Daucus Species Research Articles

Evaluating aggressiveness and host range of Alternaria dauci in a controlled environment

The aggressiveness of Alternaria dauci isolates was investigated in greenhouse conditions. Twenty‐seven isolates were pre‐selected from a large collection to represent high diversity according to geographic or host origins and intergenic spacer (IGS) polymorphism. IGS sequence analysis revealed that isolates were grouped within three different clusters. Eleven isolates were selected and inoculated on a susceptible carrot cultivar. Three criteria (mean lesion number, mean necrotic leaf area and mean disease index) were used to assess the aggressiveness of isolates. Continuous variation in aggressiveness was shown and no clear division into isolate classes was evident. For the host range study, two isolates were inoculated under greenhouse conditions onto nine cultivated Apiaceae species, two wild Daucus species and six cultivated non‐Apiaceae species representing six botanical families. Lesions varying in severity were observed on all dicot species (Apiaceae and non‐Apiaceae), but no symptoms developed on the two monocots studied (leek and sweetcorn). Plant species were also differentiated on the basis of expanding lesions (cultivated and wild carrot, dill and fennel) or non‐expanding lesions (other dicot species). Typical A. dauci conidia were observed after in vitro incubation of leaves with symptoms. Fungal structures were isolated from lesions and A. dauci was confirmed on the basis of conidial morphology and specific conventional PCR results. Genotyping of individual isolates performed with microsatellite markers confirmed the presence of the inoculated isolate. The results clearly showed that, in controlled conditions, the host range of A. dauci is not restricted to carrot.

A Myristicin-rich Essential Oil from Daucus Sahariensis Growing in Algeria

The essential oils obtained by hydrodistillation from leaves and fruits of Daucus sahariensis Murb. were analyzed by GC/MS. The main constituents of the essential oil from the leaves were myristicin (34.3%), alpha-pinene (5.4%), cis-chrysanthenyl acetate (5.3%) and epi-alpha-bisabolol (4.8%), and those from the fruits myristicin (43.9%), alpha-pinene (13.1%), limonene (9.4%), and cis-chrysanthenyl acetate (7.4%). Myristicin, the main constituent of both essential oils, is generally absent in the oils from other Daucus species, permitting the hypothesis that this compound is a chemical marker of this Saharan species.

Comparative FISH mapping of Daucus species (Apiaceae family)

The cytogenetic characterization of the carrot genome (Daucus carota L., 2n = 18) has been limited so far, partly because of its somatic chromosome morphology and scant of chromosome markers. Here, we integrate the carrot linkage groups with pachytene chromosomes by fluorescent in situ hybridization (FISH) mapping genetically anchored bacterial artificial chromosomes (BACs). We isolated a satellite repeat from the centromeric regions of the carrot chromosomes, which facilitated the study of the pachytene-based karyotype and demonstrated that heterochromatic domains were mainly confined to the pericentromeric regions of each chromosome. Chromosome-specific BACs were used to: (1) physically locate genetically unanchored DNA sequences, (2) reveal relationships between genetic and physical distances, and (3) address chromosome evolution in Daucus. Most carrot BACs generated distinct FISH signals in 22-chromosome Daucus species, providing evidence for syntenic chromosome segments and rearrangements among them. These results provide a foundation for further cytogenetic characterization and chromosome evolution studies in Daucus.

Major cytogenetic landmarks and karyotype analysis inDaucus carota and other Apiaceae

Karyotype analysis provides insights into genome organization at the chromosome level and into chromosome evolution. Chromosomes were marked for comparative karyotype analysis using FISH localization of rDNA genes for the first time in Apioideae species including taxa of economic importance and several wild Daucus relatives. Interestingly, Daucus species did not vary in number of rDNA loci despite variation in chromosome number (2n = 18, 20, 22, and 44) and previous publications suggesting multiple loci. All had single loci for both 5S and 18S-25S (nucleolar organizing region) rDNA, located on two different chromosome pairs. The 5S rDNA was on the short arm of a metacentric chromosome pair in D. crinitus (2n = 22) and D. glochidiatus (2n = 44) and on the long arm of a metacentric pair in other Daucus species, suggesting possible rearrangement of this chromosome. For other Apiaceae, from two (Apium graveolens), to three (Orlaya grandiflora), to four (Cuminum cyminum) chromosomes had 18S-25S rDNA sites. Variability for number and position of the 5S rDNA was also observed. FISH signals enabled us to identify 20-40% of the chromosome complement among species examined. Comparative karyotype analysis provides insights into the fundamental aspects of chromosome evolution in Daucus.

Characterization and distribution of Daucus species in Syria

Syria is considered as one of the important centres for Daucus diversity including Daucus carota. Therefore, it is essential to study the distribution and characterization of these species in Syria. An exploration of plants belonging to the Apiaceae family was conducted on road and field sides in several areas of Syria. Seeds (fruits) from these plants have been also collected. The seeds were sown in pots containing peatmoss in a glasshouse and emerging plants were grown until flowering and seed formation. The plants were classified based on leaf, umbel, and seed shape. Proteins were extracted from the leaves and analysed using electrophoresis to establish genetic relationships among species. Seven Daucus species have been identified to grow in Syria. These are D. aureus, D. bicolor, D. carota, D. durieua, D. guttatus, D. littoralis, and D. muricatus. Isozyme and total protein analysis, cluster analysis, and correlation matrix have revealed considerable genetic variation among studied Daucus species. Wild carrot (D. carota) came in one group with its cultivated form (D. carota ssp. sativus) and the closest species to them was D. guttatus. Species D. bicolor and D. durieua were in the same group and D. aureus and D. littoralis were in another group farther from the previous groups. The farthest species on the genetic tree was D. muricatus.

Intercontinental disjunctions in Cryptotaenia (Apiaceae, Oenantheae): an appraisal using molecular data

AbstractAim The angiosperm genus Cryptotaenia (family Apiaceae, tribe Oenantheae) exhibits an anomalous distribution pattern, with five of its eight species being narrow endemics geographically isolated from their presumed relatives. We examined the monophyly of the genus and ascertained the phylogenetic placements of its constituent members in order to explain their distribution patterns.Location Eastern North America, eastern Asia, the Caucasus, southern Italy, Macaronesia and Africa.Methods In total, 173 accessions were examined for nuclear rDNA ITS sequence variation, representing nearly all major lineages of Apiaceae subfamily Apioideae and seven species of Cryptotaenia. Sampling of tribes Oenantheae, Scandiceae and Pimpinelleae was comprehensive. Phylogenetic analyses included Bayesian, maximum parsimony and neighbour‐joining methods; biogeographical scenarios were inferred using dispersal–vicariance analysis (diva).Results Cryptotaenia is polyphyletic and includes three distant lineages. (1) Cryptotaenia sensu stricto (C. canadensis, C. japonica, C. flahaultii and C. thomasii) is maintained within tribe Oenantheae; C. canadensis and C. japonica, representing an eastern North American–eastern Asian disjunction pattern, are confirmed to be sister species. (2) Cryptotaenia elegans, endemic to the Canary Islands, is placed within Scandiceae subtribe Daucinae along with two woody endemics of Madeira, Monizia edulis and Melanoselinum decipiens. The phylogeny of these Canarian and Madeiran endemics is unresolved. Either they constitute a monophyletic sister group to a clade comprising some Mediterranean and African species of Daucus and their relatives, or they are paraphyletic to this clade. The herbaceous/woody genus Tornabenea from Cape Verde, once included in Melanoselinum, is not closely related to the other Macaronesian endemics but to Daucus carota. (3) The African members of Cryptotaenia (C. africana, C. calycina and possibly C. polygama) comprise a clade with some African and Madagascan umbellifers; this entire clade is sister group to Eurasian Pimpinella.Main conclusions Elucidating the phylogeny of the biogeographically anomalous Cryptotaenia sensu lato enabled hypotheses on the biogeography of its constituent lineages. Cryptotaenia sensu stricto exhibits a holarctic distribution pattern, with its members occurring in regions that were important glacial refugia. The genus probably originated in eastern Asia and from there dispersed to Europe and North America. For the Macaronesian endemic species –C. elegans, M. edulis and M. decipiens–diva reconstructs either a single dispersal event to Macaronesia from the Mediterranean/African region, or a single dispersal followed by a back‐dispersal to the mainland. The radiation of Tornabenea from Cape Verde followed a second dispersal of Daucinae to Macaronesia. Woodiness in Melanoselinum/Monizia and Tornabenea, therefore, is a derived and independently acquired trait. The African members of Cryptotaenia are derived from an ancestor arriving from the Middle East.

Geographical distribution of wild Daucus species in the natural grasslands of the Argentinian pampas

Three wild carrot species have been reported in the argentinian flora: Daucus montanus Humb. et Bonpl. ex Schult., D. montevidensis Link ex Sprengel and D. pusillus Michx. There is a discrepancy among authors about the distinctive morphological traits of the last two species; thus, it is difficult to ascertain if they are truly two distinct taxa. Based on the available literature and in the search of a paradigmatic site, four collection trips were carried out in 2004 and 2005 in Buenos Aires and Southern Entre Rios provinces. Populations were sampled at 30 sites, and local environmental parameters and associated plant species were recorded. Morphological observations and chromosome counts were carried out on 10 plants/population. Three morphological phenotypes were distinguished: one in 18 populations, all with 2n = 2x = 18, and two in the remaining 12, with 2n = 2x = 22 or aneusomaty (2n = 2x = 20, 22). Populations of the first phenotype were assigned to wild D. carota and the rest, tentatively, to D. pusillus (D. montevidensis?), till further evaluations are carried out in test sites to verify this tentative conclusion.

First report of Rhizoctonia zeae on Lolium perenne and Festuca sp. in Hungary

In August 2002, brown patches were observed on turf grasses in parks and gardens at four locations in Budapest. Twenty-five samples of Lolium perenne and Festuca sp. showing disease symptoms were collected. The symptoms observed were necrotic lesions on the roots and stems, as well as brown lesions on the leaves. Small pieces of infected tissues were surface sterilized and incubated at 22°C with a 12 h photoperiod on potato dextrose agar. In most cases fast-growing, buff-coloured colonies were observed, with dark brown sclerotia of irregular shape, not differentiated into a rind and medulla, with a size range of 0·2–3·0 mm. These were identified as Rhizoctonia solani (Sneh et al., 1991; Roberts, 1999). Colonies from three samples were colourless to buff-coloured, fast-growing, with small, ball-shaped, reddish-coloured sclerotia 0·5–0·9 mm in diameter. These were identified as Rhizoctonia zeae (Sneh et al., 1991; Roberts, 1999). The hyphae of both types of isolate were multiseptate and multinucleate (confirmed by nuclear staining). The pathogenicity of one R. zeae isolate was determined on a mixture of L. perenne, Festuca rubra and Poa pratensis seedlings. Sterilized barley seeds, colonised with R. zeae and covered with pinkish to orange sclerotia of 0·5–2·5 mm diameter, were used as inoculum. Seeds of test plants were sown in a sandy loam soil admixed with barley seeds previously infected with the pathogen. Pots were then maintained in a glasshouse kept at 16–32°C. Disease symptoms were observed 3 weeks after germination. Brownish lesions were observed on infected seedlings at the base of stems and the lower parts of the leaves. Infected roots showed brown lesions and the leaves, on which orange sclerotia were found, were necrotic. Control plants grown in pots with uninoculated soil did not develop symptoms. Rhizoctonia zeae was reisolated from the diseased tissues. In a host-range study, the isolate proved to be highly pathogenic to germlings of several ornamental and cultivated plants, including Beta vulgaris ssp. vulgaris, Callistephus sinensis, Dahlia variabilis, Daucus carota, Lupinus polyphyllus, Papaver somniferum, Pennisetum glaucum, Phaseolus vulgaris, Sesamum indicum, Solanum melongena, Solanum tuberosum, Sorghum bicolor and Triticum aestivum. The disease caused by R. zeae was described for the first time in Florida, by Voorhees (1934), as sclerotial rot of corn. This fungus is distributed in temperate regions, causing diseases on many plants including species of Agrostis, Beta, Cucumis, Daucus, Festuca, Helianthus, Oryza, Sorghum, Triticum and Zea. This is the first report of R. zeae in Hungary. This work is a part of a study supported by grant NKFP 4/008/2001.

Further studies on Carrot virus Y: hosts, symptomatology, search for resistance, and tests for seed transmissibility

Carrot virus Y (CarVY) was studied to provide information on its host range and symptoms, identify any alternative natural hosts and sources of host resistance in carrot germplasm, and determine whether it is seed-borne. Twenty-two species belonging to the Apiaceae were inoculated with CarVY by viruliferous aphids in the glasshouse. Systemic infection with CarVY developed in carrot itself, 4 other Daucus species, 5 herbs, 1 naturalised weed, and 2 Australian native plants. When 7 of these host species were exposed to infection in the field, all became infected systemically. In both glasshouse and field, the types of symptoms that developed in infected plants and their severity varied widely from host to host. Following inoculation with infective sap, the virus was detected in inoculated leaves of 1 additional species in the Apiacaeae, and 2 species of Chenopodiaceae. A field survey did not reveal any alternative hosts likely to be important as CarVY infection reservoirs. When 34 accessions of wild carrot germplasm and 16 of other Daucus spp. were inoculated with infective aphids, symptom severity varied widely among accessions but no source of extreme resistance to CarVY was found. Tests on seedlings grown from seed collected from individual infected plants or field plantings (most with CarVY incidences of >92%) of cultivated carrot (34 135 seeds), wild carrot (20 978 seeds), Anethum graveolens (22 921 seeds), and 3 other host species (3304 seeds) did not detect any seed transmission of CarVY. The implications of these results for control of the virus in carrot crops, minimising the losses it causes, and avoiding its introduction to new locations are discussed.

A taxonomic study on Daucus species vegetated in islands off the Korean Peninsula

Daucus species vegetated in the island Dae-heug-san-do off the Korean Peninsula has been recorded as Daucus littoralis Sibth. et Sm. var. koreana Nakai, endemic to Korea in several flora. However, the name was revealed as a naked name, nomen nudum, because the valid publication and type specimens were found anywhere. Comparative observation on morphological characters between the Korean taxon of Daucus and D. littoralis reveals that the Korean vegetated in the island Dae-heug-san-do is not the D. littoralis, but the D. carota L. subsp. carota. The Korean name of the latter is designated newly as San-dang-geun. The new korean name, Seon-dang-geun, of the unrecorded taxon, D. carota subsp. maritimus (Lam.) Batt., is also given.

Essential Oil of Daucus glaber Forssk

The composition of the essential oil of the fruits, leaves and stems of Daucus glaber Forssk has been studied by GC/MS. It was found that, the essential oil of the fruits consists of monoterpene hydrocarbons (limonene and sylvestrene are the majors) and phenylpropanoids (elemicin is the major). Sylvestrene has never been reported before in the essential oil of any Daucus species. The study of the essential oil of the leaves revealed the presence of monoterpene hydrocarbons; limonene and gamma-terpinene are the majors and a small amount of sylvestrene. The essential oil of stems consists of monoterpene hydrocarbons (gamma-terpinene is the major), terpene alcohols (mainly 4-terpineol) and phenylpropanoids (myristicin and elemicin are the majors). It is interesting that, the essential oil of the fruits is free from any oxygenated terpenes while that of the stems is free from limonene and sylvestrene which are present in the essential oil of the fruits and leaves in fairly large amounts The essential oil of the fruits, leaves and stems shows broad antimicrobial activities against both gram positive and gram negative bacteria. In addition, the volatile oil of the stem, particularly, show activities against Candida albicans (yeast). Also, the prepared oils have variable cytotoxic activities with LC50 21.52, 36.01 and 42.34 microg/ml, respectively.

Taxonomic review on the African Umbelliferous genus Agrocharis: Inferences based on molecular data

The taxonomic position of umbel genus Agrocharis, endemic to tropical Africa, was reviewed on the basis of molecular phylogenies derived from sequences of nuclear ribosomal DNA internal transcribed spacer (ITS) regions. The ITS sequence-derived phylogeny indicates that Agrocharis is monophyletic and is closely related to a clade comprising Daucus species: African (D. bicolor and D. durieua), Australian (D. glochidiatus), and American (D. pusillus and D. montanus). This phylogeny provides evidence that characters based upon the fruit's secondary spines show a high degree of variation within the genus Agrocharis, and thus these characters are only of limited value for delimiting the species boundary within the genus. The larger and more variable shapes of the secondary spines are considered to have evolved independently in these spiny-fruited umbel plants as an adaptation to locally changing environmental conditions for fruit dispersal.

Somatic embryogenesis and DNA organization of genomes from selected Daucus species

Under identical culture conditions, only 8 out of 12 species and subspecies of the genus Daucus proved capable of somatic embryogenesis. Random amplified polymorphic DNA analysis indicated a polymorphism between the genomes of individual species that were capable of embryogenesis and those that were not. Two specific bands (1.1 kbp, 0.68 kbp) were detected only in the genomes of individuals with the capacity for embryogenesis. These were cloned and sequenced, and the homology of the nucleotide sequences of the various species was detected: this ranged from 74% to 92% for the larger sequence and from 92% to 97% for the smaller one. These DNA sequences would appear to be useful as a marker of the capacity for somatic embryogenesis in the genus Daucus.

Male sterility in populations of Daucus and the development of alloplasmic male‐sterile lines of carrot

AbstractA collection of Daucus species and subspecies, as well as alloplasmic carrot lines were evaluated for expression of male sterility. More than 100 male‐sterile plants were identified and their phenotypes and partial genetic background were characterized. Three potentially new cytoplasmic male‐sterile systems based on the cytoplasm of Daucus carota (D. c.) gummifer, D. c. maritimus and D. c. gadecaei were selected. Genetic analyses suggested that a nuclear‐cytoplasmic interaction determined the male sterility of the three sources. A clear differentiation between the new sources and carrot cultivars was possible based on the phenotypic and molecular genetic relationships.

Phylogeny and relationships in Daucus based on restriction fragment length polymorphisms (RFLPs) of the chloroplast and mitochondrial genomes

Chloroplast DNA (cpDNA) restriction site analysis of nine species of Daucus (covering four of five sections) and nine carrot accessions was done using 14 Petunia cpDNA clones as probes and 10 restriction enzymes. Cladistic analysis yielded a phylogeny generally concordant with a recent morphological classification. A cpDNA insertion-deletion mutation was found in the cultivated carrots (probe P10– Bgl II digest). Mitochondrial DNA (mtDNA) restriction site analysis of the same material using four maize mtDNA clones as probes and 10 enzymes exhibited extensive mitochondrial diversity in Daucus, both within and between sections.

The Identification and Exploitation of Resistance in Carrots and Wild Umbelliferae to the Carrot Fly, Psila rosae (F.)

Partial plant resistance to the carrot fly, Psila rosae, has been identified in several Nantes varieties of carrot, Daucus carota, which reduces larval damage to the roots and the number of pupae remaining in the soil after cropping by 50%. The resistance of the Nantes variety 'Sytan' was found to be consistent at 12 sites in 5 European countries over two seasons. The resistance has been shown to be based on antibiosis and correlated with concentrations of chlorogenic acid in the roots. The resistance complements cultural and chemical methods for controlling P. rosae. Thus, in field experiments over two seasons it was shown that carrots could be left in the ground for a longer period providing a greater sowing/harvesting interval with a resistant variety than a susceptible one because of the reduction in damage and the delayed development of insects on the resistant variety. In two seasons at two sites a partially-resistant variety required only one-third of the dose of insecticide to provide a marketable crop compared with a susceptible carrot variety. In a breeding programme involving the variety 'Sytan', male sterile lines, inbreds and selections with improved levels of resistance were developed. Much higher levels of resistance were identified in certain wild Daucus species and 15 years of crossing and selection produced lines with significantly higher levels of resistance than exists in the variety 'Sytan'. A range of resistant carrot material bred at Horticulture Research International has been released to seed companies for use in the production of improved carrot varieties. The partially-resistant variety 'Flyaway' was made available to amateur gardeners in 1993 and to commercial growers in 1995 as a result of this research.

Genetic Relationships and Diversity in Carrot and other Daucus Taxa Based on Nuclear Restriction Fragment Length Polymorphisms

Current classifications of the genus Daucus are based on morphological and anatomical characteristics. We have used single to low copy nuclear restriction fragment length polymorphisms (nRFLPs) to describe the phylogeny and relationships of eight Daucus species including cultivated carrot (D. carota L.). Parsimony analysis of 247 characters (DNA fragments from 58 probe-enzyme combinations) yielded a tree in which accessions were grouped into three major clades and phenetic analysis using Jaccard's coefficient yielded two major clusters. The phylogenetic relationships from the nuclear RFLP data generally agreed with an earlier morphological classification. Resolution and placement of D. guttatus and D. muricatus were not consistent with the morphological classifications. Molecular variation among carrot inbreds was large.

Characterization of genetic diversity of nuclear and mitochondrial genomes in Daucus varieties by RAPD and AFLP

The genetic diversity of nuclear genomes of five Daucus species and seven Daucus carota L. subspecies involving 26 accessions was characterized with random amplified polymorphic DNA (RAPD) and amplified fragment length polymorphism (AFLP). AFLP produced more than four times as many discrete bands per reaction compared with RAPD analysis, while both AFLP and RAPD basically led to similar conclusions. The dendrograms constructed with both RAPD and AFLP revealed that all accessions of D. carota were grouped into a major cluster delimited from other Daucus species, in good agreement with the classification by morphological char-acteristics. All accessions of cultivated carrots [(D. carota ssp. sativus (Hoffm.) Arcang.] were clustered in the same group while the variation within D. carota was relatively extensive. Genetic diversity of mitochondrial genomes was also documented with RAPD for the same accessions. The mitochondrial dendrogram differed from that of the nuclear genome, suggesting that nuclear and mitochondrial genomes of some accessions had separate evolutionary histories.

Exploitation of the resistance to carrot fly in the wild carrot species Daucus capillifolius

SummaryUnder field conditions a wild Daucus species from Libya, D. capillifolius, supported less than one tenth as many carrot flies (Psila rosae) as the susceptible carrot cultivar Danvers Half Long 126. Breeding lines developed from crosses between D. capillifolius and three different carrot types were grown in a series of field experiments at Wellesbourne between 1980 and 1989. Each year selections were made for agronomic quality and/or for increased resistance to carrot fly. The programme produced lines which for size, shape and colour represented most of the commercially‐important carrot types. Some of these lines were also significantly more resistant to carrot fly than selections from the partially‐resistant cv. Sytan. However, the best lines were not as resistant as the wild parent. The highest quality resistant lines were sold to seed companies for variety production.

Ultrastructural investigations of mature embryo sacs of Daaucus carota, D. aureus and D. muricatus ? possible cytological explanations of paternal plastid inheritance

The embryo sacs of Daucus carota, D. Aureus and D. muricatus are of the Polygonum-type. They contain one egg cell, two synergids, a giant central cell and three antipodal cells that are to a great extent degenerated. The species of Daucus investigated have an egg cell with a vacuole that is large in comparison to the amount of cytoplasm. The most extreme case of reduced cytoplasm with respect to the volume of the vacuole occurs in D. muricatus. The egg cell of this species contains only very few intact plastids and other cytoplasmic organelles. Paternal plastid inheritance in the cross D. muricatus × D. carota is discussed in connection with the small number of cytoplasmic organelles in the female gamete of D. muricatus.