Department of Microbiology, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand.
Department of Microbiology, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand; Research Center for Environmental and Hazardous Substance Management, Khon Kaen University, Khon Kaen 40002, Thailand.
Ecotoxicol Environ Saf. 2023 Feb;251:114535. doi: 10.1016/j.ecoenv.2023.114535. Epub 2023 Jan 12.
This study investigated the effects of the plant growth-promoting endophytic bacterium Cupriavidus taiwanensis KKU2500-3 on the growth of KDML105 rice plants and cadmium (Cd) accumulation in grains. The rice plants were cultivated in soils with 20 and 50 ppm Cd under greenhouse conditions for two consecutive years. At both levels, Cd reduced rice growth and development. Under Cd stress, KKU2500-3 colonized the root surface and interior of rice plants at the early growth stage, and this colonization remained until the late stage. The colonized bacteria increased the pigment contents but reduced the root-to-aboveground translocation of Cd. In soil with 20 ppm Cd, the phytochelatin content of the bacteria-inoculated rice was lower (32.3-89.3%) than that of uninoculated rice. In soil with 50 ppm Cd, the bacteria-inoculated rice exhibited higher glutathione reductase (5-63%) and proline (5-115%) levels, a higher reduced glutathione (GSH)/0.5 oxidized glutathione (GSSG) ratio (4-212%) and decreased lipid peroxidation (1-19%) compared with uninoculated rice. The root-to-grain translocation factor of inoculated rice in soil with 50 ppm Cd was significantly lower than that of inoculated rice in soil with 20 ppm Cd, and this finding was consistent with the 38.6% and 75.1% reductions in Cd accumulation observed in grains from soils with 20 and 50 ppm Cd, respectively. The Cd content of KDML105 grains grown in soil with 50 ppm Cd was 0.36 ppm, which is below the Codex standard for polished rice (0.4 ppm). The levels of available P, Zn, and SO also affect Cd availability in soil, and colonized KKU2500-3 showed varying responses to different Cd levels. Thus, bacterial inoculation, the Cd level and soil properties play important roles in Cd accumulation in KDML105 rice grains. The role of C. taiwanensis KKU2500-3 on the production of low-Cd-accumulating rice in paddy fields contaminated with a range of Cd levels should be further investigated.
本研究调查了植物促生内生细菌 Cupriavidus taiwanensis KKU2500-3 对 KDML105 水稻植株生长和籽粒中镉（Cd）积累的影响。在温室条件下，连续两年在含有 20 和 50 ppm Cd 的土壤中种植水稻。在这两个水平下，Cd 都降低了水稻的生长和发育。在 Cd 胁迫下，KKU2500-3 在早期生长阶段定殖在水稻根系表面和内部，并一直持续到后期。定殖细菌增加了色素含量，但减少了 Cd 的根到地上部转运。在含有 20 ppm Cd 的土壤中，接种细菌的水稻的植物螯合肽含量比未接种的水稻低（32.3-89.3%）。在含有 50 ppm Cd 的土壤中，接种细菌的水稻表现出更高的谷胱甘肽还原酶（5-63%）和脯氨酸（5-115%）水平、更高的还原型谷胱甘肽（GSH）/0.5 氧化型谷胱甘肽（GSSG）比值（4-212%）和降低的脂质过氧化（1-19%）。与未接种的水稻相比，在含有 50 ppm Cd 的土壤中，接种水稻的根到籽粒的转运因子显著降低，这与在含有 20 和 50 ppm Cd 的土壤中观察到的籽粒中 Cd 积累分别减少 38.6%和 75.1%的结果一致。在含有 50 ppm Cd 的土壤中生长的 KDML105 稻谷的 Cd 含量为 0.36 ppm，低于 Codex 抛光米标准（0.4 ppm）。土壤中有效磷、锌和 SO 的水平也影响 Cd 的有效性，定殖的 KKU2500-3 对不同 Cd 水平表现出不同的反应。因此，细菌接种、Cd 水平和土壤性质在 KDML105 水稻籽粒中 Cd 积累方面起着重要作用。C. taiwanensis KKU2500-3 在含有不同 Cd 水平的稻田中生产低 Cd 积累水稻的作用，应进一步研究。
