Advances and Milestones of Radish Breeding: An Update

Radish is an annual herbaceous root crop, fruit, and oil crop plant belonging to the Cruciferae family. The important traits for radish breeding include high yield, early maturity, late bolting, pungency, cold-hardiness, drought resistance, heat tolerance, and soil adaptability. For successful radish production, need to the understand nature and behaviour of the flower, and very important to identify the S haplotypes of parental lines to produce F1 hybrids based on self-incompatibility to get rid of laborious hand emasculation in radish. In radish some desirable genes are not present within varieties. Therefore, further breeding programmes depend on inter-specific and intra-specific hybridization, which has a vital role in genomic studies and crop improvement by introducing desirable agronomic characters. It is essential to acquire detailed genetic information on chromosomes and information on inheritance. Genomics is now at the core of crop improvement, and radish crop is exploited to study the underlying differences in genotypes. But some monogenic characters are improved by genetic engineering. A three-decade span following the first documented instance of genetic engineering has witnessed its application's unprecedented growth. Researchers have successfully produced transgenic radishes with various agronomic characteristics over the last decade.


Introduction
Radish is an annual herbaceous vegetable known as Raphanus sativus (Jansen, 2021), and it is a diploid containing two sets of eighteen chromosomes (2n=18) (Richharia 1937). Radish belongs to the Cruciferae family, and it is eaten fresh as grated radish, a garnish, and a salad (Kaneko and Matsuzawa 1993). Radish is regularly served in eastern Asian cuisine; moreover, radish has also featured in food worldwide (Patra et al. 2016). There is a focus on developing high-quality radish varieties ideal for tropical and subtropical temperatures (Ebert 2013).
Additionally, breeding work has been performed on numerous agronomical traits include tolerance to pathogens, and consumption adaptability. Importance traits for radish breeding include high yield, early maturity, late bolting, pungency, cold-hardiness, drought resistance, heat tolerance, and soil adaptability (Kaneko and Matsuzawa 1993). There is a correlation between the radish's consistency and its amount of sugar, pungency, elaboration of the cell, water content, and pore extent . Now days, Mass selection or pedigree methods is utilized for developing on the focus on the red globe, oval red and white forms of radish (Kaneko et al. 2007). . Although, the main endeavor has been to modify the radish cultivation to various growing seasons (Simard and Légère 2004).. It is essential to acquire detailed genetic information on chromosomes and information on inheritance for various genes responsible for agronomical, biochemical traits and resistance to biotic and abiotic stresses for carrying out a successful radish breeding (Kumar 2012;Dixon 2007). The studies that need to use new approaches, including chromosome or gene alteration, need to be performed (Porteus and Carroll 2005).
Marketing assessment and consumer preference are primarily associated with physical attractiveness like length, shape, size, and skin colour (Petropoulos et al. 2019). A primary color changes into white and different pink, red, purple, yellow, and green, but the skin is usually white. In contrast, red color radishes have a mild flavor (not as pungent) and are around 40 cm in length . The anthocyanin pelargonidin is the color causing pigment in red colours, while in purple cultivars, the cyanidin derivative is responsible for the color. Although quality-related traits may be remarkably heritable, they are often strongly influenced by cultivation methods. The swollen tap roots of radishes may be oval, tapered, or cylindrical in terms of form (Rubatzky and Yamaguchi 1997). Moreover, mechanical harvesting often includes cylindrical root cultivars . Rich in antler velvet, radish roots produce useful phytochemicals, they have cancer-preventive properties and working as a significant contributor to the taste and flavor of the Brassica vegetables (Cartea et al. 2008). In addition, radishes provide complex carbohydrates, dietary fibre often organic nutrients and minerals to humans, (El-Ramady et al. 2015).
Omics approaches using Next Generation Sequencing (NGS) methods provides a large amount of genomic study (Wang et al. 2013), enables identifying new genes and sequences and positional markers to be obtained and distributed on the chromosomes (Kim et al. 2019). In addition, genome-wide study results reveal the genetic causes of diverse characteristics (Kobayashi et al. 2020). Genome-wide exploration of suitable markers and higher-throughput genotyping will also be achieved by re-sequencing genomes (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4885859/; Kobayashi et al. 2020). Furthermore, there is less studyhas been published that discusses the historical milestones and technological advancements in radish breeding. As a result, we have gathered information on different elements of radish breeding and its numerous accomplishments in this section. We believe that this study will prove to be a valuable resource for vegetable breeders in the future.

Breeding Goals
the Brassicaceae family is its high nutrition content, health benefits conferred by its chemical compounds, and a significant contribution to the human being (Al-Shehbaz 2001). Root length is an important trait of radish for consumers, and preference always goes to radish on length, diameter, and color; visual indicators such as the color of the label and where it is presented are crucial to buyers' selection phase. Too many experiments have concentrated on gene mapping to classify significant color-gene associations in various vegetables for this cause . Productive radish root color is vital to radish crop productivity, the discovery and detection of large plant genes involved in radish colouring º 3 would aid in the advancement of color genetics (Schreiner et al. 2002). To date, the range of potential skin inheritance trends has been investigated extensively in radish (Yarnell 1956). Gamba et al reported that 609 chemical compounds within 23 categories of most studied varieties of Radish, such as Red (30%), white (13%), and black (6%) (Gamba et al. 2021). This study also found that nutrients, antioxidants, and phytochemicals mainly identified in roots, sprouts, and leaves, which could be considered an important part of a healthy diet (Gamba et al. 2021).
In addition, researchers have focused on red radish with red flesh because it contains large amounts of a natural red pigment widely used in foods, wine, and cosmetics (Jing et al. 2012). The uniformity of various color, size, and yield are the factors becoming a high priority goal in radish breeding (Elsayed et al. 2016). Radish has a wide variety of colours that affect its appearance and its nutritional quality . However, the detection, identification, and quantification of flavonoids in multicolour radish are rarely explored. Whereas Zhang et al. (2020) identified that red and purple radishes contained similar anthocyanin compounds responsible for color pigmentation, including red cyanidin, callistephin, and pelargonin . Purple ZJL contains cyanidin o-syringic acid, and cyanin, whereas callistephin and pelargonin contains more amount in dark red TXH. The metabolites in colored radishes that differed from SZB genes are broadly involved in the plant secondary metabolites biosynthetic pathway, such as flavonoid, flavone, isoflavonoid, and phenylpropanoid biosynthesis. This approach would be useful for cultivating important and valuable new radish varieties .
To investigate growth, yield, and qualitative parameters of radish and of its varieties (Pusa Desi, Pusa Himani, Pusa Reshmi, Pusa Chetaki, Arka Nishant, Japanese White and IHR-1-1) were used in the study. It was found that total fresh weight of plant (190.06 g to 226.60 g) was observed in variety Arka Nishant, whereas minimum in variety Pusa Desi (Dongarwar et al. 2018). These results explain anthocyanin synthesis in radish and provide potential genetic clues for improving anthocyanins in radish roots (Giusti and Wrolstad 1996). A pathogen could damage harassment of yield, and in root color, these varieties would not be preferred for the consumer. Fusarium wilt (FW) is vascular wilt soil-borne disease and caused by fungal pathogen Fusarium oxysporum f. sp. Raphanin, causes severe yield losses in the production of radish (Bosland 1988). The most emerging effective method to control the FW by using resistant varieties in crop improvement (Fita et al. 2015). Fusarium-resistance is highly studied among 'Motohashi-' or 'Kuroba-mino' lines of Minowase variety and Tosai' is the strongest line among Nerami varieties (Hida and Ashisawa 1985). it was found that providing good quality of seed and accurate quantity of seed would increase the yield of radish (Baksh et al. 2006). To treat several diseases, bioactive compounds in Raphanus sativus (radish) is being studied, and therefore, radish has attracted scientific attention due to its nutritional and phytochemical composition, which reduces the risk of developing many cancers and cardiovascular diseases (Lima et al., 2008). Further, the important goals are provided in the Moreover, salinization is considered as one of the major soil pollutions in the environment affecting plant growth and soil fertility globally (Shrivastava et al. 2015) This scenario alarms an urgent need to enrich the soil or to identify stress-tolerant plants. It is reported that antioxidant enzymes (HOD-Hydrogen Peroxide; SOD-Superoxide; LOD-Lipid Peroxidation; CAT-Catalase) plays a major role in reducing the effects of salts in plants by monitoring the oxidative stress in them (Vishnu-Priya et al. 2020). To study the salt tolerance of Japanese wild radishes called 'Hamadaikon' (Raphanus sativus f. raphanistroides Makino) and its characteristics like seed germination, plant height, root length and fresh weight were examined under the salinity condition, and it was found that higher germination and growth in NaCl were shown at 25 o C than those at 20 o C (Sugimoto 2009). Hence, the wild radishes could be considered for the salt tolerance breeding. Moreover, halopriming is a seed priming technique in which the seeds were soaked in various salt solutions enhances germination and seedling emergence uniformly under adverse conditions. The effect of halopriming on germination, initial growth and development of radish under salt stress conditions was studied. It was found that the best effect was achieved by priming with CaCl2 for germination characteristics and vigour and with KCl for initial development (Kanjevac et al. 2021 (Bateman 1955). Regular flowering appears from three florets on the tip of each branch of the panicle and each flower is effective in producing a pod upto1 to 3 inches long and consists of one to six seeds (Bailey 1949). The radish flowers open in the morning with the fresh corolla and remain until the next day (Kremer 1945). Kremer also reported that pollen receptivity of the flower limits upto few hours a day. Its flowers are 1.5-2 cm in width, whitish to pinkish and purplish colour with purple veins, and have four erected sepals and clawed petals, six stamens and 3-4 cm long style (Nishio 2017;Nayik et al. 2020). Siliqua or seedpod, a type of seed capsule of radish, is 1.5 cm wide and 3 to 7 cm long, consisting of 6-12 seeds/pod with a long conical seedless beak . The inflorescence of radish is a typical elongated, erected, an oblong raceme of Cruciferae (Kercher and Conner 1996;Gopalakrishnan 2007). The study of pollination of radish was carried out by Crane and Mather (1943), Kremer (1945), and Radchenko (1966). The main objective of the investigation was the cross-pollination of radish by Crane and Mather (1943), who found that the 'Icicle' and 'Scarlet Globe' cvs were self-incompatible pollinated with the help of honeybees (Young and Stanton 1990). The studies indicated that the seed yield is greatly influenced by the number of honeybees striking the radish flowers (Kremer 1945). Radchenko (1966) also reported that honeybees were the main pollinators of radish flowers, approximately 77 to 99 percent in total, increasing the crop yield by 22 percent and enhancing the seed quality. Therefore, radish is considered as almost entirely insect-pollinated (Jones and Rosa 1928). During fruit maturation, the color of seeds is somewhat yellow that turns reddish-brown with age (Kalia 2005;Lim 2015). The mature radish leaves are alternate and arranged in a rosette pattern and have a lyrate shape that is set apart pinnately with an enhanced terminal lobe and minor lateral lobes (Gopalakrishnan 2007). A longer root form, including oriental radishes, daikon or mooli and winter radishes, grows up to 60 cm (24 in) long with foliage about 60 cm (24 in) high with a spread of 45 cm (18 in) (Brickell 1992).

S haplotype
Radish is a self-incompatibility crop exhibit the high heterosis, production of F1 hybrids based on self-incompatibility are desired to get rid of laborious hand emasculation in radish (Nishio and Sakamoto 2017). The main aim of a plant breeder is to identifythe breeding lines of S haplotypes. The plant breeder can avoid the cross incompatibility of the parental lines . The S haplotype of each parental line need to show the compatible reaction between parental lines, therefore for producing F1 hybrid breeding, it is very important to identify the S haplotypes of parental lines (Nou et al. 1993;Ockendon 2000). The abundance of S haplotype determines a specific S haplotype by using traditional methods including test cross method, pollination, isoelectric focusing, immunoblot analysis, and the pollen tube fluorescence analysis (Ruffio-Châble et al. 1997;Georgia et al. 1982;Martin 1959). The S alleles are highly variable in S haplotype (Ockendon 2000). Moreover, Nikura and Matsuura identified 37 alleles in Radish (Nikura and Matsuura 2001).
Several S haplotypes in Raphinus sativus were identified based on polymorphism in SLG, SRK and SCR/SP11 sequence and S haplotypes are numbered as S-1, S-2, S-3, etc (Nikura and Matsuura 2001; Takeshi and Sakamoto 2017). Although radish belongs to a genus different from Brassica, nucleotide sequences of SP11, SRK, and SLG alleles of radish and Brassica are intermingled in phylogenetic trees of SP11, SRK, and SLG, respectively, indicating that diversification of these alleles predates speciation of º these genera . SP11, SRK, and SLG alleles of some S haplotypes in radish are highly similar to those of some S haplotypes in Brassica, and one S haplotype in radish has been revealed to have the same recognition specificity as that of one S haplotype in B. rapa . Comparison of nucleotide sequences of SP11 and SRK alleles and recognition specificities between similar S haplotypes of radish and Brassica may provide valuable information for understanding the molecular structures of SP11 and SRK proteins. However, researchers' numbering of S haplotypes in radish varies, and nucleotide sequence information on S haplotypes is thus confusing (Nishio and Sakamoto 2017).
Besides, analysis of SLG and SRK is utilized to identify S haplotype in Raphanus and Brassica by the using methods polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) (Lim et al. 2002;Nishio et al. 1997;Okamoto et al. 2004). However, the own limitation of PCR-RFLP, first, it is difficult to design a universal primer that can amplify SLG and SRK alleles; second, the presence of multiple genes homologous to the SLG or SRK genes in Brassicaceae plants aggravates PCR amplification of specific SLG or SRK alleles (Lalonde et al. 1989;Boyes et al. 1991;Kumar and Trick 1993;Suzuki et al. 1997;. Additional advanced radish cultivars (cultivars with improved yield and higher quality) were also produced by the Ogura CMS method to assist in radish hybrid , this variety shows such as bulk selection, mixed mass pedigree selection, or bud pollination will take eight to twelve years to produce a new variety, new varieties must be produced from other genetic means (Cox and Beaton 2020).

Interspecific hybridization
Inter-specific and intra-specific hybridization has an important role in genomic study and crop improvement by introducing desirable agronomic characters and specific traits such as disease, insects and stress resistance from wild species to cultivated ones (Bowely and Taylor 1987;Kaneko and Woo 2014). Jin et al, 2020, observed thatthe crosses between radish, turnip, and Chinese kale were made to produce F1 hybrids (Jin et al. 2020). The study indicated that the average podding rate of the cross between radish and turnip (67.03%) was much higher than that of the reciprocal cross between turnip and radish (55.04%) (Jin et al. 2020), and it was also reported that the average seed-setting rate and hybrid acquisition rate of the radish and turnip based on cross pattern (e.g., 2.25% and 0% respectively), however, seed production of the F1 hybrids and their F2 progeny was up to 0.4% and 2%, respectively, as compared to wild radish (Darmency et al. 1998). Therefore, the study indicated that there was a low hybridization affinity between radish and Chinese kale, but incompatibility still prevailed (Jin et al. 2020).
Similarly, the radish-wild mustard interspecific hybrid was studied. It was found that production was higher with radish pollen competition, i.e, 42 and 3 interspecific hybrid seeds per 1000 seeds were observed (Eber et al. 1998). Another study by Peter et al indicated that the modified flower culture method is the best method for hybridization between radish and (transgenic) oilseed rape (Raphanobrassica hybrids) without labour-intensive production vitro ovule or embryo rescue techniques. This is a potential approach for breeding programs by introducing useful radish genes, e.g., nematode resistance genes, into oilseed rape (Metz et al. 1995). Moreover, clubroot is a common disease of cabbages, cauliflower, radishes, turnips, and other plants of the family Brassicaceae caused by Plasmodiophora brassicae (Bhattacharya et al. 2014). Radish is a close relative of the brassica family, and it was found that a synthesized allotetraploid Brassicoraphanus (RRCC, 2n = 36) between R. sativus cv. HQ-04 (2n = 18, º RR) and Brassica oleracea var. alboglabra (L.H Bailey) (2n = 18, CC) proved resistant to multiple clubroot disease pathogen P. brassicae causing club root disease (Zhan et al. 2017).
However, the spontaneous hybridization event between Brassica napus (oilseed rape) and Raphanus raphanistrum (wild radish) was screened, and it was found that hybrids with wild radish as the seed parent contributes for herbicide resistance belonging to rape. Another study by Darmency et al, 1998, indicated that wild radish in an oilseed rape field produced as many as three interspecific hybrids per 100 plant and was the first-ever such report of such a spontaneous event (Darmency et al. 1998).

Molecular Markers to QTLian Breeding
Several economically important traits in radish are being identified, these traits are yield, insect resistance and disease resistance (Kaneko and Matsuzawa 1993). = Yield is a complex trait governed by the polygenic characters, to identifythese traits using conventional breeding/traditional breeding is difficult because these traits depend on phenotypic expression and have environmental and genotypic interaction. These problems are overcome by the new tool molecular breeding, identification of quantitative trait is being utilized with the help of DNA markers (Kaneko et al. 2007) and linkage mapping (Xu et al. 2012), there are several DNA marker are being utilized in breeding programme such as restriction fragment length polymorphism (RFLPs), random amplified polymorphism dna (RAPD), simple sequence repeats (SSRs), single nucleotide polymorphism (SNPs) (Muminović et al. 2005, Xu et al. 2012, Budahn et al. 2009. Molecular markers such as RAPD have been used to establish the origin of hortensis var. sativus and var. niger, which formed from distinct progenitors and came from different sources (Curtis 2011). Several Asian varieties show greater skin and flesh color, size, length, and weight of roots, var. hortensis' genetic variability is also not a surprise.
Moreover, Lee et al. (2021) performed genome-wide association studies (GWAS) using genotyping-by-sequencing (GBS) for identifing FW resistance loci followed by Phenotypic studies conduction (Lee et al. 2021). The GWAS analysis identified 44 single nucleotide polymorphisms (SNPs) and twenty putative candidate genes that were significantly associated with FW resistance. A total of four QTLs were identified from F2 population derived from a FW resistant line and a susceptible line, among these one of which was co-located with the SNPs on chromosome 7. These markers are emerging tools for molecular breeding programs and marker-assisted selection to develop FW resistant varieties of R. sativus (Lee et al. 2021). Moreover, for identification of disease Fusarium wilt, Yu et al. 2013, constructed a genetic linkage map on the F2 population, they observed total 8 loci conferring FW resistance that were distributed on 4LGs, namely 2, 3, 6 and 7 of the Raphanus genome. Synteny analysis using the linked markers QTL showed homology to A. thaliana chromosome 3, which contains disease-resistance gene clusters, suggesting conservation of resistance genes between them. The list of important QTLs is identified in the radish and their location is provided in the Table 1 Moreover, identification of root shape and red pigmentation is done by the , they observed that three quantitative trait loci for root shape, namely, LG3, LG8 and LG9, two QTLs for root diameter, namely LG4 and LG8 and one for red pigmentation is identified with the help of using AFLP, SSR and SLG-CAPS . Kamei et al. 2010, constructed a genetic linkage map using AFLP and SSR markers and concluded that CR is governed by the single gene or closely linked gene loci namely, º 14 Crs1, Crs2 and Crr3 (Kamei et al. 2010). A genetic map was constructed using an F2 population by using markers SRAP, RAPD, SSR, ISSR, RAMP and RGA markers, and they found that a novel QTL qRCD9 is responsible for controlling root CD (Xu et al. 2012). Resistance against cyst nematode (Heterodera schachtii) was identified by using RAPD, dpRAPD, AFLP and SSR markers (Budahn et al. 2008). To identify quantitative traits in radish for morphological characters namely, ovule number per silique, seed number per silique, plant shape, pubescence, whole plant weight (g), upper part weight (g), whole root weight (g), main root weight (g) using recombinant inbred lines, they identified 8 and 10 quantitative traits in 2008 and 2009 respectively ). In the identified QTL regions, nine SNP markers were newly produced. Nucleotide sequences and expression of these genes suggested their possible function in 4MTB-GSL biosynthesis in radish roots. (Zou et al. 2013). Whereas Fan et al. (2020) discovered that the R2R3-MYB transcription factor responsible for anthocyanin pigment 2 (PAP2) production is located on chromosome 2. The amino acid sequence encoded by the RsPAP2 gene was entirely distinguishable from other previously published different RsMYB genes responsible for the red skin color of radish.

Genomics
Genomics is now at the core of crop improvement, and radish crop has been exploited to study the underlying differences in genotypes. The rapid development of genomic data boosted the discoveries regarding the genetic basis of plant traits, such as increased yield, flowering, or disease resistance (Tuberosa and Salvi 2006). A variety of systematic studies of the radish have investigated their genomes' arrangement and the reorganization of chromosomes during polyploidy events , of which draft genomic sequences has been assembled (Kitasiba et al. 2012). Another study reported an Asian radish cultivar, WK10039 which was sequenced entirely by combining 454, Illumina, and PacBio sequencing systems and bacterial artificial chromosome clones obtained through end sequencing, was fully sequenced by using the end sequencing method and sequencing equipment from the ABI firm (Jeong et al. 2016), over the last decade, a variety of genomic studies on the cultivated radish have been performed (Jeong et al. 2014). Moreover, a chromosome-scale genome assembly (rs1.0) of WK10039, an Asian radish cultivar, and compared it to assemblies documented previously was constructed (Mitsui et al. 2015). It revealed more details than those previously recorded (having greater coverage of the genome, a greater number of contigs, and chromosome anchoring) (Lee et al. 2018). However, Radish Base is a genomic and genetic database that currently contains radish mitochondrial genome sequences . This database presently includes the mitochondrial genomes of two newly sequenced radish species, one from the normal cytoplasm and the other from the male-sterile cytoplasm of Ogura (Tanaka et al. 2012). The previous study published the bioinformatics analysis in radish and identified 20 COL transcription factors in the radish genome among 54,357 coding genes (Hu et al. 2018). Every COL ene in the 'Aok i daikon' c lti ar was matched with the corresponding COL ene in the 'kaz sa' c lti ar. A total of 20 radish COL genes were also searched in the c lti ar 'WK10039' (H et al. 2018). Besides, in radish genome, thirty-five unique RsOFPs and five RsOFP-likes (with no/partial OVATE domain) were identified by BLASTP and analysis of exonintron organization revealed that most genes were intron-less contains maximum coding sequences in the genome (Hu et al. 2018) In addition, R.sativus inbred line XYB36-2, a 119.75 Gb of whole-genome shotgun sequences were performed using a HiSeq2000 system (Xiaohui et al. 2015). On the basis of 17-mer analysis, the estimated size of genome came out to be 530 Mb. A 387.73 Mb was assembled into 44 820 high-quality scaffolds using SOAP denovo  and SSPACE (Boetzer et al. 2011). The assembly in this study showed excellent results with fosmid clones (98.86% covered), the assembly showed a much higher quality than the draft genome of R. raphanistrum (254 Mb contigs) (Moghe et al. 2014) and two assemblies (116.0 and 179.8 Mb) of R. sativus 'Aok i' (Kitashiba et al. 2014, ) which was released previously. After de novo assembly of the 'Okute-Sakurajima' genome, an estimated haploid genome size of 498.5 Mb was found. The de novo assembly showed a substantially heterozygous genome . Subsequent long-read sequencing produced 36.0 Gb data (60.7 coverage of the estimated genome size) in 2.3 million reads with N50 length of 29.1 kb. After two rounds of data polishing, the long-read assembly consisting of 504.5 Mb primary contigs (including 1,437 sequences with an N50 length of 1.2 Mb) and 263.5 Mb alternative contigs consist of the other haplotypes with different alleles, also known as haploid sequences (including 2,373 sequences with an N50 length of 154.6 kb) (Shirasava et al. 2020).
Study performed on the radish genome after polyploidy has shown fundamental information about the radish genome production and evolution, which provides valuable insights into radish genetics and breeding (Yu et al. 2017). The detailed data and genomic methods obtained through these investigations support a greater understanding of the radish triplicated genome composition. Additionally, these methods help radish breeding by promoting the usage of marker-assisted collection, comparative genomic studies, and the transmission of knowledge from the reference data to other radish accessions (Varshney et al. 2021). Consequently, a portal that is home to considerable quantities of genomic information and various links to specific genome analysis methods is extremely valuable in radish research and breeding.

Genetic Engineering
Genetic engineering has pvotal role in agriculture by improving characters in the crops and satisfying the need of poor nourished countries. The Developments in gene technology and metabolic engineering systems accelerated the production of useful germplasms (Wang et al. 2017). The Progress is being achieved in plants methods by improving the traits; researchers have successfully produced transgenic radishes with various agronomic characteristics (Curtis and Nam 2001). Some radish varieties exhibit favorable traits, including improved yield, and transfer of these characteristics on to the host plant (Tzfira and Citovsky 2008;Lacroix and Citovsky 2019).
Gene transmission is done with the help of pathogen, known as agrobacterium, is extensively used as a technique for plant hairy root lines, which appear to yield better than other forms of root systems (Ali et al. 2008). Herbaceous hairy roots have advantageous due to their longevity, pace of growth, and capacity to assist plants in growing from the root up (Gelvin 2009). The hairy roots are produced in nutrient solution with the help of growing agrobacterium that contain unusual properties, including biochemically and biotransforming different metabolites. It is best to use Agrobacterium to produce secondary metabolites since they help to enhance the growth regulators (Giri and Narasu 2000). Working on the hairy roots, it can be discovered new sources of natural compounds (Berkov et al. 2003), In addition, chromosomal disruption or amplification may affect the fertility of cultured plants. Antibiotics, herbicides, metabolic analogues, and non-toxic agents all facilitate transformed cell for survival. Kanamycin and hygromycin B hamper radish regeneration (Curtis et al. 2004).
Recent advancements in plant biotechnology indicate that radish could be genetically modified via a process called "floral-dipping." This technique involves co-suppression of the photoperiodic gene º GIGANTEA in radish and contributes to the plant's ability to delay bolting and blooming. It can be used for boosting a crop's medicinal value (Curtis 2003). The prospects for improving transformation efficiency and selecting new traits for generating late-flowering radish are published (Curtis et al. 2011). In 2001 was demonstrated that plants derived from plants dipped into an Agrobacterium suspension containing both the beta-glucuronidase (gusA) gene and the herbicide resistance gene (bar) between the flanking T-DNA border sequences could be used to generate transgenic radish (Raphanus sativus L. longipinnatus Bailey). (Curtis and Nam 2001). At the end, Southern blotting results revealed that both the gusA and bar genes integrated into the genome of transformed plants and segregated as dominant Mendelian traits (Curtis and Nam, 2001). A study revealed that The RHA2b gene from radish encodes a transcription factor involved in abscisic acid (ABA) signal transduction and is responsible for seed dormancy and preharvest sprouting (Li et al. 2019). The study performed the experimentation in which The RsRHA2b gene was cloned and transferred into Zhengmai 9023 via Agrobacterium-mediated stem apex transformation (Li et al. 2019). The agrobacterium-mediated transformation became a more appropriate method for genetic transformation (Hayta et al. 2019). The use of adventitious shoot growth on hypocotyl explants for Agrobacteriummediated radish genetic transformation was investigated using transgenic radish (Raphanus sativa L., cv. Jin Ju Dae Pyong) grown on Murashige and Skoog medium (Cho et al 2008). Besides, northern blot results revealed the GUS gene transcript was detected in few regenerated plants hence, confirming genetic transformation (Cho et al. 2008).
In addition, the techniques available for introducing pharmaceutical proteins into radish for on-site delivery of edible proteins into it is discussed by Curtis in his study (Curtis 2003). The concerns of releasing transgenic radish to the field in pollen-mediated gene transfer have also been explored. Risks that might exist and the introduction of transgenic radish to the field are sometimes brought up in discussions about transgenic crops (Curtis and Nam 2001;Rissler et al. 1996;Snow and Palma 1997).

Conclusion and Future Directions
The production of yields, early maturity and late bolting, pungency, cold hardiness, drought resistance, heat tolerance, and soil adaptability are just a few of the essential radish breeding traits. The radish genome contains self-incompatibility alleles, allowing for the generation of F1 hybrids without the labour-intensive and without hand emasculation required in radish. When generating F1 combinations, it is critical to determine the S haplotypes of the parental lines to avoid hand emasculation. For successful production of radish yield, inter-and intra-specific hybridization are vital to genetic research and crop improvement because they enable the introduction of desirable agronomic traits into the population. Collecting complete genetic data on chromosomes as well as information on inheritance is critical. To better understand and forecast resistance, yield characteristics, and fruit quality, researchers must understand the regulatory factors that synchronize at various developmental stages for each of the attributes discussed. It remains necessary to develop a robust and long-lasting strategy for plant disease resistance, which is currently under consideration. This is because diseases are capable of evading resistance by generating novel bacterial strains.
Due to the completion earlier this year of large-scale sequencing of the radish genomes, scientists will now have precise information on disease resistance genes for a variety of diseases and genes encoding critical biochemical properties of the plant. Speed breeding is one such strategy; as the cost of genome sequencing continues to decline, RAD-sequencing and DNA microarrays will become more common, º enabling faster genome mapping and tagging of new quantitative trait loci. These quantitative trait loci (QTLs) may incorporate resistance into high-yielding radish genotypes and combine them with significant resistance genes to increase the number of resistant radish genotypes. Additionally, GWAS (genome-wide association studies) can map characteristics to specific candidate genes on a genome-wide scale to improve crop production and quality in radish. The discovery of significant genetic and metabolic diversity paves the way to develop controlled harvest variations in agriculture and genetic enhancement via breeding. º º º º º