Micropropagation in litchi: concept, constraints and recent advances – a review

Abstract

Owing to the genetically diverse nature of seedlings produced, seed propagation in litchi is not advisable. Furthermore, the long juvenile phase of seed propagated plants accompanied with the tendency of irregular bearing makes this method of propagation uneconomical and inefficient. Conventionally litchi is propagated by vegetative means like air layering, which again are slow and inefficacious. Hence use of micropropagation for large scale production of litchi plants can prove to be a more potent alternative. Albeit, till date only marginal success could have been achieved in in vitro regeneration of litchi, various studies have shown that micropropagation indeed can be used in litchi with varied rate of success. In past few years, encouraging results have been reported in regenerating plantlets from callus culture derived from young leaf explants on MS media. Some studies have shown production of multiple shoots by using nodal explants of 3-4 year old litchi on woody plant medium. Embryo culture in litchi has reportedly been successful by utilizing immature embryos of different sizes and age in a range of different media and achieving multiplication through induction of adventitious buds from embryonic shoots. Multiple shoots have also been obtained by direct germination of litchi seeds in liquid MS media. Attempts involving induction of somatic embryogenesis in cultures of zygotic embryos of litchi and anther culture have also been reported. Like other woody perennials secretion of polyphenols is also a major constraint in litchi micropropagation. In order to combat this problem, antioxidants like ascorbic and citric acids, in the growth media have been used by some workers with varied degrees of efficacies. Another serious problem affecting the success of micropropagation in litchi is the fungal infection, to inhibit the growth of which use of Bavistin and elimination of organic nutrients from growth medium have been tried. In this communication, we aim to critically analyze the major issues that are restraining the use of micropropagation in litchi along with the recent advances made in this field and also to investigate its future implications.