanoparticles biosynthesized using 20% (v/v) extract at higher temperature demonstrated the most effective inhibition of plant pathogenic fungi and bacteria.

Patterns of transmission and horizontal gene transfer in the Dioscorea sansibarensis leaf symbiosis revealed by whole-genome sequencing

Leaves of the wild yam species Dioscorea sansibarensis display prominent forerunner or "drip" tips filled with extracellular bacteria of the species Orrella dioscoreae.1 This species of yam is native to Madagascar and tropical Africa and reproduces mainly asexually through aerial bulbils and underground tubers, which also contain a small population of O.dioscoreae.2,3 Despite apparent vertical transmission, the genome of O.dioscoreae does not show any of the hallmarks of genome erosion often found in hereditary symbionts (e.g., small genome size and accumulation of pseudogenes).4-6 We investigated here the range and distribution of leaf symbiosis between D.sansibarensis and O.dioscoreae using preserved leaf samples from herbarium collections that were originally collected from various locations in Africa. We recovered DNA from the extracellular symbiont in all samples, showing that the symbiosis is widespread throughout continental Africa and Madagascar. Despite the degraded nature of this DNA, we constructed 17 symbiont genomes using de novo methods without relying on a reference. Phylogenetic and genomic analyses revealed that horizontal transmission of symbionts and horizontal gene transfer have shaped the evolution of the symbiont. These mechanisms could help explain lack of signs of reductive genome evolution despite an obligate host-associated lifestyle. Furthermore, phylogenetic analysis of D.sansibarensis based on plastid genomes revealed a strong geographical clustering of samples and provided evidence that the symbiosis originated at least 13 mya, earlier than previously estimated.3.

Phenological synchrony between a weed (Dioscorea bulbifera) and a biocontrol agent (Lilioceris cheni) in the introduced range, Florida: implications for biological control

ABSTRACT Dioscorea bulbifera has invaded, smothered, and disrupted ecological functions of native plant communities in Florida. Vines senesce in late fall, then overwinter as tubers and aerial bulbils which sprout in spring and repeat the growth cycle. A foliage-feeding beetle Lilioceris cheni, introduced from Asia as a biocontrol agent has established throughout D. bulbifera's range in Florida. Synchronies among the growth phenology of the weed, life stages of biocontrol agents and weather conditions, are considered essential for the successful suppression of an introduced weed. We conducted a common garden study that encompassed pre-biocontrol release attributes of D. bulbifera followed by a 5-yr post-L. cheni release impacts study on its natural infestations in four sites. We gathered monthly data on D. bulbifera and L. cheni and assessed possible synchronies between their life stages and with local weather variables. Air and soil temperatures and total rainfall showed positive correlation with timing of D. bulbifera vine emergence/senescence, vine coverage, adult beetle emergence from diapause, and their life stages (egg clutches, larvae, and adults). Vine sprouting and beetle emergence in two southern sites began in February and April, and in the remaining two northern sites in March and May, respectively. Vine sprouting and beetle emergence was initiated at 15 and 20°C, respectively. All sites achieved maximum vine coverage in July. Bulbil development, oviposition by overwintering adults, and vine damage by adult and larval feeding began in June. These sequences of events indicated phenological synchrony of the beetle and air potato life stages in Florida.

Allometric equations for the invasive vine air potato (Dioscorea bulbifera) in its exotic range in Florida

AbstractNondestructive means for estimating air potato (also known as air yam; Dioscorea bulbifera L.) biomass will help gauge its management efficacy over time. We developed allometric equations to estimate total and fractional biomass components and densities of aerial bulbils and underground tubers of field-grown D. bulbifera in Florida. We selected four naturally infested sites representing its southern, central, and northern distribution in Florida and measured three independent variables (vine densities, stem diameters, and top heights) of 84 (21 site−1) discrete D. bulbifera patches during late October to early December of 2012. We destructively harvested D. bulbifera biomass, sorted by tubers, stems, leaves, and bulbils; counted units of bulbils and underground tubers (dependent variables); and dried to a constant weight. Mean percentages of tuber, stem, leaf, and bulbil fractions in total biomass were 42.0, 15.6, 26.0, and 16.4, respectively. We developed a parameterized multiplicative prediction model and regression equation for each dependent variable. Slopes of relationships among independent and dependent variables varied by biomass and density (bulbil and tuber) of plant components. Multiplied values of independent variables: all three for total, tuber, stem, and leaf biomass; two (vine base diameter*patch height) for bulbil biomass; two (vine density*patch height) for bulbil density; and only one (stem density) for tuber density provided best (R2-based) prediction values. These models will provide nondestructive methods for estimating biomass components and density of vegetative propagules of naturally growing D. bulbifera. Models are critical for understanding the performance of D. bulbifera in its exotic range, estimating biomass to project control costs, and comparing biomass components and bulbil/tuber densities during pre- and postmanagement periods to gauge control efficacy.

Cloning and expression analysis of LoCCD8 during IAA-induced bulbils outgrowth in lily (Oriental Hybrid ‘Sorbonne’)

Aerial bulbils, which resemble tiny bulbs, develop from axillary buds and facilitate rapid propagation of Lilium. In most species of lily, bulbils are perpetually dormant and little is known about induction of these vegetative structures. Herein, we proposed that strigolactones (SLs) may regulate the induction of bulbils in Lilium. We tested this hypothesis by isolating and investigating the expression patterns of 2 copies of the carotenoid cleavage dioxygenase8 (CCD8) gene in lily—LoCCD8a and LoCCD8b—with regard to biosynthesis of SLs. Expression analyses revealed that LoCCD8a principally is expressed during vegetative growth, whereas LoCCD8b mainly is expressed during reproductive growth. The maximum quantity of LoCCD8a transcripts was observed in the basal plate in most developmental stages, which suggests that SLs may originate from underground parts, especially the basal plate, and move upward. The effects of treatments with indole-3-acetic acid or SL analog (GR24) on outgrowth of bulbils and expression of LoCCD8 genes suggested that SLs function downstream of auxin to inhibit the outgrowth of bulbil. The expression patterns of LoCCD8a and LoCCD8b at sprouting and bulblet weighting stages also implied that SLs may function in nutrient redistribution. Our findings are expected to promote the utilization of bulbils as vegetative propagules for commercial practice.

Histological and Transcriptomic Analysis during Bulbil Formation in Lilium lancifolium.

Aerial bulbils are an important propagative organ, playing an important role in population expansion. However, the detailed gene regulatory patterns and molecular mechanism underlying bulbil formation remain unclear. Triploid Lilium lancifolium, which develops many aerial bulbils on the leaf axils of middle-upper stem, is a useful species for investigating bulbil formation. To investigate the mechanism of bulbil formation in triploid L. lancifolium, we performed histological and transcriptomic analyses using samples of leaf axils located in the upper and lower stem of triploid L. lancifolium during bulbil formation. Histological results indicated that the bulbils of triploid L. lancifolium are derived from axillary meristems that initiate de novo from cells on the adaxial side of the petiole base. Transcriptomic analysis generated ~650 million high-quality reads and 11,871 differentially expressed genes (DEGs). Functional analysis showed that the DEGs were significantly enriched in starch and sucrose metabolism and plant hormone signal transduction. Starch synthesis and accumulation likely promoted the initiation of upper bulbils in triploid L. lancifolium. Hormone-associated pathways exhibited distinct patterns of change in each sample. Auxin likely promoted the initiation of bulbils and then inhibited further bulbil formation. High biosynthesis and low degradation of cytokinin might have led to bulbil formation in the upper leaf axil. The present study achieved a global transcriptomic analysis focused on gene expression changes and pathways' enrichment during upper bulbil formation in triploid L. lancifolium, laying a solid foundation for future molecular studies on bulbil formation.

Allium pseudotelmatum (Amaryllidaceae), a new species of Allium sect. Codonoprasum from Croatia

Allium pseudotelmatum, a new species of A. sect. Codonoprasum, is described from the southern Dalmatia (Croatia). It is a late-summer flowering species with pentaploid (2n = 40) chromosome complement, occurring in synanthropic habitats (Citrus orchards with nutrient rich and fresh moist soil). Karyology, leaf anatomy, morphology, ecology, molecular (ITS) and taxonomic relationships with related species are examined for the species. It shows morphological relationships with the northern Dalmatian species A. telmatum from which it well differentiates for many morphological characters including the presence of aerial bulbils within the inflorescence, phenology, chromosome number and ecology. Confusion of A. pseudotelmatum with some specimens of A. oleraceum due to the presence of bulbils within the inflorescence is discussed.

Causes of variation in sexual and asexual reproduction in diploid and triploid populations of Allium scorodoprasum

Allium scorodoprasum is a bulbous geophyte that reproduces by seeds, aerial bulbils, and subterranean daughter bulbs. This research represents the analysis of intraspecific variations in sexual and asexual reproduction in relation to ploidy levels and the environmental conditions from 11 diploid and 24 triploid populations in Lithuania. The results showed that the seed production was extremely rare and occurred only in diploid populations. The numbers of flowers and aerial bulbils per plant as well as mean mass of one bulbil were the characteristics in which differences between ploidy levels were the biggest. The diploids on average produced more (61.9), but smaller (mean mass = 29.6 mg) bulbils and more flowers (16.7), while triploids produced less (41.7), but larger (mean mass = 45.9 mg) bulbils and fewer (5.2) flowers. The study revealed that the main determinant of intracytotypic variation in quantity of both sexual and asexual structures was light availability.

Wild food plants and fungi used in the mycophilous Tibetan community of Zhagana (Tewo County, Gansu, China).

BackgroundThe aim of the study was to investigate knowledge and use of wild food plants and fungi in a highland valley in the Gannan Tibetan Autonomous Region on the north-eastern edges of the Tibetan Plateau.MethodsField research was carried out in four neighbouring villages in a mountain valley of the Diebu (Tewo) county, surrounded by spruce forests. The study consisted of 30 interviews with single informants, or group interviews (altogether 63 informants). Apart from collecting voucher specimens, we also identified fungi using DNA barcoding.ResultsWe recorded the use of 54 species of vascular plants. We also recorded the use of 22 mushroom taxa, which made up the largest category of wild foods. Fruits formed the largest category of food plants, with 21 species, larger than the wild greens category, which consisted of 20 species eaten after boiling or frying and 7 as raw snacks. We also recorded the alimentary use of 10 species of edible flowers and 3 species with underground edible organs. On average, 20.8 edible taxa were listed per interview (median – 21). The most listed category of wild foods was green vegetables (mean – 7.5 species, median – 8 species), but fruits and mushrooms were listed nearly as frequently (mean – 6.3, median – 6 and mean – 5.8, − median 6 respectively). Other category lists were very short, e.g., flowers (mean – 1.3, median – 1) and underground edible parts (mean – 0.7, median – 1).Wild vegetables are usually boiled and/or fried and served as side-dishes, or their green parts are eaten as snacks during mountain treks (e.g., peeled rhubarb shoots). Wild fruits are mainly collected by children and eaten raw, they are not stored for further use. The most widely used wild staple foods are Potetilla anserina roots, an important ceremonial food served on such occasions as New Year or at funerals. They are boiled and served with sugar and butter. The most important famine plants remembered by people are the aerial bulbils of Persicaria vivipara. Flowers are used as children’s snacks – their nectar is sucked.ConclusionsThe number of wild taxa eaten in the studied valley is similar to that of other Tibetan areas. The structure of wild food plant taxa is also very typical for Tibetan speaking areas (e.g., the use of rhubarb shoots, Potentilla anserina, Persicaria vivipara). The studied community show a high level of mycophilia.

Population genetic structure and clonal diversity of Allium oleraceum (Amaryllidaceae), a polyploid geophyte with common asexual but variable sexual reproduction

Clonal plants are, on average, considered to be as genetically diverse as nonclonal plants. However, the behaviour of clonal plants ranges between multiclonality and uniclonality, depending on environmental conditions and life history traits. Allozyme electrophoresis of band phenotypes was used to examine the genetic structure of 13 cytotype-uniform and 17 cytotype-mixed populations of polyploid Allium oleraceum (2n = 4x, 5x, 6x), a clonal bulbous geophyte that has been considered seed-sterile and completely reliant on vegetative reproduction through aerial bulbils and daughter bulbs. The genetic structure was dominated by low within-population variation whereas genetic differentiation was high among populations. Eighty-five distinct multilocus genotypes were found among 756 sampled individuals, but populations generally exhibited a low level of clonal diversity. Tetra- and pentaploids showed twofold higher total and within-population diversity, but also had more genetically differentiated populations in comparison with hexaploids. Tetraploids formed two separate groups in the cluster analysis, and this finding most likely suggests their different origin. Pentaploids were grouped in a separate cluster and frequently intermixed with tetra- and hexaploids sampled at cytotype-mixed sites. Such a pattern suggests gene flow between cytotypes. Most hexaploids were genetically similar and clustered separately from the other cytotypes, suggesting their similar origin and absence of gene flow to and from other cytotypes. Identical band phenotypes found in coexisting cytotypes within certain mixed-ploidy populations might indicate in situ neopolyploidization. Collectively, the pattern of genetic structure and diversity observed in A. oleraceum is typical of clonal plants with the dominance of vegetative offspring and scarce recruitment of sexual offspring. The low and spatially unstructured genetic variation observed in hexaploids, in contrast with higher and spatially structured genetic variation in tetra- and pentaploids, seems to be related to different levels of sexual fertility, ecological amplitude and colonization abilities of the cytotypes. It provides evidence for the existence of both primary and secondary contact zones of cytotypes in A. oleraceum.

Bulbilhos aéreos de alho, provenientes de escapes florais, são infectados por vírus

Em campos de produção comercial de alho é comum observar plantas naturalmente infectadas por vírus dos gêneros Allexivirus, Carlavirus e Potyvirus. Os bulbilhos aéreos podem ser uma alternativa para a propagação de plantas de alho livres de vírus. Desta forma, o objetivo deste trabalho foi analisar a taxa de perpetuação dos vírus de plantas infectadas para os bulbilhos aéreos. Os bulbilhos aéreos obtidos de plantas infectadas foram analisados por RT-PCR utilizando oligonucleotídeos universais para os gêneros Allexivirus, Carlavirus e Potyvirus. A taxa de perpetuação foi de 65% para allexivírus, 20% para carlavírus e 82,22% para potyvírus. Os resultados demonstraram que a perpetuação dos diferentes vírus do bulbo para os bulbilhos aéreos é elevada, inviabilizando a utilização direta dos bulbilhos aéreos provenientes de plantas matrizes infectadas por vírus. Esta metodologia deve ser utilizada somente a partir de plantas isentas de vírus.

Biology of the polyploid geophyte Allium oleraceum (Amaryllidaceae): Variation in size, sexual and asexual reproduction and germination within and between tetra-, penta- and hexaploid cytotypes

It has been proposed that plant species cytotypes commonly exhibit altered morphology, reproduction, geographic and ecological distributions. We studied phenotypic variation in height, sexual (flowers, seeds) and asexual (aerial bulbils) reproduction in natural populations and in the conditions of a common garden of three cytotypes (2n=4x, 5x, 6x) of the bulbous geophyte Allium oleraceum in the Czech Republic. Additionally, we compared the germination and dormancy of seeds and bulbils to determine whether propagules have different ecological roles. The pattern of morphological differentiation observed between cytotypes under natural conditions was similar to that observed under common garden conditions, suggesting that variability in morphological characteristics appears to be associated with ploidy levels. We revealed differences in size and sexual and asexual production between A. oleraceum cytotypes, but with wide overlap among cytotypes, suggesting a limited possibility of the studied traits to reliably distinguish between cytotypes. Tetraploids and pentaploids were rather similar; they were taller and produced more flowers than hexaploids, which were mostly flowerless (mean <0.7 flower/plant). All cytotypes were able to produce viable seeds, but their numbers were extremely low, usually less than 3 seeds per inflorescence; clonal reproduction via aerial bulbils dominates in all cytotypes (flower:bulbil ratio <0.5), with tetraploids producing more but lighter bulbils than other cytotypes. The seed: ovule ratio was low (<0.1) in all cytotypes, although hexaploids reached higher values than other cytotypes. Bulbils germinated better (means >80%) than seeds in all cytotypes, with pentaploid bulbils showing the highest germination (mean 90.5%). The cytotypes did not differ in seed germination (range of means 73.4%–76.3%). About 6% of seeds did not germinate but were still viable at the end of the experiment, while all non-germinated bulbils of all cytotypes had rotten away. Seeds, but not bulbils, can likely form a short-term persistent propagule soil bank. We found no evidence of a phenotypic trade-off between the production of flowers (seeds) and the production of bulbils within the inflorescence of all studied cytotypes. Together, inter-cytotypic differences in fitness-related traits cannot completely explain the different geographic and ecological distributions of cytotypes in the Czech Republic found by previous research.