TABLE 2.

Summary of key GWA studies for toxic metals/metalloids toxicity in different crop plants.

Metals/metalloids	Plant species	Platform	No. of QTLs	No. of lines/accessions used	Chromosome	SNPs	Key observations	References
Cadmium	Brassica napus	Illumina Brassica SNP60 Bead chip	25	419	A3, A5, A9, C3, C5, C8	98	QTLs identified for root, shoot, and for Cd translocation. Homologs of key Arabidopsis genes identified that can be further used for Cd tolerance in other plants.	Chen et al., 2018
Cadmium	Oryza sativa	SLAF-seq, Illumina-HiSeq 2500	35	338	1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12	203	Identified 35 significant QTLs for low Cd accumulation, including a novel QTL, qCd1-3.	Pan et al., 2020
							Differential expression of OsABCB24, a candidate gene underlying qCd1-3.
Cadmium, iron, and zinc	Triticum aestivum	Illumina iSelect 90K	5	120	1A, 1D, 2B, 6D	179	Five novel loci detected to be associated with Cd toxicity.	Safdar et al., 2020a
Copper	Triticum aestivum	Wheat 660K SNP assay	4	243	1D, 6A, 6B, 7D	489	Four significant QTLs with a phenotypic variation of 4.71–8.66% regulating GCC in wheat were observed.	Zhao et al., 2020
Lead	Brassica napus	60 K Brassica Infinium SNP array	4	472	A9, C3, C4	9	Identified four QTLs and nine candidate genes associated with Pb tolerance.	Zhang et al., 2020a
Iron and zinc	Oryza sativa	50 K SNP chip	29	192	1, 2, 3, 4, 6, 7, 8, 9, 10	31,132	Total of 29 marker-trait associations (MTAs) were identified, showing a phenotypic variation of up to 53% for traits controlling Fe and Zn contents.	Bollinedi et al., 2020
Iron	Oryza sativa	384 SNP chip	8	288	1, 2, 3, 4, 7	384	Three LD blocks containing QTLs for Fe toxicity tolerance were found that can be used for rice breeding programs for specific land types.	Utami et al., 2020
Iron	Glycine max	Illumina Infinium SoySNP50K BeadChip	69	460	3, 5, 16	36,000	Integration of approaches like genome-wide association (GWA), genome-wide epistasis (GWE), and gene expression enabled identification of novel Fe tolerance QTLs, with a significant QTL found on chromosome Gm03.	Assefa et al., 2020
Potassium	Hordeum vulgare	Diversity Array Technology (DArT)	3	179	1H, 6H	13,634	Identified three significant QTLs associated with K uptake and translocation.	Ye et al., 2020
Potassium	Triticum aestivum	90 K Infinium SNP array	11	150	1A, 1B, 1D, 2A, 3A, 3B-I, 3B-II, 4A-I, 4A-II, 4B, 5B-I, 5B-II, 6A, 6B, 7A, and 7B	20,853	Total of 534 significant MTAs were identified for potassium related traits, which included 11 stable loci and 16 M-QTLs.	Safdar et al., 2020b
							Identified potential candidate genes involved in crucial pathways related to stress tolerance, nutrient uptake, and sugar metabolism.
Aluminum and iron	Oryza sativa	44 K SNP array	6	373	1, 2, 9, 12	36,901	Identified forty eight regions associated with Al tolerance. Six Al tolerant QTL were detected for root growth, out of which three (ART1, STAR2, Nrat1) were used to induce Al sensitive rice mutant.	Famoso et al., 2011
							Promoted the selectively introgressing alleles for trait enhancement