Quantitative trait loci (QTL) and candidate genes associated with trace element concentrations in perennial grasses grown on phytotoxic soil contaminated with heavy metals

Abstract

Background and aims Native grasses planted or growing on sites contaminated by heavy metals should be safe for livestock and wildlife. Plant breeders seek to identify genes and quantitative trait loci (QTLs) controlling trace element variation among these grasses. Methods QTLs controlling forage mineral concentrations were mapped in a population derived from two perennial wildrye species, Leymus cinereus and Leymus triticoides, grown in soil contaminated with arsenic, cadmium, copper, lead, zinc, and other trace elements. These QTLs were aligned to the genome sequence of barley (Hordeum vulgare) for comparison to genes or QTLs controlling trace element uptake in other species and soils, including perennial wildrye grown in fertile soil.Results A total of 25 QTLs for 14 elements were detected on contaminated soil. Three of four zinc QTLs were conserved between fertile and contaminated soils, but no other QTLs were conserved across these test soils. Two homoeologous molybdenum QTLs were closely associated with MOT1 orthogenes, which encode one of two known molybdate transporters in plants, and possible candidate gene associations were identified for other heavy metal QTLs. Conclusions Results elucidate conserved and unparalleled mechanisms controlling trace element variation among different plants and soils, showing opportunities and challenges in plant breeding.Each year, millions of tonnes of new trace metals including arsenic (As), cadmium (Cd), copper (Cu), manganese (Mn), molybdenum (Mo), lead (Pb), and zinc (Zn) are produced by mines and mobilized into the biosphere (Nriagu and Pacyna 1988;Moore and Luoma 1990). Humans, plants and animals require Cu, Mo, Mn, Zn and other trace elements including iron (Fe) and magnesium (Mg) as essential micronutrients, but these metals can be toxic to most plants and animals at higher concentrations (Welch 1995;Corah 1996;Grusak and DellaPenna 1999;He et al. 2005; White and Broadley 2005; White and Brown 2010). Other trace metals including As, Cd, and Pb are not essential Plant Soil

Genome-wide association study (GWAS) reveals genetic loci of lead (Pb) tolerance during seedling establishment in rapeseed (Brassica napus L.)

“…Breeding rapeseed cultivars with Pb-tolerant require germplasms and genetic loci related to Pb tolerance. Whereas, more and more genotypes tolerance to Pb toxicity have been selected in rice, ramie and willow populations, very few Pb-tolerant B. napus germplasm has been investigated [12][13][14][15][16][17]. At the vegetative and adult stage, Pb toxicity in rapeseed was evident from elevated levels of oxidative stress and subcellular damage that significantly inhibited plant growth, leaf chlorophyll contents, gas exchange parameters and photosynthetic attributes [18][19][20][21].…”

“…Previous research has also demonstrated that HvCBT1 (CaM binding transporter) in barley, AtCNGC1 (cyclic nucleotide-gated ion channel) in Arabidopsis and NtCBP4 in tobacco, as one of the nonselective entry pathways used by Pb [28][29][30][31]. For further exploring genetic factors responding to Pb stress, Genome-wide association study (GWAS), a powerful tool to detect the genetic architecture of complex traits, has been widely used in rice, maize and grasses [12,[32][33][34][35][36][37][38][39]. GWAS has also been used to study HMs concentration, tolerance to Cd and other abiotic stress related quantitative trait loci (QTLs), but not the molecular mechanism of Pb tolerance in B. napus [23,[40][41][42][43].…”

Genome-wide association study (GWAS) reveals genetic loci of lead (Pb) tolerance during seedling establishment in rapeseed (Brassica napus L.)

“…Breeding rapeseed cultivars with Pb-tolerant require germplasms and genetic loci related to Pb tolerance. Whereas, more and more genotypes tolerance to Pb toxicity have been selected in rice, ramie and willow populations, very few Pb-tolerant B. napus germplasm has been investigated [12][13][14][15][16][17]. At the vegetative and adult stage, Pb toxicity in rapeseed was evident from elevated levels of oxidative stress and subcellular damage that significantly inhibited plant growth, leaf chlorophyll contents, gas exchange parameters and photosynthetic attributes [18][19][20][21].…”

“…Previous research has also demonstrated that HvCBT1 (CaM binding transporter) in barley, AtCNGC1 (cyclic nucleotide-gated ion channel) in Arabidopsis and NtCBP4 in tobacco, as one of the nonselective entry pathways used by Pb [28][29][30][31]. For further exploring genetic factors responding to Pb stress, Genome-wide association study (GWAS), a powerful tool to detect the genetic architecture of complex traits, has been widely used in rice, maize and grasses [32][33][34][35][36][37][38][39][40]. GWAS has also been used to study HMs concentration, tolerance to Cd and other abiotic stress related quantitative trait locus (QTL), but not the molecular mechanism of Pb tolerance in B. napus [23, [41][42][43][44].…”

Genome-wide association study (GWAS) reveals genetic loci of lead (Pb) tolerance during seedling establishment in rapeseed (Brassica napus L.)

“…Breeding rapeseed cultivars with Pb tolerant require germplasms and genetic loci related to Pb tolerance. Whereas, more and more genotypes tolerance to Pb toxicity have been selected in rice, ramie and willow populations, very few Pb tolerant B. napus germplasm has been investigated [12][13][14][15][16][17]. To determine plants are able to tolerate heavy metals (HMs) or not, toxicity effect of HMs on the initial stages such as seedling establishment of a plant have been widely studied in Brassica species [18][19][20][21].…”