Table 2.
Transgenic horticultural crops for abiotic stress tolerance/management
| S. no. | Crop species/cultivar | Gene and genetic transformation method used | Mechanism of action | Target trait | Trait improvement | References |
|---|---|---|---|---|---|---|
| (A) Drought tolerance | ||||||
| 1. | Apple | Osmyb4; Agrobacterium tumefaciens-mediated gene transfer | A Myb family transcription factor, leads to accumulation of various solutes compatible to abiotic stress tolerance | Drought and cold tolerance | Enhanced tolerance to drought and low temperature stress in transgenic plants | Pasquali et al. (2008) |
| MdC1PK61; Agrobacterium tumefaciens-mediated gene transfer | Synthesizes a CBL-interacting protein kinase (C1PK) | Salt, drought and chilling tolerance | Enhanced tolerance to drought and low temperature and salt stress in transgenic plants | Wang et al. (2012) | ||
| 2. | Banana | MusaWRKY71; Agrobacterium tumefaciens-mediated gene transfer | Encodes a WRKY transcription factor | Multiple abiotic stress tolerance | Enhanced tolerance to drought, salinity and high temperature | Shekhawat and Ganapathi (2013) |
| MusaSAP1; Agrobacterium tumefaciens-mediated gene transfer | Encodes for stress associated proteins (SAPs) | Multiple abiotic stress tolerance | Enhanced tolerance to drought, salinity and high temperature | Sreedharan et al. (2012) | ||
| 3. | Citrus | P5CS gene; Agrobacterium tumefaciens-mediated gene transfer | Encodes for the biosynthesis of proline | Drought tolerance | Enhanced tolerance to drought and low temperature stress in transgenic plants | De Carvalho et al. (2013) |
| P5CSF129A; Agrobacterium tumefaciens-mediated gene transfer | Provides protection against reactive oxygen species(ROS) by altering enzymes activity | Drought tolerance | Enhanced tolerance to drought and low temperature stress in transgenic plants | De Campos et al. (2011) | ||
| 4. | Strawberry | Osmotin; Agrobacterium tumefaciens-mediated gene transfer | Increase the level of proline accumulation | Salinity tolerance | Enhanced tolerance to salinity stress in transgenic plants | Husaini and Abdin (2008) |
| 5. | Mulberry cv. K2 | Osmotin; Agrobacterium tumefaciens-mediated gene transfer | Increase the level of proline accumulation | Salinity and drought tolerance | Enhanced tolerance to drought and salinity stress in transgenic plants | Das et al. (2011) |
| 6. | Chrysanthemum (Chrysanthemum morifolium) cv. ‘Jinba’ | CmWRKY1 transcription factor (derived from C. morifolium); Agrobacterium tumefaciens-mediated gene transfer | CmWRKY1 works as positive regulator in drought stress | Drought stress tolerance | The transgenic plants displayed increased drought tolerance in PEG stress as compared to control plants | Fan et al. (2016) |
| 7. | Tomato (Solanum lycopersicum cv. Aika Craig) | Sly-miR169c, an miR169 family member; Agrobacterium tumefaciens-mediated gene transfer | Down regulates the transcripts of target genes namely; three nuclear factor Y subunit genes (S1NF-YA1/2/3) and one multidrug resistance-associated protein (slMRP1) gene | Drought tolerance | Transgenic plants exhibited reduced stomatal opening, decreased transpiration rate, lowered leaf water loss and enhanced drought tolerance | Zhang et al. (2011a, 2011b) |
| 8. | Potato cv. Superior | Cod A gene (from Arthrobacter globiformis); Agrobacterium tumefaciens-mediated gene transfer | Cod A gene codes for glycine betaine, which scavenges oxidative stress-inducing molecule (free radicals) and it also protects the photosynthetic system in plants | Drought tolerance | The transgenic potato plants displayed a stronger antioxidant activity, higher chlorophyll content, more efficient photosynthesis and better recovery, comparatively | Cheng et al. (2013) |
| 9. | China rose (Rosa chinensis) | RcXET and MtDREBIC genes; Agrobacterium tumefaciens-mediated gene transfer | XET and DREBIC genes are up-regulated in response to various abiotic stresses and imparts tolerance to the plant cells | Freezing and drought tolerance | Increased EC%, proline content, soluble sugar, photosynthesis rate, negative water potential and turgor loss point in transgenic plants leading to a better tolerance towards drought and freezing | Chen et al. (2016) |
| (B) Heat tolerance | ||||||
| 1. | Tomato (Solanum lycopersicum) | Yeast SAMDC gene; Agrobacterium tumefaciens-mediated gene transfer | SAMDC (S-adenosyl-methionine decarboxylase) is one of the key enzymes involved in the biosynthesis of polyamines, which protect the plants against heat stress | Heat stress | Transgenic plants produced 1.7–2.4 times, higher level of spermidine and spermine than the wild-type plants and expressed tolerance to heat stress with enhanced antioxidant enzyme activity and protection of membrane lipid peroxidation | Cheng et al. (2009) |
| Tomato cv. Zhongshu No. 5 | cAPX gene; Agrobacterium tumefaciens-mediated gene transfer | APX encodes for antioxidant enzyme which removes H2O2, a reactive oxygen species (ROS) produced under heat stress | UV-B and heat stress tolerance | Transgenic plants and fruits expressed enhanced tolerance to heat (40 °C) and UV-B stress as compared to wild-type plants | Wang et al. (2006) | |
| 2. | Chrysanthemum morifolium cv. ‘Zhongshanzigui’ | CgHSP70 gene (from C. morifolium); Agrobacterium tumefaciens-mediated gene transfer | HSPs function as molecular chaperons, which are involved in correct protein folding, assembly, translocation, degradation and they also provide stability to integral proteins and cell membranes under heat stress | Heat tolerance | The transgenic lines exhibited an increased peroxidase (POD) activity, higher proline content and reduced malondialdehyde (MDA) content and were better able to tolerate heat stress than wild-type plants | Song et al. (2014) |
| 3. | Potato (Solanum tuberosum) cv. Desiree | StnsLTP1 gene (from potato); Agrobacterium tumefaciens-mediated gene transfer | StnsLTPI gene imparts tolerance to various abiotic stresses as a result of enhanced activation of antioxidative defense mechanisms via cyclic scavenging of reactive oxygen species (ROS) and co-coordinating the expression of stress related genes | Heat, drought and salinity tolerance | Transgenic potato lines displayed enhanced cell membrane integrity and an increased level of antioxidant enzyme activity with enhanced accumulation of ascorbates and upregulation of various stress related genes including StAPX, StCAT, StSOD etc. under stress conditions | Gangadhar et al. (2016) |
| Potato | Cu/Zn SOD (from Manihot esculenta); Agrobacterium tumefaciens-mediated gene transfer | ROS scavenging enzyme and thus helps in quenching of free radicals released under heat stress in plants | Heat stress | Transgenic plant expressed enhanced tolerance to 250 μM methyl viologen and reduced visible damage due to heat stress | Tang et al. (2006) | |
| (C) Salinity tolerance | ||||||
| 1. | Apple | MdNHX1 gene; Agrobacterium tumefaciens-mediated gene transfer | Acts as Na+/H+ antiporter | Salinity tolerance | Enhanced tolerance to salinity stress in transgenic plants | Li et al. (2010) |
| 2. | Banana | MusaDHN-I gene; Agrobacterium tumefaciens-mediated gene transfer | Over-expression of dehydrin gene and a LEA protein | Drought and salinity | Enhanced tolerance to drought and salinity stress | Shekhawat et al. (2011) |
| 3. | Kiwi | AtNHX1 gene; Agrobacterium tumefaciens-mediated gene transfer | Keeps K+/Na+ ratio high during salinity stress conditions | Salinity | Enhanced tolerance to salinity stress in transgenic plants | Tian et al. (2011) |
| 4. | Pear | SAMDC2 gene; Agrobacterium tumefaciens-mediated gene transfer | Encodes for the biosynthesis of polyamines | Salinity | Enhanced tolerance to salinity stress in transgenic plants | He et al. (2013) |
| Pear | SPDS gene; Agrobacterium tumefaciens-mediated gene transfer | Encodes for the biosynthesis of polyamines | Salinity | Enhanced tolerance to salinity stress in transgenic plants | Wen et al. (2010) | |
| 5. | Tomato (Solanum lycopersicum) cv. Zhongshu No. 5 | cAPX gene; Agrobacterium tumefaciens-mediated gene transfer | Ascorbate peroxidase plays a key role in quenching hydrogen peroxide (H2O2) in plant cells, thus providing protection against oxidative injury induced by chilling and salt stress | Chilling and salinity | The transgenic plants showed better seed germination rate (26–37%) than the wild type (3%) when the seeds were placed at 9 °C for 5 weeks and higher APX activity under salinity stress (200–250 mM) conditions | Wang et al. (2005) |
| Cherry tomato—C, H and F lines | GalUR gene (D-galacturonic acid reductase gene), derived from strawberry; Agrobacterium tumefaciens-mediated gene transfer | GalUR gene codes for higher level of ascorbic acid biosynthesis, which imparts tolerance to salinity stress | Salinity stress | Transgenic tomato plants were found more tolerant to abiotic stress-induced viologen, Nacl and mannitol and with higher expression levels of APX and CAT, responsible for imparting additional capabilities for salt tolerance | Lim et al. (2016) | |
| Tomato | Na+/H+ antiporter gene (TaNHX2) from wheat; Agrobacterium tumefaciens-mediated gene transfer | TaNHX2 gene leads to the production of osmolytes to maintain the cell membrane stability | Salinity tolerance | Better salinity tolerance in transgenic plants comparatively | Yarra et al. (2012) | |
| 6. | Citrus (Carrizo citrange root stock) | Yeast HAL2 gene; Agrobacterium tumefaciens-mediated gene transfer | HAL-2 gene is involved in the pathway of methionine biosynthesis and confers tolerance to Lithium and Sodium. | Salinity tolerance | Transgenic plants showed better tolerance to salt stress than non-transgenic plants | Cervera et al. (2000) |
| 7. | Sweet potato (Ipomoea batatas) cv. Sushu-2 | SoBADH (Spinacia oleracea derived betaine aldehyde dehydrogenase gene); Agrobacterium tumefaciens-mediated gene transfer | Glycine betaine protects the plant cells from abiotic stress by providing protection against cell damage by maintaining cell membrane integrity, stronger photosynthetic activity, reduced ROS production and activation of ROS scavenging mechanism | Salinity, oxidative stress and chilling/cold stress | The transgenic plants improved tolerance towards salinity, oxidative stress and low temperature | Fan et al. (2012) |
| 8. | Chilli pepper (Capsicum annum L.) cv. Aiswarya 2103 | Osmotin gene; Agrobacterium tumefaciens-mediated gene transfer | Over-expression of osmotin gene induces biosynthesis of proline and confers tolerance to osmotic stress | Salinity tolerance | Transgenic pepper plants could survive salinity level up to 300 mM Nacl concentration | Subramanyam et al. (2011) |
| Chilli pepper cv. Q4 | Na+/H+ antiporter gene (TaNHX2) from wheat; Agrobacterium tumefaciens-mediated gene transfer | TaNHX2 gene leads to the production of osmolytes to maintain the cell membrane stability | Salinity tolerance | Transgenic lines revealed enhanced levels of proline, chlorophyll, superoxide dismutase, ascorbate peroxidase, relative water content and reduced level of H2O2 and malondialdehyde as compared to the non-transformed plants under salt stress conditions | Bulle et al. (2016) | |
| 9. | China rose (Rosa chinensis) | AtDREB2A-CA gene; Agrobacterium tumefaciens-mediated gene transfer | Over-expression of AtDREB2A-CA gene enhances salinity stress tolerance in Chinese rose by altering the leaf ultra structure in response to salt stress | Salinity stress | Enhanced salinity tolerance in transgenic plants | Josine et al. (2015) |
| 10. | Chrysanthemum morifolium | CmWRKY17 transcription factor; Agrobacterium tumefaciens-mediated gene transfer | WRKY transcription factors work sometime as positive and sometime as negative regulators in a variety of abiotic stress responses in plants | Salinity stress | Over-expression of CmWRKY17 TF in chrysanthemum increased plants sensitivity to salinity stress | Li et al. (2015) |
| 11. | Mulberry (Morus indica) cv. K-2 | HvaI gene (from barley); Agrobacterium tumefaciens-mediated gene transfer | LEA proteins (encoded by HvaI gene) protect cells against abiotic stresses by sequestering ions, stabilization of macro molecules and membranes, and act as antioxidants | Salinity, drought and cold tolerance | The transgenic lines displayed an enhanced level of tolerance to drought, salinity and cold conditions than normal plants as quantified by free proline, membrane stability index (MSI) and PSII activity | Checker et al. (2012) |
| 12. | Bottle gourd line ‘G5′ | AVP1 gene derived from Arabidopsis thaliana; Agrobacterium tumefaciens-mediated gene transfer | AVP1 gene is involved in imparting salt tolerance | Salinity tolerance | The transgenic lines exhibited an improved salt tolerance and maintained higher relative water content under salt stress regime in glasshouse | Han et al. (2015) |
| (D) Herbicide tolerance | ||||||
| 1. | Petunia hybrida | EPSP synthase gene; Agrobacterium tumefaciens-mediated gene transfer | Over-production of the enzyme renders inhibition by glyphosate ineffective | Glyphosate tolerance | Transformed petunia cells as well as regenerated transgenic plants were found tolerant to glyphosate | Shah et al. (1986) |
| 2. | Pineapple | Bar gene; Particle bombardment -mediated gene transfer | Bar gene codes for enzyme PAT, which acetylates bialaphos rendering it inactive | Bialaphos resistance/tolerance | Transgenic plants were found tolerant to 1600 ml/rai of the herbicide Basta® X (stock concentration 15% w/v glufosinate ammonium), this being twice the dose recommended for field application of the herbicide | Sripaoraya et al. (2006) |
| 3. | Potato | Bar gene; Agrobacterium tumefaciens-mediated gene transfer | Bar gene codes for enzyme PAT, which acetylates bialaphos rendering it inactive | Bialaphos resistance/tolerance | Transgenic potato expresses tolerance to bialaphos | Khan et al. (2008) |