Biotechnological Advances in Mango (Mangifera Indica L.) and Their Future Implication in Crop Improvement — a Review ⁎ Hare Krishna , S.K
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Biotechnology Advances 25 (2007) 223–243 www.elsevier.com/locate/biotechadv Research review paper Biotechnological advances in mango (Mangifera indica L.) and their future implication in crop improvement — A review ⁎ Hare Krishna , S.K. Singh Division of Fruits and Horticultural Technology, Indian Agricultural Research Institute, New Delhi-110 012, India Received 21 September 2006; received in revised form 2 January 2007; accepted 7 January 2007 Available online 17 January 2007 Abstract Biotechnology can complement conventional breeding and expedite the mango improvement programmes. Studies involving in vitro culture and selection, micropropagation, embryo rescue, genetic transformation, marker-assisted characterization and DNA fingerprinting, etc. are underway at different centers worldwide. In vitro culture and somatic embryogenesis of several different genotypes have been achieved. The nucellus excised from immature fruitlets is the appropriate explant for induction of em- bryogenic cultures. High frequency somatic embryogenesis has been achieved in some genotypes; however, some abnormalities can occur during somatic embryo germination. Embryo rescue from young and dropped fruitlets can improve the hybridization success in a limited flowering season. Protocols for protoplast culture and regeneration have also been developed. In vitro selections for antibiotic tolerance and fungal toxin resistance have been very promising for germplasm screening. Genetic transformation using Agrobacterium tumefaciens has been reported. Genes that are involved with fruit ripening have been cloned and there have been attempts to deliver these genes into plants. DNA fingerprinting and studies on genetic diversity of mango cultivars and Mangifera species are also being conducted at several research stations. The purpose of this review is to focus upon contemporary information on biotechnological advances made in mango. It also describes some ways of overcoming the problems encountered during in vitro propagation of mango. © 2007 Elsevier Inc. All rights reserved. Keywords: Mango; Biotechnology; In vitro; Recalcitrance; Somatic embryogenesis; Genetic transformation; Somaclonal variations Contents 1. Introduction ...................................................... 224 2. Problemsassociatedwithmangomicropropagation................................... 225 2.1. Phenol exudation, media browning and explant necrosis ............................ 225 2.2. Latent systemic contamination ......................................... 225 2.3. In vitro recalcitrance .............................................. 226 3. In vitro propagation .................................................. 226 3.1. Somatic embryogenesis ............................................. 226 3.1.1. Induction of embryogenic cultures ................................... 228 ⁎ Corresponding author. Present address. Central Institute of Temperate Horticulture — Regional Station, Mukteshwar-263 138, U.A., India. E-mail address: [email protected] (H. Krishna). 0734-9750/$ - see front matter © 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.biotechadv.2007.01.001 224 H. Krishna, S.K. Singh / Biotechnology Advances 25 (2007) 223–243 3.1.2. Maintenance of embryogenic cultures ................................ 229 3.1.3. Maturation of somatic embryos.................................... 230 3.1.4. Germination and conversion into normal plantlets ........................... 231 3.2. Organogenesis ................................................. 232 3.3. Embryo culture ................................................ 233 4. Somaclonal variation/in vitro selection ........................................ 233 5. Molecular biology................................................... 234 5.1. Identification of cultivars ........................................... 234 5.2. DNA markers ................................................. 236 5.2.1. Variable number tandem repeat sequence (VNTRS) .......................... 236 5.2.2. Single sequence repeats (SSRs).................................... 236 5.2.3. Amplified fragment length polymorphism (AFLP) .......................... 237 5.2.4. RAPD and RFLP markers ...................................... 237 5.2.5. Inter-Simple-Sequence-Repeats (ISSR) ................................ 238 6. Cloning of useful gene(s) ............................................... 238 7. Genetic transformation ................................................ 239 8. In vitro germplasm conservation ........................................... 239 9. Conclusion and future thrusts ............................................. 239 References ......................................................... 240 1. Introduction in bearing, dwarfing, regularity in bearing with high yield, resistant to diseases, pests and physiological dis- The mango (Mangifera indica L.) is one of the orders and good keeping quality. In addition, the world choicest fruit crops of tropical and sub-tropical regions mango trade is narrowed to a great extent owing to the of the world, especially in Asia. Its popularity and rapid perishable nature of fruits (Lizada, 1993). Mango is importance can easily be realized by the fact that it is a climacteric fruit and long distance transport is some- often referred as ‘King of fruits’ in the tropical world times a problem. Anthracnose caused by Colletotrichum (Singh, 1996). sp. is regarded as one of the single most significant Globally, there are a number of problems that affect production and post-harvest problem (Dodd et al., 1998). mango production. Being highly cross-pollinated and There is a long-felt need to develop a variety possessing owing to the fact that most of superior clones of mango most of the desirable horticultural attributes. Earlier, including ‘Indian’ and ‘Floridan’ cultivars are mono- Singh (1996) suggested that an ideal mango variety embryonic, propagation through sexual means does not should be dwarf, regular bearer with medium size fruit ensure true-to-the type plant reproduction. This leads to (250–300 g). Additionally, it should be highly tolerant of long juvenile phase of such plants. Production problems various fungal and bacterial diseases. The fruits should are associated with both scion and rootstock. Scion have stable pleasant flavour combined with good keep- cultivar problems include biennial bearing habit, large ing quality. The need for such an ideal phenotype can not tree size, susceptibility to major diseases and pests, be met by conventional breeding. Conventional breeding short-post-harvest life and disorders like, malformation, of woody perennial fruit crops like mango is difficult spongy tissue, etc. (Iyer and Degani, 1997). For root- owing to long juvenile phase, self incompatibility, low stock breeding, Iyer and Degani (1997) suggested that fruit set, high fruit drop, single seed per fruit, high degree the priority should include tolerance of various soil of cross-pollination, polyembryony, polyploidy and related stresses, induction of dwarfing and high degree of heterozygous nature, meager information on inheritance polyembryony to ease rapid multiplication, i.e. clonal of important quantitative traits, etc. Inclusion of bio- plants etc. Barring some hybrids, almost all the popular technology in a breeding programme would expedite the cultivated varieties are chance seedlings resulting from development of desired cultivar(s). Employing biotech- natural cross-pollination. Some hybrids are gaining nology to correct genetic flaws of existing varieties has ground owing to their novel characteristic features; great potential importance. however, there is an acute shortage of this material. Most Micropropagation of mango has not met with the of the important varieties are not amenable to hi-tech commercial success as obtained in other fruit crops like cultivation practices and do not meet the requirements of pineapple, banana and strawberry. This is due to many modern horticultural production systems like precocity problems associated with it, viz., latent microbial H. Krishna, S.K. Singh / Biotechnology Advances 25 (2007) 223–243 225 infection, excessive polyphenol exudation, early explant round the year unlike the explants provided by the necrosis, etc. Biotechnology could resolve some of the immature fruitlets only during certain parts of the year. most serious problems of the mango industry. Moreover, But high phenolic exudation owing to activation of molecular methods are useful for taxonomical character- oxidative enzyme system during the excision of plants, ization, to understand the regulation and expression of explants browning, deep seated contamination, medium important traits/genes, etc. The attempted and potential discolouration and slow in vitro growth response have biotechnological interventions are depicted in Fig. 1. made it an ordeal for workers dealing with this crop. In order to reduce phenolic exudation during in vitro cul- 2. Problems associated with mango micropropagation ture, Raghuvanshi and Srivastava (1995) suggested pretreatment of leaf explants using liquid shaker culture. A successful in vitro culture initiation is a prerequi- Explants kept in liquid MS medium supplemented with site for micropropagation, since failure at this very stage 1% PVP followed by inoculation on gelled MS medium. leaves a tissue culturist in a predicament, where no Later, Chavan et al. (2000) also suggested dipping prospect of redeeming is in sight. apical and axillary buds in 0.5% polyvinylpyrolidine Preliminary