Abstract
Rice, a staple crop for nearly half the planet’s population, tends to absorb and accumulate excessive cadmium (Cd) when grown in Cd-contaminated fields. Low levels of Cd can degrade the quality of rice grains, while high levels can inhibit the growth of rice plants. There is genotypic diversity in Cd distribution and Cd tolerance in different rice varieties, but their underlying genetic mechanisms are far from elucidated, which hinders genetic improvements. In this study, a joint study of phenotypic investigation with quantitative trait loci (QTLs) analyses of genetic patterns of Cd distribution and Cd tolerance was performed using a biparent population derived from japonica and indica rice varieties. We identified multiple QTLs for each trait and revealed that additive effects from various loci drive the inheritance of Cd distribution, while epistatic effects between various loci contribute to differences in Cd tolerance. One pleiotropic locus, qCddis8, was found to affect the Cd distribution from both roots to shoots and from leaf sheaths to leaf blades. The results expand our understanding of the diversity of genetic control over Cd distribution and Cd tolerance in rice. The findings provide information on potential QTLs for genetic improvement of Cd distribution in rice varieties.
Highlights
Cadmium (Cd), a heavy metal element that is nonessential and toxic to most organisms, is ubiquitously distributed in soil as a consequence of anthropogenic activities, where it can bring serious damage to crop production (Zhao et al, 2015)
It was found that rice variety “IRAT129” from japonica rice subspecies accumulated low levels of grainCd, while “93-11” from indica rice subspecies accumulated high levels of Cd in grains
We carried out a hydroponic culture experiment to compare their distribution patterns, and the results of Cd level comparison revealed that, regardless of the Cd levels in “IRAT129” and “93-11,” Cd levels in the four tissues were ordered root > node > leaf sheath > leaf blade (Figure 1A)
Summary
Cadmium (Cd), a heavy metal element that is nonessential and toxic to most organisms, is ubiquitously distributed in soil as a consequence of anthropogenic activities, where it can bring serious damage to crop production (Zhao et al, 2015). Exposure to low levels does not tend to disrupt growth and development, but uptake of essential elements, such as Zn, Fe, and Mn, may be hindered by uptake of Cd, and Cd can gradually accumulate in the edible parts, reaching high levels (Benavides et al, 2005; Clemens, 2006; Yamaji and Ma, 2014; Li et al, 2017) This results in changes in physiological and biochemical components followed by a reduction in crop quality, representing a threat to food safety and human health (Clemens et al, 2013; Zhao et al, 2015).
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