Data_Sheet_1_Selenium Effect Threshold for Soil Nematodes Under Rice Biofortification.xlsx

Crop biofortification with inorganic selenium (Se) fertilizer is a feasible strategy to improve the health of residents in Se-deficient areas. For eco-friendly crop Se biofortification, a comprehensive understanding of the effects of Se on crop and soil nematodes is vital. In this study, a rice pot experiment was carried out to test how selenite supply (untreated control (0), 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 100, or 200 mg Se kg−1) in soil affected rice growth, rice Se accumulation, and soil nematode abundance and composition. The results showed that selenite supply (5–200 mg kg−1) generally increased the number of rice tillers, rice yield, and Se concentrations in rice grains. In soil under 10 mg kg−1 Se treatment, the genus composition of nematodes changed significantly compared with that in the control soil. With increased Se level (> 10 mg kg−1), soil nematode abundance decreased significantly. Correlation analysis also demonstrated the positive relationships between soil Se concentrations (total Se and bioavailable Se) with rice plant parameters (number of rice tillers, rice yield, and grain Se concentration) and negative relationships between soil Se concentrations (total Se and bioavailable Se) with soil nematode indexes (nematode abundance and relative abundance of Tobrilus). This study provides insight into balancing Se biofortification of rice and soil nematode community protection and suggests the effective concentrations for total Se (1.45 mg kg−1) and bioavailable Se (0.21 mg kg−1) to soil nematode abundances at 20% level (EC20) as soil Se thresholds. At Se concentrations below these thresholds, rice plant growth and Se accumulation in the grain will still be promoted, but the disturbance of the soil nematodes would be negligible.施用无机硒（selenium, Se）肥料开展作物硒生物强化，是改善缺硒地区居民健康的可行策略。要实现环境友好型的作物硒生物强化，全面解析硒对作物及土壤线虫的影响至关重要。本研究通过水稻盆栽试验，探究了土壤中亚硒酸盐施用量（未处理对照组（0）、5、10、15、20、25、30、35、40、45、50、100及200 mg Se kg⁻¹）对水稻生长、水稻硒积累量以及土壤线虫丰度与群落组成的影响。结果表明，施用量为5~200 mg kg⁻¹的亚硒酸盐总体上可提升水稻分蘖数、稻谷产量及籽粒硒含量。当土壤硒施用量为10 mg kg⁻¹时，线虫属水平群落组成与对照组土壤相比发生显著变化；当硒施用量超过10 mg kg⁻¹时，土壤线虫丰度显著下降。相关性分析显示，土壤总硒与有效态硒浓度与水稻生长参数（分蘖数、稻谷产量及籽粒硒含量）呈显著正相关，而与土壤线虫指标（线虫丰度及突唇属（Tobrilus）相对丰度）呈显著负相关。本研究为平衡水稻硒生物强化与土壤线虫群落保护提供了理论参考，并提出以土壤线虫丰度降低20%时的阈值浓度（EC20）作为土壤硒安全阈值：总硒为1.45 mg kg⁻¹，有效态硒为0.21 mg kg⁻¹。当土壤硒浓度低于该阈值时，水稻生长与籽粒硒积累仍可得到促进，且对土壤线虫群落的干扰可忽略不计。