Abstract:

Contamination of toxic heavy metals in soil not only causes the reduction of crop yield, but also poses a potential threat to human health due to their uptake and accumulation in edible parts of crops. The heavy metals accumulation in rice grain varies with genotypic, environmental and their interaction. However, little is known about genotypic and environmental effect on the toxic heavy metal accumulation in rice grain. In this study, the genotypic and environmental variations of Cd, Cr, As, Ni and Pb concentrations in rice grains, and the relationships between these heavy metals and Fe, and Zn were investigated by using twelve japonica rice genotypes, planted at six locations in five cities (Jiaxing, Huzhou, Hangzhou, Shaoxing and Ningbo) of Zhejiang Province, China (Table 1). The results showed that genotypic and environmental effects, and their interaction were all highly significant for these five heavy metal concentrations in rice grains (Table 2 and Table 3). It was suggested that the concentration of these heavy metals in grains of rice could be reduced through genetic and agronomic improvement. Meanwhile, the stabilization coefficient of these heavy metal concentrations in rice grains varied with environment, genotype as well as individual metal element, indicating the importance of rice cultivar based on environmental conditions. In addition, soil pH affected not only soil heavy metal availability and grain heavy metal concentrations, but also the stability (interaction of genotype by environment) in grain heavy metal accumulation (Table 4). Correlation analysis indicated Cd and Cr, As or Ni, As and Cr, and Pb and As levels in soil, and Cd and As or Pb, Cr and Ni, and As and Pb concentrations in rice grains were closely correlated (Table 5). More investigation should be done to determine the relationships between mineral nutrients and toxic heavy metals in their availability in soil and accumulation in rice for developing the rice cultivars with a desirable concentration of nutrient elements and lower concentration of the toxic heavy metals.

Key words: Rice (Oryza sativa L.), Grain, Heavy metal, Genotype, Environment