The young stem has small clusters of adventitious roots emerging from the stem at nodes opposite to the leaves. Two of these are indicated by black arrows. On the older stem, adventitious roots emerge along the entire length, making it look hairy. There are a few particularly dense clusters, indicated by arrows. Above the netted root system, there is a short collar, then sheathing leaves emerge, indicating the transition to shoot tissue.
At the base of these leaves, several prop roots are emerging. Carrot is an allogamous plant. The stamens usually mature earlier than pistils in carrots 24 , The rate of natural hybrids in carrots is very high, but the value of seed production by natural hybrids is uncertain Male sterile lines have been used in the hybridization breeding of many crops and have made hybridization breeding easier for many plants that are difficult to breed using artificial emasculation In heterosis breeding, male sterile lines were also widely used.
F 1 -hybrid breeding based on cytoplasmic male sterility is the main method of carrot breeding Morelock has identified this type in many cultivated and wild carrots This type was found by Thompson 31 and Mccollum 32 in wild carrot. In , Tan et al. The male sterile carrot line has no swollen storage root, petal or anther. The advantage of the F 1 hybrid is obvious In their subsequent experiments, they found that the sequence length of ATP synthase subunit 6 atp6 was shorter in the male sterile line Wuye-D and longer in the fertile line Wuye-L.
The atp6 gene is related to the fertility of plants. They thought that the longer atp6 gene was associated with carrot fertility and that the short atp6 gene was associated with carrot male sterility In a study by Szklarczyk et al. In Sp-cytoplasm carrot, the enhanced expression level of atp was thought to be responsible for the enhanced ATP9 accumulation However, male sterility is a genocytoplasmic system, and the mutation in the atp6 gene sequence is not enough to determine plant male sterility.
More genetic evidence is needed to determine plant male sterility. They can be used in identifying core collections and examining the genetic relationship between parents in breeding research In genetic diversity analysis, molecular markers are also useful In basic research and breeding of carrots, molecular markers have been widely used. In a study by Briard and colleagues, random amplified polymorphic DNA RAPD was found to perform better than morphological or isoenzymatic markers in the varietal identification of carrot In the characterization of genetic diversity in Daucus varieties, 26 accessions of Daucus were discriminated into five Daucus species and seven D.
Lian et al. Six sequence-tagged site STS primer combinations were used to identify the carrot petaloid type of cytoplasmic male sterility CMS. Five CMS lines were classified into two groups, and eight fertile carrots were classified into six groups In breeding carrots for resistance to leaf blight, quantitative trait locus QTL mapping technology was used to identify QTLs in carrots with new genetic backgrounds.
Eleven QTLs were found in the two carrots with new genetic backgrounds of resistance to Alternaria dauci Among the molecular markers, simple sequence repeat SSR markers are an important way to analyze genetic diversity. In the research of Baranski et al. Thirty SSR loci were fully characterized in these carrot accessions. As a result, the genetic diversity of the Western gene pool was lower than that of the Asian gene pool In these studies, many molecular markers have been identified.
Among these markers, some are disease resistance-related, some are agricultural trait-related and some reflect genetic diversity. All these markers will play important roles in carrot breeding with the carrot genome sequence database. Carrot is known as one of the pioneer species in the research of plant tissue culture The transformation protocols of carrots have also been established over decades.
Many transformation methods for carrots have been established. Among the diverse techniques, Agrobacterium -based systems are the most common methods 48 , Agrobacterium includes A.
The first carrot transformation based on A. According to many optimized transformation protocols of carrot transgenesis systems, explant type, variety, and bacterial strain were found to be the main factors affecting the transformation frequency 48 , In carrots, roots, cotyledons, hypocotyls, and petioles can all be used as explants. The time of cocultivation was also important. Compared with a cocultivation time of 1 or 7 days, the transformation frequency at a cocultivation time of 2 or 3 days was higher In the breeding research on carrots, the genetic engineering method was also adopted.
The approach based on overexpressing functional genes was widely used. In the research of Wally et al. The transgenic lines overexpressing OsPrx displayed high disease resistance compared with the control In addition to resistance breeding, genetic engineering was also used to accumulate some special components by overexpressing characteristic genes in carrots. In the research of Luchakivskaya et al.
This genome editing system has been applied in many spaces, including humans, mice, and plants 56 , 57 , In , this genome editing system was first employed in carrot research. Klimek-Chodacka et al. Xu et al. The transformation method of carrots has matured. Transgenic breeding of carrots has been widely applied in experimental studies, and many important functional genes have been determined by overexpression or genome editing.
However, this method should be used cautiously in field production. Aster yellows is an insect-vectored carrot disease caused by a mycoplasma-like organism. This disease is one of the important diseases that limits the growth and yield of carrot 61 , Carrots infected by this typical disease will show stunting, yellowing, leaf bronzing, sterility and leaf-like petals Breeding carrot disease resistance to aster yellows has been implemented for many years.
Gabelman and his collaborators selected breeding lines with high resistance to aster yellows through field evaluation and selection. Fungal leaf blight is a kind of foliar disease in the cultivation of carrots.
Fungal leaf blights are mainly caused by A. Solheim around the world Fungal leaf blights are found to cause yield loss by reducing leaf photosynthetic area and breaking carrot petioles. The A. Breeding for leaf blight resistance has been performed for many years. The less-susceptible cultivars are found to have characteristics that delay the spread rate of pathogens. In the research of Le Clerc et al. The carrot fly, Psila rosae F.
Diptera: Psilidae , is the most serious and widespread pest in carrot production Carrot leaves turn red, orange or rust- colored, and roots present rusty brown scars and tunnels when infected by carrot flies. Carrots infected by carrot flies are inedible and unmarketable Reports about carrot fly resistance breeding are available from more than years ago From to , Ellis and his group performed carrot fly resistance breeding at 12 different locations in England.
The results of the comparative experiment suggested that carrots with high resistance to carrot flies reduce fly damage by delaying the development of larvae To overcome the effect of environmental factors in variety selection, Ellis and his group developed inbred carrots by using a single seed descent program. A total of nine carrot lines with moderate resistance to carrot fly were selected and seeded During breeding progress, it was realized that varieties with high carrot fly resistance have lower levels of chlorogenic acid than varieties with low resistance The concentration of chlorogenic acid may be used as a selection criterion to select a variety with high resistance to carrot flies.
However, reports about genetic research into the resistance to carrot flies in carrots are still scarce. Root-knot nematodes RKNs are significant pests that are widely present in plants In many carrot-producing regions, RKNs are major pests that limit carrot production In cooler producing regions, Meloidogyne hapla is the most prevalent. In warmer producing areas, Meloidogyne javanica and Meloidogyne incognita are the predominant RKN species The characteristics of RKNs present in soil and having a broad host range and the limited use of nematicides lead to difficulty in controlling the pathogen To guarantee carrot quality, it is necessary to perform root-knot nematode resistance breeding in carrots.
Huang et al. In , another locus that imparts resistance to M. The discovery of Mj-1 and Mj-2 is meaningful for the root-knot nematode resistance breeding of carrots. Over the past few decades, sequencing technology has developed rapidly, and more than plant genomes have been sequenced 7. As the most important vegetable in the Apiaceae family, the carrot genome was also sequenced. In , a genomic database for the carrot was released. This database provides de novo assembled whole-genome sequences and classified transcription factor families of carrots, which is helpful for further research on carrots Two years later, a high-quality carrot genome In this study, the evolution of the carrot genome was analyzed, and two new whole-genome duplications WGDs were identified.
Based on the whole-genome sequencing of carrots, 32, genes were predicted. Among the 32, genes, 10, genes unique to carrots were found All of these genome sequence data will significantly promote research on carrot evolution, carotenoid synthesis, and many other important projects in carrots. In future research, the two carrot genome datasets should be combined in carrot studies. The plastid genome of carrots has also been sequenced. In , the plastid genome of carrot was sequenced by Ruhlman et al.
The results from that research provided a valuable resource for phylogenetic analysis among different angiosperms. The results strongly supported the sister relationship between Daucus and Panax Transcriptomics is an approach to studying gene expression by measuring all mRNA transcripts in one cell or tissue. The transcriptome sequence dataset is widely used in analyzing gene expression, discovering gene functions, and developing molecular markers 91 , In carrot research, transcriptomics was also widely adopted.
To our knowledge, this transcriptome is the first transcriptome of carrot. In addition, polymorphisms were found predominantly between inbred lines The database was established based on transcriptomic sequences from 14 carrot genotypes To further investigate the domestication of carrots, the root transcriptomes of six cultivated carrots and five wild carrots were sequenced.
Rong et al. In cultivated carrots, the expression of the water-channel-protein gene and carotenoid-binding-protein gene was upregulated, and the expression of allergen-protein-like genes was silenced 3. All these results revealed the potential role of regulators of gene expression in domestication.
The western carrots were thought to originate from eastern carrots based on the analysis of transcriptome data from different cultivated and wild carrots. Phytohormones play important roles in controlling plant root growth and development. As a root vegetable, the effect of hormones on carrot root growth should be investigated.
To investigate the molecular mechanisms of hormones on carrot root growth, the transcriptomes of four different developmental stages were sequenced. A total of unigenes with differential expression between the four stages were identified. Among the unigenes, 87 genes were found to be involved in the hormone-related pathway The transcriptome analysis of the key genes involved in the biosynthesis and signaling pathway of phytohormones helped to clarify the roles of hormones during root development.
To investigate the biosynthesis of carotenoids in carrot leaves and roots, Ma et al. Based on the transcriptome data, DcPSY1 was thought to be the crucial factor responsible for the higher carotenoid content in carrot leaves.
Depending on the demands of different studies, various transcriptome sequence datasets have been generated. All the datasets are the sequences of genes that are expressed under certain conditions.
Transcriptomics promotes research on carrots, and many single important genes were found through this method. On the other hand, research on the relationship among different genes is also interesting. In the future, more research on the interaction among genes based on transcriptome sequence datasets should be performed in carrots. Numerous studies have found that plant miRNAs preferentially target transcription factors and play important roles in regulating plant development As a consensus, miRNA may be an important research object in research on improving the agronomic characteristics of crops.
The first carrot microRNA database was reported in Seventeen microRNAs were identified from the research. The 17 microRNAs came from 12 different families dca-mir, , , , , , , , , , and In analyzing the potential targets of the 17 microRNAs, 24 targets were determined.
Among the 24 potential targets, 8 were transcription factors, 6 were stress related, 5 were involved in metabolism and 4 were related to plant growth. Most targets identified in the research have also been reported as microRNA targets in other plants The microRNA database and the findings are valuable resources for further research in improving the agronomic characteristics of carrots. Unfortunately, research about the microRNA in carrots is still scarce. Proteomics is an important technology for studying the growth, development, and stress responses of plants by systematically analyzing the plant proteome.
This technology is an important complement to the genome , Through proteomics, numerous proteins involved in the complex signaling and metabolic network of plants can be qualitatively and quantitatively analyzed In stress-response research in plants, proteomics has proven to be a powerful method and has been used in studying drought, flooding, and nutritional stress responses Furthermore, proteomics has also been widely used in studying the mechanisms and biological processes of plants, such as fruit ripening, seed germination, and floral development In the research of Louarn et al.
Carrots cultivated in two different cropping systems were selected as the research object. A total of 15 proteins were found to change in levels in the first month of storage. Between the two different cropping systems, the change in protein level was small.
Among the 15 proteins, three were related to the stress response, and three were related to the cytoskeleton. The research indicated that carrot roots have an adaptation to the low temperature within the first month of cold storage In the research of Wang et al. Through proteome sequencing, they found a potential molecular mechanism for the altered lignin content in carrot roots induced by elevated CO 2 Proteomic technology provides a powerful way to understand the complex signaling and metabolic network of plant physiological progress and can contribute to further investigation of improving carrot yield and nutrition.
The cell or the tissue measured is always in a particular physiological or developmental state This is a novel approach to performing qualitative and quantitative studies on plant biochemistry at a global level. Metabolomics has been widely adopted to study plant metabolism and food quality To investigate the difference between wild and cultivated carrots, Grebenstein et al.
Differences between the two kinds of carrots only appeared at the quantitative level in the metabolic content. The metabolome of the hybrid of wild and cultivated carrots showed high similarity to that of the maternal carrot. The maternal characteristics and maternal environment may be the factors leading to the similar metabolic content between hybrid and maternal carrots In carrot breeding research, metabolomics is also used as a powerful tool. A cultivated carrot Ingot was found to have the highest resistance.
The wild and biofortified carrots did not show distinct resistance to the thrips. The contents of the flavanoid luteolin, the phenylpropanoid sinapic acid and the amino acid balanine were more abundant in the resistant carrots. These results were useful in the research of thrip resistance breeding in carrots In , the metabolomes of five carrot varieties were measured by NMR to study the effect of genotype on the metabolite components of carrot.
The difference between yellow and white carrot varieties was unclear. Genetic differences, growing strategies, and soil types were finally determined to be the factors that affect the composition of different carrot varieties. The results are useful in breeding to improve carrot quality Phytohormones are important regulators of plant growth and environmental responses. They are involved in almost all physiological processes during the growth and development of plants, such as cell division, growth and differentiation, flowering, seed development, and senescence , Auxin is a pivotal plant hormone whose cellular level is important for regulating plant growth and development.
Fruit formation, leaf abscission, cell division, and cell elongation were all reported to be regulated by auxin , Among the different kinds of naturally active auxins, IAA is the best studied In the research of Wu et al. In addition, 18 genes involved in the biosynthesis and signaling pathway of IAA were identified. The way that IAA regulates carrot growth and development may be tissue-specific However, there are few reports on the effect of exogenous IAA on the field production of carrots.
Gibberellins are diterpenoid compounds. Through the whole life cycle of plants, GAs play pivotal roles in regulating growth and development, including seed germination, stem elongation, flowering, and fruit development In cellular growth, promoting the elongation and expansion of cells are the main functions of GAs. Mutants that are defective in GA biosynthesis are always dwarfs During the growth and development of carrots, GAs play pivotal roles.
In carrots, the content levels in roots are lower than those in petioles and leaf blades Through foliar application, exogenous GA 3 promotes the growth of the aboveground part and inhibits the growth of roots At higher temperatures, GA spray application can influence carrot flowering The impact of GAs on carrot roots promotes the development of secondary xylem and decreases the proportion of secondary phloem In a study by Wang et al.
In addition, GA was involved in the regulation of the differentiation of embryogenic cells in carrot Brassinosteroids BRs are steroid hormones, an important kind of plant regulator To date, more than 70 brassinosteroid compounds have been isolated, and brassinolide is the most bioactive compound During plant growth and development, BRs are involved in various biological processes, such as the formation of stomata and lateral roots, flowering, and fruit maturation.
BRs also play important roles in promoting cell division, vascular differentiation and cell elongation, and enhancing the tolerance of the plant , The spatiotemporal distribution of brassinosteroid activity is a decisive factor that influences the function of BRs However, the precise spatial and subcellular distribution of BRs in plant organs is still unclear.
Regarding the biosynthesis and signal transduction of BRs, the related genes have been determined by using BR-related mutants in Arabidopsis and many other plants In carrots, genes involved in the biosynthesis and signal transduction pathways have been identified via transcriptomic research.
Foliar application of epibrassinolide was proven to promote the elongation of carrot petioles. The aboveground part of the carrot treated with epibrassinolide was taller and heavier than that without treatment Abscisic acid ABA was first recognized as a plant hormone in the early s ABA plays important roles in regulating almost all physiological processes during plant growth and development, including seed dormancy, seed germination, and fruit maturity In the presence of environmental stress, ABA plays important roles in inducing stomatal closure to respond to water deficiency In carrots, most reports about ABA are related to somatic embryogenesis.
Kiyosue et al. They found that embryogenic cells had the highest level of ABA In the research of Nishiwaki et al. In addition, ABA plays an important role in inducing the secondary embryogenesis of carrot somatic embryos In Arabidopsis , salt stress was found to induce carotenoid synthesis to contribute to ABA production These results suggest a critical relationship between carotenoids and ABA.
Now that you know the answer to the question, does carrot have a tap root or a fibrous root, keep reading to find out more about carrots. The carrot Daucus carota sativa is a biennial crop planted from nursery-grown seedlings or sown directly in the garden. The plant requires loose soil, cool weather, and plenty of water to grow.
Taproots are a primary root system in dicotyledonous plants. In this root system, a central primary dominant root forms from the radicle and grows downwards. Other secondary smaller roots grow on the taproot, and further tertiary roots grow from the secondary roots. This root system does well in loose and well-drained soils. Taproots can stretch very deep to extremes of 75 feet in some desert plants and thus are able to reach water even in times of drought.
Taproots anchor the plant into the soil exceptionally well, ensuring the plant is stable and difficult to uproot. In most cases, plants store products of photosynthesis in the form of starch and nutrients in taproots for use in droughts and when flowering as well as during seed production.
Major types of taproots include:. Many factors affect the shape and size of carrots and these include carrot genetics, soil type, soil preparation, plant spacing, temperatures, and the availability of nutrients. Mainly, taproot length and width depend on the soil type and preparation.
All factors held constant, carrots grown in loose, well drained, and highly nutritious soils are broader and more prolonged. Also, plant spacing and density determine the room available for enlargement, and consequently, the root size. Branching in carrots is mainly hereditary but can also occur due to under composted organic matter. Furthermore, injury to the root cap from growing into an obstacle or by insects may also result in branching.
The roots become slender and long when grown in temperatures between 13 and 20 0 C. However, the harvest length and shape of the carrot principally form during the early phases of the plant development. They lay eggs in the soil that hatch to larvae, which survive on carrot roots. Consequently, they lower the quality of the crop.
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