Chinese researchers WU Yuejin and his team with Institute of Technical Biology and Agriculture Engineering, Hefei Institutes of Physical Science studied several indica and japonica rice cultivars under different cadmium (Cd) treatment levels, and then revealed the differences of Cd accumulation between these two rice subspecies in the reproductive stage.

Excessive Cd in rice grains is of great concern worldwide, particularly in southern China where heavy metal pollution in the soil is widespread. Cd causes many morphological, physiological, biochemical, and structural changes in growing plants, which ultimately leads to a decline in productivity.

Much work has been done regarding the key genes responsible for Cd absorption, transport, and accumulation in rice, but little is known about the differences of Cd accumulation between indica and japonica rice cultivars during the reproductive stage.

To solve this problem, WU's team studied the Cd absorption, transport, and accumulation of indica and japonica cultivars at low, moderate, and heavy treatment levels.

They discovered that Cd accumulation of aerial parts in indica cultivars was associated with a significantly higher absorption rate of shoots during the reproductive period.

It was likely that the Cd in the sheath of the indica cultivars was continuously exported to the grain with the transfer of nutrients during the reproductive stage. The early postheading stage played a major role in the Cd accumulation in rice grains. Therefore, flood irrigation should be carried out at the early grain-filling stage for Cd mitigation in rice grains.

The tested japonica cultivars met the cereal Cd limits of China (0.2 mg kg^-1) under low and moderate soil Cd pollution.

This work is particularly important in southern China, where soil pollution is dominated by a low Cd level. And the team believes their work would be helpful for the selection of proper cultivars and field management practices to alleviate Cd exposure risk in rice production.

This work was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences, the National Key R&D Program of China, the National Natural Science Foundation of China, Anhui Science and Technology Major Project, and the Science and Technology Service Network Initiative of the Chinese Academy of Sciences.