TABLE 1.

Summary of selectable markers and techniques used to create SMG-free engineered rice.

S. no.	Method(s) used to generate SMG-free Plants	Selectable marker gene	Target gene(s)	Target Trait	References
1	Co-transformation	HPT and NPT-II	GUS	GUS activity in plant leaves	Komari et al. (1996)
2	Co-transformation	HPT	uidA	Gus activity in rice transgenic cells	Huang et al. (2001)
3	Co-transformation	HPH, Bar	Rice ragged stunt virus (RRSV)	Viral resistance	Lu et al. (2001)
4	R/RS site-specific recombination + Ac transposable elements	HPT and NPT-II	R gene of zygosaccharomyces rouxii	Generation of deletion in rice genome	Nakagawa et al.(2001)
5	Ac/Ds transposon system	HPH	cry1B	Insect resistance	Cotsaftis et al.(2002)
6	R/RS site-specific recombination	IPT	Gus A, NPTII, and hpt	Model genes of interest	Endo et al. (2002)
7	Co-transformation	HPT	glutelin A (Antisense)	Glutelin content in seeds	Maruta et al. (2002)
8	Co-transformation	HPT and PMI	Phytoene synthase (psy), lycopene β-cyclase (lcy), and phytoene desaturase (crtI)	Caroteneoid accumulation	Datta el al. (2003)
9	Co-transformation	HPH	cryIAb/cryIAc	Insect resistance (yellow stem borers and leaf-folders)	Tu et al. (2003)
10	Co-transformation	HPT	bar	Herbicide resistance	Breitler et al. (2004)
11	Co-transformation	NPT-II and HPH	crtI , psy, and lyc	Caroteneoid accumulation	Parkhi et al. (2005)
12	Cre/loxP site-specific recombination	IPT	79 bp of XVE	—	Sreekala et al. (2005)
13	Co-transformation	HPH	psy, crtI, and lyc	Accumulation of provitamin A in the endosperm tissue	Baisakh et al. (2006)
14	Cre/loxP site-specific recombination	HPT	Vitreoscilla hemoglobin (VHb), trans-zeatin synthetase (tzs), and modified 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS)	—	Cao et al. (2006)
15	Co-stranformation	HPH	chip (pistil chitinase )	Pistil-predominant chitinase (blast-disease resistance)	Hashizume et al. (2006)
16	Co-transformation	HPT	Amphipathic protein (APl)	Enhanced disease resistance	Yu et al. (2006)
17	Co-transformation	HPT	Xa21	Bacterial blight (BB) resistance	Xia et al. (2006), Gao et al. (2011)
18	Co-transformation	HPT	Human lactoferrin (hLF), a lysine-rich protein gene from potato (SB401), and a methionine-rich protein gene from rice (RZ10)	—	Li et al. (2007)
19	Co-transformation	Bar	CecropinB	Resistance against a range of plant pathogenic bacteria (Xanthomonas compestris pv oryzae)	Zhao et al. (2007)
20	Cre/loxP site-specific recombination	NPT-II	Gus controlled by OsMAD45	Gus assay (Expression pattern of OsMAD45 promotor)	Bai et al. (2008)
21	Co-transformation	HPH	gluA-4XCII250–270	Accumulating a type II-collagen tolerogenic peptide	Hashizume et al. (2008)
22	Co-transformation	HPH	Rice chitinase (chi11)	sheath blight resistance	Sripriya et al. (2008)
23	Co-transformation	HPT	Cry1Ab	Lepidopteran Pest Resistance	Qi et al. (2009)
24	Co-transformation	HPT	cryIA(c)	resistance to chewing insects	Yu H. X. et al. (2009)
25	Co-transformation	HPT	Waxy (Wx)	high amylose content (AC)	Yu H. et al. (2009)
26	Co-transformation	HPT	cry1B-1Aa	Insect resistance (yellow stem borer)	Kumar et al. (2010)
27	Cre/lox site-specific recombination	HPT	ASAL	Resistance to sap-sucking planthoppers	Sengupta et al. (2010)
28	Co-transformation	HPH	chi11	Sheath blight disease resistance	Ramana Rao et al. (2011)
29	Cre/loxP site-specific recombination	NPT	Gus A	GUS assay	Khattri et al. (2011)
30	Cre/loxP site-specific recombination	NPT and HPT	GUS driven by maize ubiquitin promoter	GUS activity	Nandy and Srivastava, (2012)
31	Ac/Ds transposon system	HPT	partial sequences of the first intron of rice epsps	—	Li and Charng, (2012)
32	Co-transformation	HPT	inverted-repeat (IR) structures targeting the rice stripe virus (RSV) coat protein (CP) and the special-disease protein (SP)	Resistance to rice stripe virus (RSV )	Jiang et al. (2013)
33	Co-transformation	HPT-II	High Molecular Weight Glutenin Subunits (HMW-GS) Gene- Glu-1Bx	Increasing bread-making quality	Park et al. (2013)
34	Co-transformation	HPT	cry1Ab	Insect resistance (silkworm)	Qi et al. (2013)
35	Co-transformation	HPT	Phytoferritin	Increase iron content	Oliva et al. (2014)
36	Piggy bac mediated transposition	HPT	ALS	Herbicide bispyribac sodium (BS)-tolerant	Nishizawa-Yokoi et al. (2015)
37	Co- transformation	HPT-II	Glu-1Dy10	Increasing quality processing of bread and noodles	Park et al. (2014)
38	Co- transformation	HPT	Bt	Insect resistance	Gao et al. (2015)
39	FLP/FRT site-specific recombination	HPT	NtTC	Enhanced seed tocopherol content	Woo et al. (2015)
40	Alternative selection marker	HPT	ptxD	Weed control in rice	Manna et al. (2016)
41	Cre/loxPsite-specific recombination	HPT-I	vip3BR	Broad-spectrum insect resistance	Pradhan et al. (2016)
42	Co-transformation	HPT	RNAi targeting RBSDV (rice black-streaked dwarf virus)	Developing resistance	Ahmed et al. (2017)
43	Co-transformation	HPT	NmDef02 antifungal defensin.	Resistance against phytopathogenic fungus Sarocladium oryzae	Perez-Bernal et al. (2017)
44	Co-transformation	HPT	AmA1	Production of essential amino acids in rice seeds	Xu et al. (2017)
45	Cre/loxPsite-specific recombination	HPT, NPT-II, BAR	OsB1, OsB2, OsDFR, OsC1	Purple endosperm	Zhu et al. (2017)
46	Co-transformation	HPT	cry2AX1	Insect resistance	Rajadurai et al. (2018)
47	CRISPR	DsRED fluorescence	IAA methyltransferase (IAMT)	The difficulty for hypocotyl reorientation under gravistimulation increased growth rate of pollen tube	Aliaga-Franco et al. (2019)
48	CRISPR-Cas9 RNP	Hygromycin	DROOPING LEAF (DL)	Drooping leaf phenotype	Toda et al. (2019)
49	Co-transformation	HPT	SSSII-2	Soft kernels	Xu et al. (2020)
50	CRISPR-Cas9 RNP (co-delivered with plasmid)	HPT	PDS	Albino phenotype	Banakar et al. (2020)
51	CRISPR-Cas9	Hygromycin	SSU-crtI and ZmPsy	Enrichment of carotenoids in seeds	Dong et al. (2020)
52	Co-transformation	HPT	RNAi targeting RBSDV (rice black-streaked dwarf virus)	Developing resistance	Feng et al. (2021)
53	Ac/Ds transposon system	Green and Red Fluorescence	Pi21	Rice blast disease	Li et al. (2021)
54	Alternative selection marker	HPT,NPT II	ptxDq	Catalytic activity	Liu et al. (2021)