**2. Breeding goals**

Radish is high in its nutrition content, health benefits conferred by its chemical compounds and a significant contribution to the human being [20]. Root length is an important trait of radish for consumers, and preference always goes to radish on length, diameter and colour; visual indicators such as the colour 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 colour-gene associations in various vegetables for this cause [21]. Productive radish root colour is vital to radish crop productivity. The discovery and detection of considerable plant genes involved in radish colouring would aid in advancing colour genetics [22]. The range of potential skin inheritance trends has been investigated extensively in radish. It was reported that 609 chemical compounds are present within 23 categories of the most studied varieties of Radish, such as red (30%), white (13%) and black (6%) [23]. This study also found that nutrients, antioxidants and phytochemicals are mainly identified in roots, sprouts and leaves, which could be considered an important part of a healthy diet [23]. 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. The uniformity of various colours, sizes and yields are the factors becoming a high-priority goal in radish breeding [24]. Radish has a wide variety of colours that affect its appearance and its nutritional quality [25]. However, the detection, identification and quantification of flavonoids in multicolour radish are rarely explored. At the same time, it was also identified that red and purple radishes contained similar anthocyanin compounds responsible for colour pigmentation, including red cyanidin, callistephin and pelargonin [26]. Purple ZJL contains cyanidin *o*-syringic acid and cyanin, whereas callistephin and pelargonin contain more amount in dark red TXH. The metabolites in coloured 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 [26, 27]. These results explain anthocyanin synthesis in radish and provide potential genetic clues for improving anthocyanins in radish roots [28].

Fusarium wilt (FW) is a soil-borne vascular wilt disease caused by fungal pathogen *Fusarium oxysporum* f. sp. Raphanin, causes severe yield losses in radish production [29]. The most effective method to control the FW is using resistant varieties in crop improvement. Fusarium resistance is highly studied among 'Motohashi-' or 'Kuroba-mino' lines of the Minowase variety, and Tosai' is the strongest line among Nerami varieties [30]. A pathogen could damage harassment of yield, and in root colour, these varieties would not be preferred for the consumer. Bioactive compounds in *R. sativus* (radish) are being studied to treat several diseases. Therefore, radish has attracted scientific attention due to its nutritional and phytochemical composition, which reduces the risk of developing many cancers and cardiovascular diseases. Further, the important goals are provided in **Figure 1**.

Moreover, salinisation is considered as one of the significant soil pollutions in the environment affecting plant growth and soil fertility globally [31]. 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) play a major role in reducing the effects of salts in plants by monitoring the oxidative stress in them [32]. To study the salt tolerance of Japanese wild radishes called 'Hamadaikon' (*R. sativus* f. raphanistroides Makino) and its characteristics such as seed germination, plant height, root length and fresh weight were examined under the salinity condition. It was found that higher germination and growth in NaCl were shown at 25°C than those at 20°C [33]. Hence, wild radishes could be considered for salt tolerance breeding. Moreover, halopriming is a seed priming technique in which the seeds were soaked in various salt solutions to enhance germination and seedling emergence uniformly under adverse conditions. The effect of halopriming on germination, initial growth and development of radish

**Figure 1.** *Breeding goals of radish (Raphanus sativus L.).*

under salt stress conditions was studied. It was found that the best outcome was achieved by priming with CaCl2 for germination characteristics and vigour and with KCl for initial development [34].
