Recent Advances of Biotechnological Tools on Diverse Species of Citrus: Current Applications and Future Prospects

Based on the long term conservation of several endangered and indigenous species of Citrus, significant impact of biotechnological tools particularly in terms of in-vitro micropropagation methods in addition to synthetic seed production using encapsulation of plant propagules including shoot tips, nodal segments, androgenic embryos, embryogenic callus, etc. in sodium alginate has been highlighted in this manuscript. When seed is not available in enough quantity for raising seedlings for rootstock or have low levels of polyembryony and do not produce adequate quantities of nucellar seedlings, then micropropagation techniques could quickly supply in vitro regenerated rootstock or budwood. Rapid, mass-production and cost-effective biotechnological tools for propagation of citrus rootstocks and budwood would be of great importance in this regard. Reports on another aspect of long term conservation particularly based on storage of cells, tissues and organs of drought tolerant species of Citrus at ultra-low temperature preferably at -196 ºC via applications of cryopreservation techniques using vitrification and encapsulation or dehydration methods has been highlighted in this manuscript. In addition, several research on techniques of in-vitro micrografting using superior scion and rootstocks of two different species of Citrus with an objective of eradication of virus infected citrus stocks for successful production of grafts have been reviewed. Furthermore, effects of explants either through direct and indirect regeneration and conversion into a complete disease free plantlet using suitable synthetic nutrient media along with plant growth regulators at various concentrations and combinations have been highlighted in this manuscript. Hence, the current review is primarily focused on the applications and its effects of superior biotechnological tools for long term conservation of diverse species of citrus for further increasing the potentiality of Citrus industries in addition to genetic improvement and genetic resource conservation.