Rhizosphere microecological effects of stachyose amendment in heavy metal contaminated soils

To further investigate how plant root secretions actively reshape the inter-root microbial community to enhance their own adversity tolerance, this study investigated the inter-root microecological effects and the mechanism of enrichment of probiotic bacteria by the differential inter-root secretion of fenugreek, under cadmium stress. The results showed that, at the genus level, fructose treatment significantly enriched bacteria of the genus Massilia, and its representative strain Massilia oculi CCUG 43427A (BC18) was successfully isolated. The results of the pot experiment indicated that BC18 significantly reduced the exchangeable state of soil cadmium (Cd) and significantly promoted the root length and fresh weight of tomato seedlings, in which the fresh weight increased significantly by 79.23% (p < 0.05) and the root length increased significantly by 17.64% (p < 0.05). In the liquid culture medium, the growth of BC18 was significantly enhanced by fructose application. The biofilm production was significantly increased by 89.28% (p < 0.05) compared with the control, the IAA-producing capacity was substantially improved, and the removal rate of Cd was increased to 71.65%. The results suggest that under the stress of cadmium pollution, tomato seedlings may assist the plant to resist Cd stress by releasing fucose to recruit probiotic bacteria of the genus Massilia, blunting soil heavy metal Cd and promoting plant growth. The study results may provide a scientific basis for helping plants to resist environmental stress by regulating the inter-root microbiome.