Morphological and molecular changes on cytoplasmic male sterility (CMS) introgression in Asiatic carrot (Daucus carota L.).

MAIN CONCLUSION: 'Petaloid' cytoplasmic male sterility is commonly used as a stable genetic mechanism in carrot hybrid breeding. Its introgression in tropical carrot showed morphometric changes and molecular markers were identified for detection at early stage. Cytoplasmic male sterility (CMS) is the only genetic mechanism in carrot for commercial exploitation of heterosis and production of low cost affordable hybrid seeds. The 'petaloid' CMS system is stable and commonly used in hybrid breeding in temperate carrot but there is no information available on existence of natural CMS system in tropical Asiatic carrot. Therefore, the present study was aimed to investigate morphometric traits and organizational features of cytoplasmic atp9 gene sequences in newly converted CMS lines (BC4-7) of tropical carrot. The CMS lines had root traits at par with fertile counterparts while floral traits had variation. Petal colour and length, petaloids colour and shape and style length showed differences among the CMS lines and with their maintainers. Molecular markers are effective to establish male sterility at genetic level, for this, six fixed and stable CMS lines were screened with seven novel primer combinations. Out of which five pairs produced clearly distinguishable bands in CMS lines and their fertile counterparts. The study confirmed that the region between 3' end of atp9-1/atp9-3 gene and 5' end of region of homology to Arabidopsis thaliana mtDNA is ideal for developing the trait specific markers. These new CMS lines have potential to use in hybrid development and molecular markers will be useful to confirm male sterility to rogue out fertile plants.

Hypoxia enhances lignification and affects the anatomical structure in hydroponic cultivation of carrot taproot.

KEY MESSAGE: Hypoxia enhances lignification of carrot root. Hypoxia stress was thought to be one of the major abiotic stresses that inhibiting the growth and development of higher plants. The genes encoding the plant alcohol dehydrogenase (ADH-P) were induced when suffering hypoxia. To investigate the impact of hypoxia on the carrot root growth, carrot plants were cultivated in the hydroponics with or without aeration. Morphological characteristics, anatomical structure, lignin content, and the expression profiles of DcADH-P genes and lignin biosynthesis-related genes were measured. Six DcADH-P genes were identified from the carrot genome. The expression profiles of only three (DcADH-P1, DcADH-P2, and DcADH-P3) genes could be detected and the other three (DcADH-P4, DcADH-P5, and DcADH-P6) could not be detected when carrot cultivated in the solution without aeration. In addition, carrot roots had more lignin content, aerenchyma and less fresh weight when cultivated in the solution without aeration. These results suggested that hypoxia could enhance the lignification and affect anatomical structure of the carrot root. However, the expression levels of the genes related to lignin biosynthesis were down-regulated under the hypoxia. The enhancement of lignification may be the consequence of the structure changes in the carrot root. Our work was potentially helpful for studying the effect of hypoxia on carrot growth and may provide useful information for carrot hydroponics.

Genotyping-by-sequencing provides the discriminating power to investigate the subspecies of Daucus carota (Apiaceae).

BACKGROUND: The majority of the subspecies of Daucus carota have not yet been discriminated clearly by various molecular or morphological methods and hence their phylogeny and classification remains unresolved. Recent studies using 94 nuclear orthologs and morphological characters, and studies employing other molecular approaches were unable to distinguish clearly many of the subspecies. Fertile intercrosses among traditionally recognized subspecies are well documented. We here explore the utility of single nucleotide polymorphisms (SNPs) generated by genotyping-by-sequencing (GBS) to serve as an effective molecular method to discriminate the subspecies of the D. carota complex. RESULTS: We used GBS to obtain SNPs covering all nine Daucus carota chromosomes from 162 accessions of Daucus and two related genera. To study Daucus phylogeny, we scored a total of 10,814 or 38,920 SNPs with a maximum of 10 or 30 % missing data, respectively. To investigate the subspecies of D. carota, we employed two data sets including 150 accessions: (i) rate of missing data 10 % with a total of 18,565 SNPs, and (ii) rate of missing data 30 %, totaling 43,713 SNPs. Consistent with prior results, the topology of both data sets separated species with 2n = 18 chromosome from all other species. Our results place all cultivated carrots (D. carota subsp. sativus) in a single clade. The wild members of D. carota from central Asia were on a clade with eastern members of subsp. sativus. The other subspecies of D. carota were in four clades associated with geographic groups: (1) the Balkan Peninsula and the Middle East, (2) North America and Europe, (3) North Africa exclusive of Morocco, and (4) the Iberian Peninsula and Morocco. Daucus carota subsp. maximus was discriminated, but neither it, nor subsp. gummifer (defined in a broad sense) are monophyletic. CONCLUSIONS: Our study suggests that (1) the morphotypes identified as D. carota subspecies gummifer (as currently broadly circumscribed), all confined to areas near the Atlantic Ocean and the western Mediterranean Sea, have separate origins from sympatric members of other subspecies of D. carota, (2) D. carota subsp. maximus, on two clades with some accessions of subsp. carota, can be distinguished from each other but only with poor morphological support, (3) D. carota subsp. capillifolius, well distinguished morphologically, is an apospecies relative to North African populations of D. carota subsp. carota, (4) the eastern cultivated carrots have origins closer to wild carrots from central Asia than to western cultivated carrots, and (5) large SNP data sets are suitable for species-level phylogenetic studies in Daucus.

Exogenous gibberellin altered morphology, anatomic and transcriptional regulatory networks of hormones in carrot root and shoot.

BACKGROUND: Gibberellins stimulate cell elongation and expansion during plant growth and development. Carrot is a root plant with great value and undergoes obvious alteration in organ size over the period of plant growth. However, the roles of gibberellins in carrot remain unclear. RESULTS: To investigate the effects of gibberelliins on the growth of carrot, we treated carrot plants with gibberellic acid 3 (GA3) or paclobutrazol (a gibberellin inhibitor). The results found that GA3 dramatically reduced the root growth but stimulated the shoot growth of carrot. It also significantly promoted xylem development in the tuberous root of carrot. In addition, transcript levels of genes related to gibberellins, auxin, cytokinins, abscisic acid and brassinolides were altered in response to increased or reduced gibberellins. CONCLUSIONS: The inhibited tuberous root growth but enhanced shoot growth in plants treated with GA3 can be principally attributed to the changes in the xylem development of carrot roots. Negative feedback regulation mechanism of gibberellin biosynthesis also occurred in response to altered gibberellin accumulation. Gibberellins may interact with other hormones to regulate carrot plant growth through crosstalk mechanisms. This study provided novel insights into the functions of gibberellins in the growth and development of carrot.

Carotenoid content and root color of cultivated carrot: a candidate-gene association study using an original broad unstructured population.

Accumulated in large amounts in carrot, carotenoids are an important product quality attribute and therefore a major breeding trait. However, the knowledge of carotenoid accumulation genetic control in this root vegetable is still limited. In order to identify the genetic variants linked to this character, we performed an association mapping study with a candidate gene approach. We developed an original unstructured population with a broad genetic basis to avoid the pitfall of false positive detection due to population stratification. We genotyped 109 SNPs located in 17 candidate genes ­ mostly carotenoid biosynthesis genes ­ on 380 individuals, and tested the association with carotenoid contents and color components. Total carotenoids and ß-carotene contents were significantly associated with genes zeaxanthin epoxydase (ZEP), phytoene desaturase (PDS) and carotenoid isomerase (CRTISO) while α-carotene was associated with CRTISO and plastid terminal oxidase (PTOX) genes. Color components were associated most significantly with ZEP. Our results suggest the involvement of the couple PDS/PTOX and ZEP in carotenoid accumulation, as the result of the metabolic and catabolic activities respectively. This study brings new insights in the understanding of the carotenoid pathway in non-photosynthetic organs.

Effects of genotype, soil type, year and fertilisation on sensory and morphological attributes of carrots (Daucus carota L.).

BACKGROUND: The aim of the study was to investigate the effects of variety, soil type and fertilisation, and the interactions between these factors, on yield and quality traits of carrots. RESULTS: Optimum fertilisation levels for yield and quality of grade one roots were found to be between 80 and 160 kg ha(-1) for nitrogen and between 0 and 120 kg ha(-1) for potassium depending on soil type and precipitation. Carrots grown in peat soil had the highest score for sweetness and the lowest scores for negatively associated characteristics such as bitterness, earthy flavour, terpene flavour and firmness. Nitrate content and the amounts of splitted and forked roots were lowest on sandy soil. Variety significantly affected number of grade 1 roots, dry matter, nitrate content and most of the sensory attributes tested. Interactions between variety, soil type and nitrogen fertilisation were found for most of the tested quality characteristics. CONCLUSION: The investigations showed that year and variety had the highest impact on the carrot quality attributes studied, whereas soil type and fertilisation had less influence. Peat soil and moderate fertilisation with N and K gave optimal sensory quality while sand soil gave optimal quality as regards morphological characters like splitting and forking of roots as well as nitrate content.

Suboptimal temperature favors reserve formation in biennial carrot (Daucus carota) plants.

In response to suboptimal temperatures, temperate annual plants often increase root:shoot ratios, build-up carbohydrates and display typical morphological and anatomical changes. We know less about the responses of biennials such as carrot. As a model plant, carrot has the additional feature of two functionally and morphologically distinct root parts: the taproot, which stores carbohydrate and other compounds, and the fibrous root system involved in acquisition of water and nutrients. Here, we analyze the effects of temperature (12 vs 25°C) on growth, carbohydrate accumulation and whole-plant morphology in two carrot cultivars. Our working hypothesis is that suboptimal temperature favors active formation of reserve structures, rather than passive accumulation of storage carbohydrates. In comparison with plants grown at 25°C, plants grown at 12°C had: (1) higher fibrous root:shoot ratio (13%) , (2) thicker (10-15%) and smaller (up to two- to three-fold) leaves, (3) lower leaf cuticular permeance (two- to four-fold), (4) higher taproot:shoot ratio (two-fold), (5) higher phloem:xylem ratios in taproot (two- to six-fold), (6) unchanged percentage dry matter content (%DMC) in leaves, petioles or fibrous roots and (7) higher %DMC in taproot (20%). However, %DMC of individual taproot tissues (phloem and xylem) was unaffected by temperatures and was consistently higher in the phloem (up to 30%). Therefore, the higher %DMC of whole taproots at 12°C was attributed solely to the increased development of phloem tissue. Carrot, therefore, shares many of the most conspicuous elements of temperate plant responses to low temperatures. Consistently with our hypothesis, however, carrots grown at suboptimal temperature promoted reserve structures, rather than the increase in carbohydrate concentration typical of most temperate annual species and woody perennials.

Genetic architecture of factors underlying partial resistance to Alternaria leaf blight in carrot.

In most production areas, Alternaria leaf blight (ALB) is recognized as the most common and destructive foliage disease in carrot. To assess the genetic architecture of carrot ALB resistance, two parental coupling maps were developed with similar number of dominant markers (around 70), sizes (around 650 cM), densities (around 9.5 cM), and marker composition. The F(2:3) progenies were evaluated in field and tunnel for two scoring dates. The continuous distribution of the disease severity value indicated that ALB resistance is under polygenic control. Three QTLs regions were found on three linkage groups. Two of them were tunnel or field specific and were detected only at the second screening date suggesting that the expression of these two QTLs regions involved in resistance to Alternaria dauci might depend on environment and delay after infection.

Nutritional, physical, and sensory evaluation of hydroponic carrots (Daucus carota L.) from different nutrient delivery systems.

Carrot (Daucus carota L.) has the highest carotenoid content among foods and is consumed in large quantities worldwide, while at the same time its market demand continues to increase. Carotenoids have also been associated with protective effects against cancer and other chronic diseases. The most predominant carotenoids in carrots are beta- and alpha-carotenes. Moisture, ash, fat, texture, color, carotene content, and consumer acceptance of carrots grown in a hydroponic system with nutrient film technique (NFT) and microporous tube membrane system (MTMS) were evaluated. The moisture contents of the NFT- and MTMS-grown carrots ranged from 86.8 +/- 0.13% to 92.2 +/- 2.25% and 80.9 +/- 0.31% to 91.6 +/- 1.01%, respectively. Fat and ash contents of the carrots were negligible. NFT-grown Oxheart had the most beta-carotene (9900 +/- 20 microg/100 g) while Juwaroot had the least (248 +/- 10 microg/100 g). However, the beta-carotene content of Juwaroot from the NFT batch II carrots was 3842 +/- 6 microg/100 g. MTMS-grown carrots had less variation in the total beta-carotene contents (2434 +/- 89 to 10488 +/- 8 microg/100 g) than those from NFT. Overall, Nantes Touchan (4.8 +/- 2.3) and Nevis-F (7 +/- 1.4) from NFT were the least and most preferred by consumers. Mignon was also acceptable to consumers, and significantly (P < 0.05) more preferred than the other carrots in that NFT batch. MTMS-grown Kinko and Paramex, which were significantly (P < 0.05) more preferred than Nandrin-F and the commercial field-grown carrot, were equally liked by consumers. Nevis-F, Mignon (NFT), Paramex, and Kinko (MTMS) are potentially good cultivars to be included in NASA's food system.

The effects of the fibre content and physical structure of carrots on satiety and subsequent intakes when eaten as part of a mixed meal.

Previous research indicates that vegetables yield relatively high satiety scores, and that fibre content and structure may both contribute to these effects. This study evaluated the effects of the fibre content and physical structure (gross anatomy and cell structure) of carrots on postprandial satiety and subsequent food intakes when consumed as part of a mixed meal. Using a randomised, repeated-measures, within-subject cross-over design, young women consumed a standardised breakfast and test lunches on three occasions, 4 weeks apart. The test lunches (3329 kJ) comprised boiled rice (200 g) with sweet and sour sauce (200 g) that included chicken (200 g) and carrots (200 g) in three conditions: whole carrots (fibre and structure; n 34), blended carrots (fibre but no structure; n 34) or carrot nutrients (no fibre or structure; n 32). The carrot nutrients had the same energy, major nutrients and portion weight as the other two conditions. Post-lunch satiety was assessed by visual analogue scales. Intakes were covertly weighed at a meal eaten ad libitum (3 h later), and for the remainder of the day using food diaries. Compared with the meal with carrot nutrients, meals with whole carrots and blended carrots resulted in significantly (P<0.05) higher satiety. There were significant (P<0.05) differences between conditions in intakes at the meal eaten ad libitum and for the remainder of the day, and intakes consistently decreased in the order: carrot nutrients, blended carrots, whole carrots, indicating that both fibre content and structure played a role in these effects.

Case report of a smuggler's dinner: carrots and asparagus, or bolitas?

BACKGROUND: Body packing is a distinct method of drug smuggling. Surgeons and intensive care specialists will be confronted with body packers when packets do not pass spontaneously and rupture, causing drug toxicity. CASE REPORT: We report of a 32-year-old Liberian male who presented with abdominal complaints and anxiety after having ingested 50 cocaine-containing packets of which 49 had passed the natural route in the previous days. X-ray of his abdomen showed a structure possibly compatible with a packet in or projected over the stomach. We decided to transfer the patient to the operation theatre for surgical removal via gastrotomy. However, no packet was found. During his first day in the intensive care unit he did not regain consciousness. Repeated urine analyses for cocaine were negative. After one day he deteriorated: he needed circulatory support because of hypotension, without signs of sepsis. Repeated surgery revealed no packet. In the end he turned out not to be suffering from cocaine intoxication. CONCLUSIONS: When confronted with a case of body packing in which packets do not pass spontaneously and produce bowel obstruction or in which badly wrapped packets rupture, causing drug toxicity, it is of utmost importance to establish the nature of the packet's content.

Regulation of an embryogenic carrot gene (DC 2.15) and identification of its active promoter sites.

According to previous studies the expression of the gene DC 2.15 is induced in cultured carrot cells after a transfer to an auxin-free medium, where somatic embryo development occurs. This embryogenic gene encodes a prolinerich protein, which resembles proteins involved in auxin-controlled developmental processes. To understand the mechanism underlying the regulation of DC 2.15, an experimental approach has been employed which allows the direct identification of the DC 2.15 promoter structure by applying PCR techniques. We demonstrate the presence of five distinct promoter sequences highly similar in structure, but slightly different in a common region of about 15 nucleotides, which contain the binding site for the GATA factor originally found in the human HOX gene. Activity of each promoter structure was assessed in developing somatic embryos containing the specific sequence fused to the beta-glucuronidase (GUS) reporter gene. For two of the five promoter structures a drastic increase in activity was registered during the torpedo stage while the remaining three were inactive throughout the stages of somatic embryogenesis.