Agricultural modifications have shifted the paradigm of consumer acceptance. Traditional extrinsic visual-quality attribute awareness has moved to intrinsic attributes. Nutritional, functional, and physio-chemical factors of fruits and vegetables have been magnified in public awareness. These factors comprise the essential vitamins, minerals, phytochemicals, and antioxidant content traits introgressed. The dynamic genotypic and environmental factors determine the above attribute along with handling post-harvest. Post-harvest loss has been a major bottleneck, and a struggle to diminish the yield gap by improving the nutritional toolbox for genome editing to feed the growing population. The economic and social burden of the loss prompts the potential of the new-editing tools. It must be exploited alongside the conventional ones that have been limiting success. Due to their effectiveness and specificity of cleavage recognition sites, either by RNA-directed SDNs or protein-directed SDNs, site-directed nucleases (SDNs) utilized in plant editing technologies are frequently used to modify genomes. It includes meganucleases, ZFNs, TALENs, and CRISPR/Cas used to achieve random, predicted, or precise insertion. These all accomplish precise genetic alterations by causing deliberate DNA double-strand breaks (DSBs) (Tripathi et al., 2021). Additionally, CRISPR can avoid other obstacles, including sterility, self-incompatibility, high heterozygosity, a low frequency of recovering desirable alleles and features, and long life cycles that make conventional breeding operations more difficult or impossible to complete (Shipman et al., 2021). With the easy elimination of undesirable traits, the in-depth investigation of non-interference about the constitutive genome editing on other cellular functionality has increased. To avoid any pleiotropic changes on regulatory genes, Somatic mutations can be generated by special promoters in specific cells, tissues, and organs of the plant genome using the CRISPR- TSKO (tissue-specific knockouts), or TSGE (tissue specific gene editing) were preferred. It generated more accurate KO (knock-out) variants in plants. DJ3S, p54/1.0—Cassava promoters targeted into root of Carrot and Arabidopsis (Singha et al., 2022). Similar to this, another gene-editing method regulates the production of the Cas protein in fruits using an inducible chimeric transcription factor (XVE). The activator is an assembly of bacterial repressor LexA(X), activating domain VP16(V), and regulatory region of human estrogen receptor (E) (Brand et al., 2006). The estradiol-induced XVE is an inducible expression system used in transgenic apples, tobacco, Arabidopsis (Zuo et al., 2001), and soybeans for reporter gene expression and overcoming certain limitations in other expression systems (Corrado and Karali, 2009). The outcomes of repair mechanisms chosen for genome editing applications that include site-directed nuclease-1 (SDN1) in kiwi-fruit (ACC oxidase) produce non-homologous end products after the cleavage of host DNA by CRISPR/Cas9. Non-homologous end joining (Brand et al., 2006). The outcomes of repair mechanisms for genome editing include site-directed nuclease-1 (SDN1), producing non-homologous end products after the cleavage of host DNA by CRISPR/Cas9. NHEJ causes indel mutations by gene silencing, gene inactivation, and gene knockout. SDN2 utilizes the plant Homology-Directed Repair (HDR) pathway to modify the gene’s activity by altering the sequence. The SDN2 techinique uses template DNA to produce an intended sequence modification at the DSB site. SDN3 technique uses a DNA insertion or substitution at a specific site in the DNA. Base and prime editing techniques are a type of SDN1 type. They can generate change in nucleotide without deploying a DSB or template DNA insertion in the locus targeted (Lin et al., 2020). The modifications of base and prime editing are comparable to the SDN2 technology. Oligo-directed mutagenesis (ODM) alters the genomic locus by targeted mutations. Successful application of ODM has been done on maize (Zhu et al., 2000), rice (Okuzaki and Toriyama, 2004), and oilseed rape (Gocal et al., 2015). The approach of SDN1, SDN2, and ODM targets mutation without the inclusion of exogenous DNA. But the SDN3 aims to target exogenous DNA insertion of various lengths (Modrzejewski et al., 2019). The delivery system of the SDNs includes PEG-fusion, electroporation, and biolistics, whereas, without the aid of any expression system. The chemically synthesized oligonucleotide used in ODM is supplied directly to the plant cell (Sandhya et al., 2020). However, the most reliable transformation for gene-editing is the Agrobacterium-mediated delivery in plants. Another approach to altering gene expression through DNA methylation has also been approached in orange and bell pepper (Cheng et al., 2018). Alongside genome editing, the combination of big data modeling and artificial intelligence (AI) monitoring has changed the course of field challenges. Most of the gene-editing tools has been researched on tomato and then progressed to achieve in several other fleshy fruits discovering numerous candidate gene targets (Rehman et al., 2022). Browning reactions in fruits post-harvest has also been triggering loss to the food industry. Potential research on natural bioactive compounds with anti-browning extracts (mangrove, green tea, thyme, pineapple) has been achieved to replace chemical additives by genome editing. An industrial approach for regulating the challenge has been worked through the activity control of the Polyphenol Oxidase (PPO) enzyme (Moon et al., 2020). Innovations targeting manipulation in the genome of plants have been extensively investigated and achieved at a spellbinding pace. ONM (Oligonucleotide directed mutagenesis), and ENs (Engineered nucleus) have been traditionally practiced and have been revolutionized with ZFNs, TALENs, EMNs, mi-RNA, and CRISPR. Modulation in the PPO and POD genes with miRNA, and CRISPR knock-out mutation reduced the browning activity in eggplant berries by 52% on the SmelPPO4-5-6 gene (Maioli et al., 2020). Verification has been done by HRFA (High-Resolution fragment analysis) on the T1 phenotypic lines generated (Hamdan et al., 2022). The post-harvest storage also critically implicates the quality and shelf-life of freshly harvested fruits. The pathogenic microbes and pests in favorable growth conditions cause two types of deterioration: 1) physiological-softening, ripening, and senescence and 2) microbial deterioration by fungal or bacterial growth. Therefore, optimized storage conditions with CA (controlled atmosphere), DCA (dynamic controlled atmosphere), or ULO (Ultra-low oxygen) have been evaluated as chemical-free storage. Apart from the storage conditions, chemical treatments of pesticides have been used against the microbial activity. The implications of the hazardous by-products and residues have reduced their demand for usage. Comprehensive research has developed alternatives to chemical treatments using the physical-natural blend. Led light treatment, essential oil application, and edible coating (EC) are a few examples (Sánchez-González et al., 2011). EC is a semipermeable film over the fresh stock of perishable produce that has been catching attention for extending post-harvest life (Fawole et al., 2020). EC preserved fruit quality of ripening, softening, colour transformation, formation of sugar, and loss of organic acid by lowering the exchange of gaseous metabolic process in plants (Ziv and Fallik, 2021). Exploration of enzymatic inhibitors, nano and microencapsulation of the bioactive compounds is the need of the hour for implementing techniques to improve and utilize the natural extracts. Extensive broad-spectrum research on protein and gene expression profiles would also determine its biochemical, physiological, and receptor signaling activity pathways. This will help generate the required information about the natural extract’s target and through efficient statistical approaches, it can be effectively used on a large scale. Genome editing on fruits has dissected an imminent network of signaling and biological pathways that is anticipated to aid in investigating hitherto undiscovered genes inducing positive post-harvest phenotypes (Table 1).

There is currently a great deal of attention on the health advantages of consuming vegetables of the expansive array of nutrients found in them, such as vitamin supplements, minerals, antioxidants, dietary fiber, and phytochemical compounds (Septembre-Malaterre et al., 2018). Vegetables, whether consumed fresh or in processed form, defend against a wide range of non-transmitted diseases and assist in the reduction of such food insecurity in underdeveloped countries (Desjardins, 2014). Food losses and waste reduction are crucial to a country’s food security as intensive and extensive farming. Losses reduce the availability of food, contributing to food insecurity and waste food generating unnecessary emissions of CO₂ as well as a failure of the food’s economic value. As a result, limiting post-harvest losses in agricultural products is critical for food availability and security in developing countries. Post-harvest losses are losses in the nutritional value, seed viability, and selling price of food that occur along the entire food supply chain, from harvest to consumption (Ghosh et al., 2011). Genome editing allows for the acquisition of multiple homozygous mutations in a single generation without foreign DNA, opening up new avenues for genomics and the breeding of crops and quality traits in vegetables. The tomato and potato have attracted the most focus on genome editing research and implementation.

The ability to alter important characteristics in cucumber, watermelon, lettuce, and broccoli has been demonstrated (Cardi et al., 2017). In tomato seeds, gene LEAFY-COTYLEDON1-LYKE4, that encodes the β -subunit of the transcription factor Y, is damaged by the transiently expressed zinc finger nucleases (ZFNs). Plants with mutations displayed a wide range of morphological changes as well as the expression of genes involved in hormone metabolism, especially the ethylene biosynthetic pathway. No off-target changes were found in the closely linked L1L2 and L1L3 gene sequences (Hilioti et al., 2016). GABA (Y-aminobutyric acid) is a chemical that promotes health and has received a lot of attention in traditional tomato breeding research. Using genome editing, multiple GABA pathway genes were modified, resulting in a 19-fold increase in GABA content in Solanum lycopersicum. Resistance to diseases through genetic modification is another new area of study in vegetables rapidly expanding as the CRISPR/Cas system as a genome editing tool. Genetically modified by deletion of 48 base pair in homozygous layout in MLO1 locus, tomato plants generated which showed resistance to powdery mildew disease affected by Oidium neolycopersici (Erpen-Dalla Corte et al., 2019). Editing the SIDMR6-1 gene also produced bacterial disease resistance (downy mildew resistance 6 gene) (Tripathi et al., 2020). The shift in the recent paradigm of abiotic stress tolerance research includes more horticulture crops for genetic modification. Significant advances have been made in the improvement of biotic stress tolerance (fungal infection and virus resistance) as in tomatoes and cucumbers (Jain, 2015; Shi et al., 2017). Multiple research studies have pivoted the potential functions in plant protection against abiotic and biotic stresses, as well as improving fruit quality, plant architectural features, and storage stability (Kulus, 2018). The N′ and C′ ends of eIF4E-were targeted by CRISPR/Cas in cucumbers by agrobacterium-mediated transformation, leading to resistance to cucumber vein yellow virus, pumpkin mosaic virus, and papaya ring spot mosaic virus (PRSV-W) (Chandrasekaran et al., 2016). Numerous diseases are brought on by fungi, which can significantly reduce crop output and quality. For example, downy and powdery mildew significantly reduce tomato production (Borrelli et al., 2018). CRISPR/Cas9 knockout of DMR6 homologous genes in tomatoes demonstrated resistance to Pseudomonas syringae, Phytophthora, and Xanthomonas spp (de Toledo Thomazella et al., 2016). Climate change is making crops more susceptible to abiotic stress. The invention of CRISPR/Cas9 has accelerated the production of new varieties. Several developmental pathways that are mediated by brassinosteroids (BR) involve the brassinazole-resistant 1 gene (BZR1). The agrobacterium-mediated CRISPR-mediated mutation in BZR1 (engaged in a variety of brassinosteroid (BR)-mediated developmental processes) inhibited the induction of RESPIRATORY BURST OXIDASE HOMOLOG1 (RBOH1) and the production of H₂O₂. Exogenous H₂O₂ restored heat tolerance in tomato bzr1 mutants (Yin et al., 2018). To develop larger fruit size than the WT fruits, Cold Spring Harbor Laboratory edited the tomato CLAVATA-WUSCHEL (CLV-WUS) stem cell gene CLV3’s promoter region using the CRISPR/Cas9 technique (Li T. et al., 2018). High concentrations of steroidal glycoalkaloids (SGAs) give potato tubers a foul flavor and make them dangerous to consume. St16DOX (steroid 16-hydroxylase) was removed from the potato SGA biosynthetic pathway using CRISPR/Cas9, producing SGA-free potato lines (Nakayasu et al., 2018).

Ornamental plant production is linked with various features and markets like cut flowers and decorative vegetation, interior and exterior houseplants, window ledges, bulbous and nursery plants. In the scenario of ever-increasing demand, the floriculture industries require advancements and more different kinds with privileged qualities. The major objectives of ornamental breeding programs include establishing uniqueness in a blooming plant, color diversity, and perfumes, as well as inflorescence development by enhancing the flower count, altering the duration and longevity of flowering. Flower colors are the most impactful for their economic interest of any characteristic. Yellow cyclamens, red iris, blue chrysanthemums and roses, for example, are not found in nature due to the absence of pigment pathways (Tanaka et al., 2009). New decorative plant cultivars have been produced using a variety of breeding techniques. Apart from enhancing plant architecture and disease resistance, traditional plant breeding practices like crossbreeding and mutation breeding have been employed to produce various patterns and colours in plants. The majority of present methods for ornamental plants are extremely heterozygous, which produces a multifaceted transmission of genetic traits and polyploidy with several limits and drawbacks (Azadi et al., 2016; Sharma and Messar, 2017). Only a few countries allowed genetically modified (GM) ornamental plants commercially. For instance, the blue rose “ApplauseTM” and the violet carnation “MoondustTM,” both of which are genetically modified (GM) to hoard delphinidin-based anthocyanins, were developed and commercialized in the global flower market by the Japanese company SUNTORY and the Australian biotechnology company Florigene. However, consumers prefer genetically modified crops to genetically engineered ornamental plants (Nishihara and Nakatsuka, 2011). The first genome of an ornamental plant to undergo CRISPR/Cas9 modification was Petunia hybrida (Subburaj et al., 2016). The NITRATE REDUCTASE (PhNR) gene exhibited maximal targeted mutagenesis by direct administration of designed RNA-guided endonuclease (RGEN) ribonucleoproteins (RNPs) induced in Petunia protoplast cells. This has been made possible by the quick advancement of genome editing tools like ZFN, TALENs, and CRISPR/Cas9. These methods also enable a comprehensive understanding of the metabolic activity of annotated genes in newly sequenced and assembled genomes. Flower colour modification is now widely used in many plant species through genome-editing tools. Mutagenesis in the dihydroflavonol-4-reductase (DFR) gene of Ipomoea nilotica using CRISPR/Cas9 resulted in the first floral colour alteration in higher plants (Watanabe et al., 2017). Watanabe modified the carotenoid cleavage dioxygenase 4 (CCD4) gene using CRISPR/Cas9 to produce mutant Ipomoea plant. CRISPR/Cas9 approaches are used to target multiple MADS genes involved in floral organ development in the Phalaenopsis orchid (Tong et al., 2020). The chrysanthemum is one of the most well-known and important floricultural crops. Despite a complete genome sequence, due to the enormous genomic size and ploidy stages with a higher fraction of repetitive sequences, CRISPR/Cas systems will probably be challenging to implement. The CRISPR/Cas9 system functions in this plant, according to just one study (Kishi-Kaboshi et al., 2017) (Table.1).

The gradual increase in customer demand for extrinsic quality characteristics in fruits and vegetables, such as size, color, texture, aroma, storage life, etc., has been considered crucial. With increased public awareness, nutrition enhancement became economically significant. The commercialization of genetically engineered approved horticulture crops included virus-resistant papaya, squash variety, non-browning apple, fleshy pineapple, insect tolerant eggplant (BT brinjal), Brassica oleracea-(BolC.GA4. a gene), Tomato-(PSY1,Mlo,GABA-TP1,TP2, SIAGL6 gene), Potato- (StMB44, StALS1 gene) and Lactuca sativa-(BIN2 gene). The demand for parthenocarpic fruits and their socio-economic impacts accelerated the potential for developing genome editing. High-quality cultivars have been developed by silencing genes involved in signaling, knockout technique, reverse genetics, transgenesis, etc. The notable accomplishments through CRISPR/Cas9 techniques have brought about successful trait modification through mutation for enhancing nutritional gains. Mutations included loss of function in tomato (SIALC, SIFUL1, Pectate lyase), banana (MaLCY epsilon, MaPDS), apple (MdPDS, MdDIMP4), grapes, kiwi fruit (AcPDS, AcCENs), soybean (GmPRR3b, 37, GmFT2a), potato (StPPO), strawberry (FaTM6), gene or promoter insertion, cis-regulatory alleles in tomato (SICLV3, lycopene beta cyclase), citrus (CsLOBs) frame-shift mutation, gene replacement in tomato (SIALC), etc. The modifications in the aforesaid horticultural crops included increased flower and fruit size, fruit ripening, inflorescence branching, enhanced ascorbic acid synthesis, fortification of beta-carotene (banana), the transformation of perennial to annual (kiwi fruit), decreased tuber-browning and enhanced quality of berry (strawberry) (Tiwari et al., 2021). In an elegant research study, it has been published that the flavor of fruit directly modulates certain organic acids that influence organoleptic characteristics. Hence improving or minimizing them has a direct impact on the general character of a fruit (Sweetman et al., 2009). Acidity, which is quite a significant trait of the fruit harvest, has a direct impact on fruit quality. But it is especially critical for later processing. Hence, early-ripening apples often have high levels of acidity and low levels of sugar, which lowers the market demand for fresh consumption and leads to a low proportion of total organic acids to total carbohydrates. Numerous recent research in the fields of omics and quantitative trait loci (QTLs) (Xu et al., 2012) revealed a significant cellular synchronization between nutrition, post-harvest fruit quality, and shelf-life variation (Lin et al., 2016). The effectiveness of UV-C usage to combat the post-harvest impacts on early-ripened fruits produced at room temperature include ripening delay, senescence, preserving the significant ratio of fruit firmness, biosynthesis of flavonoids, phenolic content, enhanced antioxidant, and defense responsive molecules (Artés et al., 2009). The different doses for the UV irradiations have a marked positive impact by lowering the acidity-to-sugar ratio of various fruits and vegetables to preserve them post-harvest. UV-C treatment has been well-established on apples, mango, strawberry, peach, tomato, etc., promoting the flavour. The irradiations generate malate degradation-improving the quality of fruit, plant defense response mechanism against microbes, activating the gene regulation for disease resistance, enhancing salubrious phytochemical content, and regulating the proportions of antioxidant ratio on exposure to the shorter wavelength of UV-C. For successful implementation of post-harvest storage conditions to enhance nutritional benefits, the various horticultural produce effect is being noted. It includes the specific plant parts, developmental stages targeted for treatment, doses used, cultivar specificity, and harvesting time of the fruits and vegetables.

Postharvest loss and waste are becoming increasingly unsustainable as global horticulture crop production is inadequate for meeting human nutritional needs. Postharvest loss is unintentional. It outlines the sporadic losses that farmers occasionally sustain at the hands of consumer, including physical harm, internal bleeding, premature spoilage, and bug damage, among other things. Ornamental popularity has exploded recently, with an average worth of $16 billion in 2015 (Kader, 2004; Porat et al., 2018). Ornamental crops have a high moisture content, and the cold-chain process results in a loss of up to 50% of farm value (Pranuthi et al., 2018). Value decreases by 15% for each additional day spent on transit. Furthermore, the vase-life of ornaments is usually just 10–12 days after consumer purchase (Mamias, 2018). So, it is important to move things along a cold chain quickly. Reduced respiration rate is achieved by using cold temperatures, which also increases shelf life. As vegetables and fruits travel from farmer to customer, various factors (processing, storage, and transportation conditions) contribute to such a deteriorative process. Understanding where food supply chain losses occur is critical for determining possible causes and improving best post-harvest practices (Gustavsson et al., 2011). Temperature, moisture content, level of ethylene hormone, and the storage proportion of O₂ to CO₂ must be managed to ensure yield shelf-life and quality (Kader, 2004). Infectious agent’s invasion attempts on harvested products are likely to caramelise the fruit ingredients, resulting in diseased or spore-covered fruits and their metabolic by-products. The products are unaesthetic and non-edible due to the acidic, bitter, foul-smelling, and toxicants produced (Encinas-Basurto et al., 2017).

Fruits that are overripe or underripe are more vulnerable to physiological disorders. Sometimes entire products are discarded as they are unsafe to eat (ömer AZABAĞAOĞLU, 2018). Incorrect cultural practises such as cold snaps, weather, water stress, heavy rainfalls, pathogens, physiological disorders, plant health, safeguards, water management, fertilization, and cutting possibly cause fruit and vegetable damage during the preharvest period. Harvesting period loss (4%–12%) is due to inaccurate harvesting time estimation, harvesting at the wrong time, inappropriate harvesting procedures implementation, and not applying pre-cooling to fruits such as cherries during the harvesting process (Özdemir et al., 2003). According to the International Refrigeration Institute (IIR), 23% of food waste in developing countries is generated when cooling systems are not used [(Dupont et al., 2009), 2009]. Constant cold storage ensures that the product reaches the consumer in pristine condition. The lack of adequate storage facilities is the leading cause of the degradation of both qualitative and quantitative factors of food production from food harvest to consumption level in underdeveloped countries (Tatlıdil et al., 2013). Fresh produce changes cannot be avoided, but they can be reduced with preventative measures, including cold temperature, relative humidity, appropriate transportation and packaging, and others (Ahmad and Siddiqui, 2015). The most popular ornamental plants, such as roses, liliums, lisianthus, chrysanthemums, and carnations, demonstrated varying levels of ethylene sensitivity and flower longevity. The use of breeding methods in conjunction with ethylene screening was only partially successful. It is possible to expand the life of ornamental plants by using molecular techniques (Netam, 2018). Gene-editing of 1-aminocyclopropane-1-carboxylate oxidase1 (PhACO1) gene which encodes for ethylene producing enzyme via CRISPR/Cas9 method resulted in decreased ethylene and delayed petal senescence in the petunia cultivar “Mirage Rose” (Xu et al., 2020). Mutations in the EPHEMERAL1 (EPH1) gene, which encodes the major regulator for petal senescence as a NAC transcription factor, resulted in delayed petal senescence in Japanese morning glory (Ipomoea nil “Violet”) plants (Shibuya et al., 2018). MaACO1 mutated through CRISPR/Cas9 system produced less ethylene and had a longer shelf life in the ripening stage (Hu et al., 2021). To date, the CRISPR/Cas9 gene-editing approach has already been effectively implemented in many fruit crop species, such as climacteric ripening species, like apples (Malnoy et al., 2016b; Nishitani et al., 2016), bananas (Kaur et al., 2018), kiwifruit (Wang Z. et al., 2018)), and non-climacteric ripening species, such as sweet orange (Jia and Wang, 2014), Duncan grapefruit (Jia et al., 2016), grapevine (Malnoy et al., 2016b), watermelon (Tian et al., 2017), cucumber (Chandrasekaran et al., 2016), and cultivated strawberries (Martín-Pizarro et al., 2019).

Abiotic stress, which includes dehydration, soil salinity, and high heat, poses serious risks to crop development, yield, and quality (Sharma and Gayen, 2021). The effect of adverse conditions on the plant is more common in tropical regions than temperate regions. High temperature creates more threat in tropical countries. Drought stress is another abiotic stress limiting crop development and production, which is continuously increasing due to global warming. Crop yields are becoming more and more susceptible due to unfavorable climate changes, deteriorating soil health, and declining air quality. Researchers are attempting to create a transgenic crop that can produce more and easily tolerate severe and variable conditions. CRISPR/Cas9 technology has been implemented to increase crop yield. Abiotic stress, such as drought, soil salinity, and high temperature, create major problems for the growth and development of the crop, drastically lowering agricultural production and quality. Resistance to the abiotic stress created by the many genes is a complex trait. With the use of nucleases that cause double-strand breaks by providing a new method for editing genes in molecular biology, which transformed the field of genome editing. ZFNs are credited as the 1st genome editing technique that used programmable nucleases to make a significant advancement in the field of genome engineering (Chandrasegaran and Carroll, 2016). After a while, TALENs (Transcription activator-like effector nucleases), which are entirely dependent on TALEs of the bacteria, additionally broaden genome engineering potential. TALENs were quickly adapted to approximately 40 different types of species for genome editing (Chandrasegaran and Carroll, 2016). Scientists worldwide have turned their attention to the CRISPR/Cas9 technologies since their discovery because of their numerous advantages over TALENs and ZFN (Mao et al., 2013). Unlike the previous technology, TALENs and ZFN, which use a protein motif to identify the target, CRISPR/Cas9 is based on RNA-DNA recognition to generate the double-strand break. Apart from this, there are many benefits of the CRISPR/Cas9 technology over the TALENs, and ZFN 1) Ease of the target design 2) ability to directly inject RNAs encoding the Cas9 protein and gRNA (guide RNA) to cause mutation, and 3) create targeted mutations in numerous genes in a single event because to the simplicity of multiplexing (Ma et al., 2015; Malzahn et al., 2017). A new genetic engineering tool is precise genome editing for crop improvement. Multiple techniques such as TALENs (Christian et al., 2010; Li et al., 2011; Miller et al., 2011), ZFNs (Maeder et al., 2008; Sander et al., 2011), RGENs (RNA-guided nucleases), and CRISPR/Cas9 (Jinek et al., 2012; Cong et al., 2013; Mali et al., 2013), all these types of technology developed for the targeted genome editing. CRISPR/Cas9 technology-based genome editing in the crop can be used to modify almost any sequence to show its function in the organism’s genome. CRISPR/Cas9 generated SIMAPK3 participates in tomato dehydration resistance by preventing oxidative damage to the cell wall generated by stress, further adjusting the transcription of genes linked to drought stress (Wang et al., 2017). Recently, CRISPR/Cas9-generated genome engineering for high-temperature resistance has been achieved by focusing on an S gene, SIAGL6 (SIGAMOUS-LIKE 6), in S. lycopersicum, which has a significant role in the improvement in fruit quality against high-temperature stress (Klap et al., 2017). In tomatoes involvement of the auxin in salinity stress and osmotic stress resistance and the role of the ARF4 (auxin response factor 4) providing the resistance and confirm the use of the CRISPR/Cas9 tools to develop tolerant plants (Bouzroud et al., 2020). In tomato genome editing by the CRISPR/Cas9 tools under the abiotic stress in various genes such as SIMAPK3 (Kong et al., 2012), SILOX, SIGST, SIDREB (Wang et al., 2017), SILBD40 (Liu et al., 2020), SINPR1 (Li et al., 2019), and SIMAPK6 (Li et al., 2021), under the abiotic stress condition. CRISPR/Cas tools were used to generate mutation in lettuce plants to understand better the mechanism of NCED4 (Bertier et al., 2018). During heat stress, CRISPR/Cas9 technology was used for silencing SIMAPK3 in tomatoes (Yu et al., 2019). This technique is used to increase the expression level of the ARGOS8 gene (a negative regulator of the ethylene response) to develop drought resistance maize crops, and the ARGOS8 gene promoter changed into GOS2. These traits had a major role in the enhancement of grain yields during drought stress conditions (Hirai et al., 2007). Overexpression of the biosynthesis of the melatonin gene in plants was identified as an abiotic stress resistance (Byeon and Back, 2016; Antoniou et al., 2017). Currently, the CRISPR/Cas9 genome engineering technique further expands the application of these tools to genome-wide screening for the improvement of the desired trait (Rodríguez-Leal et al., 2017; Mahas and Mahfouz, 2018). Gain- or loss-of-function mutants can result from precise base alterations made by the CRISPR/Cas9 system at desired gene locations. There is no doubt that CRISPR/Cas technology might replace conventional crop breeding methods. It depends on locating plant populations with genetic differences to produce desired features in crop cultivars.

The gRNA sequencing method can be used to identify novel allelic variations that match a specific desirable trait that could be introduced into plant populations by this base editing technique (Eid et al., 2018).

Biotic stress, such as insects, viruses, fungi, and bacteria, can attack plants and cause severe damage (Langner et al., 2018). CRISPR/Cas9 tools have been developed to obtain disease-tolerant plants (Arora and Narula, 2017). CRISPR/Cas technology is a beneficial method for creating stable transgenic lines. Following the development of CRISPR/Cas technology against bacterial, viral, and fungal infections, which result in significant losses in plants. Despite the information of technological advances being already reported in CRISPR/Cas9 technology for the fruits, vegetables, and ornamental plant improvement, not much more progress has been made towards the uses of CRISPR/Cas9 genome engineering tool for biotic stress resistance in fruits, vegetables, and ornamental crops. The response of the plants toward biotic stress is more complicated; during the biotic stress circumstances, several crucial genes are overexpressed and down-expressed.

For the inactivation of the DMR6 ortholog in Solanum Lycopersicum, researchers used the CRISPR/Cas9 system. They discovered that mutations in the dmr6 gene exhibit disease tolerance against various pathogens, including species Xanthomonas, Phytophthora capsica, and P. syringae, without causing any discernible adverse effects (de Toledo Thomazella et al., 2016). It has been demonstrated that tomato MAPK3 (mitogen-activated protein kinase-3) gains the potential to Botrytis cinerea (Zhang S. et al., 2018). Scientists used CRISPR/Cas9 to develop Solanum Lycopersicum JAZ2 (Jasmonatezim domain protein 2) repressors lacking C-terminal jasmonate associated domain (JAZ2Δjas). These repressors provide tolerance against the P. syringae, indicating CRISPR/Cas9 technology for the development of resistance fruit and its implementation in agriculture (Ortigosa et al., 2019). In Vitis vinifera, knockout of the WRKY5 by the CRISPR/Cas9 technology encoding a TF that has a significant role in biotic stress response, WRKY5 exhibits disease tolerance against B. cinerea (Wang X. et al., 2018). The CRISPR/Cas9 technology is crucial for the fruits such as apples (Malus domestica) and grapes (Vitis vinifera), which have long life cycles and generation times. Numerous papers have described the use of CRISPR/Cas9 so far with fruits like Citrus reticulate (Jia and Wang, 2014), grapes (Malnoy et al., 2016a; Ren et al., 2016; Wang et al., 2016), apples (Malnoy et al., 2016a; Nishitani et al., 2016), Solanum tuberosum (potato) (Andersson et al., 2017), banana (Musa balbisiana) (Tripathi et al., 2019), cucumber (Chandrasekaran et al., 2016), papaya (Gumtow et al., 2018), citrus (Jia et al., 2016; Peng et al., 2017). The fruits, vegetables, and ornamental plant production and growth are exposed to continuously increased risks of biotic stress. The CRISPR/Cas9 technology is used in applications to obtain new germplasm resources rapidly. As fruits, vegetables, and ornamental plants are sensitive to biotic stress, it can make achieving optimal yield difficult, emphasizing the significance of creating stress-resistant crops.