Breeding of new rice varieties for phytoextracting cadmium from paddy soil

Tadashi Abea, M. Itob, R. Takahashib, T. Honmac, N. Sekiyad,e, K. Shiraof, M. Kuramataa, M. Murakamia and S. Ishikawaa.

aInstitute for Agro-environmental Sciences, NARO, Japan.

bAkita Prefectural Agricultural Experiment Station, Japan.

cNiigata Agricultural Research Institute, Japan.

dNagano Agricultural Experiment Station, Japan.

eNagano Animal Industry Experiment Station, Japan.

fKumamoto prefectural Agricultural Research Center, Japan.

tadabe@affrc.go.jp

Phytoextraction is an attractive technique to remove cadmium (Cd) from soils because it is cost-effective and environmental friendly. High-Cd accumulating rice varieties (henceforce: high-Cd rice), especially, are desirable to remove Cd from paddy soils. However, such varieties so far are all indica-type and they are not suitable for the practical cultivation in Japan because of high shattering and easy lodging habit, resulting in unfit for mechanical harvesting. In this study, we attempted to develop practical high Cd varieties with non-shattering and lodging resistance that are suitable for the Japanese rice cultivation systems.

Three practical high Cd rice varieties were developed:

A variety name "Phytoremediation CD No.1" is characteristics of non-shattering and lodging resistance with short culm. This variety was produced by a gamma ray mutation method from an indica-type, a high-Cd rice variety “Jarjan”.

"Phytoremediation CD No. 2" is non-shattering and strong culm. This variety was developed by crossing of “Jarjan” and “Tachisugata” which is a rice variety for whole crop silage use. DNA markers were used to introduce Jarjan OsHMA3 allele showing high-Cd accumulation and Tachisugata qSH1 allele showing a non-shattering habit.

"Phytoremediation CD No.3" is also non-shattering and lodging resistance. In addition, this variety showed substantially high-Cd accumulation ability via pyramiding of several genes of high-Cd traits.

In four field trials, the amounts of Cd accumulation in aerial part of "Phytoremediation CD No.1" was 3.6 to 16.7 times higher than those of leading edible japonica rice varieties (control varieties). "Phytoremediation CD No.2" accumulated Cd at 7.0 to 14.2 times higher than the control varieties, and "Phytoremediation CD No.3" showed 7.7 to 12.1 times higher than the controls.

We achieved producing three new varieties carrying necessary traits of high-Cd accumulation, non-shattering, and lodging resistance. In addition, we confirmed that these varieties have high practicability for phytoextraction use in the Japanese paddy fields.

We expect that use of these varieties for extracting Cd will be a good method to reduce Cd concentrations in edible rice grains.

This work was supported by a grant from the Ministry of Agriculture, Forestry, and Fisheries of Japan [Genome for Agricultural Innovation, QT-4006, Regulatory Research Projects for Food Safety, Animal Health and Plant Protection, no. 2603].

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