Application of Aspergillus aculeatus to rice roots reduces Cd concentration in grain

Abstract

Background and aims: ‘Cd toxicity in rice’ events have resulted in vast public concern and uncertainty. Effective bioremediation could be accomplished via applying microbes that are capable of alleviating Cd content in rice grains. Methods: Here, we investigated the effect of inoculating Aspergillus aculeatus on tolerance, uptake and transportation of Cd in rice cultivated in Cd contaminated growth medium. Results: A. aculeatus facilitated rice growth in Cd polluted growth medium and alleviated Cd toxic effects according to our observations on biomass, leaf and root length and grain yield. Cd accumulation analysis indicated that the plants which were inoculated with A. aculeatus exhibited minimum Cd level in all organs. Particularly in grain we observed a 40.5% reduction compared to the Cd only treated plants. Differences in Cd accumulation in rice inoculated with A. aculeatus might be attributed to the enhancement of cell wall-bound Cd, decreasing the Cd inorganic forms in roots, and inhibiting the expression of OsNRAMP5 and OsNRAMP1. A. aculeatus inoculation also led to minimum growth medium DTPA-Cd concentration, which possibly reduced the availability of the metals for plant uptake. Conclusions: These results suggested that A. aculeatus might potentially be applicable to improve Cd tolerance and reduce Cd transportation in grains of rice.