TABLE 1.

Physical, biological, and chemical conventional transformation methods in plants.

Delivery method	Plant–host range	Target tissue	Advantages	Adverse effects or disadvantages	References
Physical
Electroporation	Unrestricted	Pollen grains, protoplasts, and meristems	Simple, fast, and inexpensive as well as wide a plant–host range	Non-specific transport of material and damage to the target tissue	Cunningham et al., 2018; Keshavareddy et al., 2018; Sangeetha et al., 2019; Ramkumar et al., 2020
Biolistic	Unrestricted	Microspores and intact tissue	Suitable for large-sized genetic cargo	Scrambled and multiple integrations, damage to the target tissue, and specialized equipment is required	Altpeter et al., 2005; Gao C. et al., 2008; Cunningham et al., 2018; Lacroix and Citovsky, 2020; Ramkumar et al., 2020
Biological
Agrobacterium	Restricted	Immature tissues (e.g., callus and meristems) and cells	Stable gene integration, high-efficiency transformation, and no specialized equipment is required	High host specificity and limited to DNA cargo	Ishizaki et al., 2008; Sood et al., 2011; Krenek et al., 2015; Cunningham et al., 2018; Keshavareddy et al., 2018
Viral vectors	Restricted	Immature tissues (e.g., callus and meristems) and cells	Easy to set up, quick, and affordable	High host specificity and limited cargo size	Jones et al., 2009; Cunningham et al., 2018; Keshavareddy et al., 2018
Chemical
Polymers (polyethylene glycol)	Unrestricted	Protoplasts	Various genetic cargo types (DNA, siRNA, and miRNA) and economical procedure	High concentrations induce toxicity	Cunningham et al., 2018; Yu et al., 2020