Table 2.

Direct transformation methods.

Species	Explants	Genes/Molecules	Gene Delivery System	Efficiency (%)	Reference
Barley	Seeds	OsWRKY70, OsWRKY53, and gus	Particle bombardment	-	[71]
Maize	Calli	VHb	Particle bombardment	-	[72]
Sorghum	Immature embryos	NptII	Particle bombardment	46.6%	[73]
Sugarcane	Embryonic calli	cry1Ac and bar	Particle bombardment	-	[74]
Rice	Calli	Cpf1, crRNA, and repair templates	Particle bombardment	8%	[47]
Wheat	Immature embryo	gfp and bar	Particle bombardment	-	[75]
Wheat	Callus	Ppa	Particle bombardment	-	[76]
Palm	Callus	ChoA	Particle bombardment	-	[77]
Blackgram	Embryonic axis	ChiB	Particle bombardment	13%	[78]
Cowpea	Embryonic axis	Arc1	Particle bombardment	-	[79]
Carrizo citrange	Immature epicotyl	nptII and gfp	Particle bombardment	18.4%	[80]
Soybean	Embryogenic cells	Hpt, ZFN expression constructs, and HDR donor	Particle bombardment	About 2.84%	[48]
Zygnematophycean algae	Cells	GFP	Electroporation	-	[81]
Wheat	Immature embryos	bar and uidA	Electroporation	0.4%	[82]
Tomato	Leaves	Fe and Mg	Liposomes	33%	[83]
Maize	Embryogenic callus	gus and bar	Silicon carbide whisker	-	[84]
Cotton	Embryogenic callus	Gus and AVP1	Silicon carbide whisker	Up to 94%	[85]
Cotton	Embryogenic callus	GUS, AVP1, and nptII	Silicon carbide whisker	-	[86]
Peanut	Callus	chitinase and hygromcin	Silicon carbide whisker	6.88%	[58]
Barley	Protoplasts	Act1, gus, and nos	Microinjection	-	[87]
Oil palm	Protoplasts	GFP	Microinjection	10–74.6%	[88]
Maize	Pollen	GFP	Pollen tube pathway	0.86%	[89]
Cotton	Pollen	nptII	Pollen tube pathway	-	[90]
Melon	Pollen	Fom-2	Pollen tube pathway	3.28% and 4.26%	[91]
Peanut	Pollen	AhBI-1	Pollen tube pathway	50%	[92]