A comprehensive review on the in vitro culture techniques adopted for the genus Phyllanthus

Phyllanthus species have been shown to produce around 500 different secondary metabolites. This has led to wide spread research on increasing production of Phyllanthus species by both traditional breeding methods as well as biotechnological approaches. Due to the geographic, climatic and seasonal influences on Phyllanthus growth, a controlled environment available in tissue culture methods might be the best strategy to enhance supply of the lignans. This approach may also pave the way to preserve species diversity, for mass cultivation in limited space and time, and increase the production of phytochemicals by varying nutrients, photoperiods, temperature, plant growth regulators (PGRs), precursors and elicitors. This review compiles all the attempts carried out till date on the in vitro propagation of different Phyllanthus species known to produce lignans. Types of explants, sterilizing agents, micro and macronutrients, vitamins, plant growth regulators, precursors and elicitors (includes biotic and abiotic), acclimatization rates and their yields are discussed here in order to provide a succinct and useful summary. In spite of the extensive work carried out, an optimized protocol for the in vitro culture of Phyllanthus species is not available. The progress made in various aspects of tissue culture such as tissue/organ culture, micropropagation, organogenesis, synthetic seeds, cell suspension culture, hairy root culture are also reviewed in detail. However, only seven species of the genus have been explored for in vitro cultures. Even though multiple studies have been carried out on in vitro cultures techniques of all the Phyllanthus species, secondary metabolite production is not properly documented or reported. Among the seven, maximum research is focussed on P. amarus. An urgent need has arisen to explore the micropropagation of other species in this genus as well as to assess the levels of secondary metabolite production in them.