Water management is an economic and effective strategy to reduce arsenic (As) accumulation in rice grains, but little is known about the effect of water management on the migration and transformation of As in the soil-rice system. In this study, the effect of the continually (CF) and intermittent flooding (IF) treatments on the dynamic change of As in the rhizosphere soil-pore water-iron plaque-rice system was systematically investigated using pot experiments. The expressions of genes involved in As uptake and translocation in rice plants under different water management treatments were further examined. Results showed that the total As concentration in brown rice was increased by 50.8% in the CF treatment compared to the IF treatment, and dimethylarsinic acid (DMA) made greater contribution (from 15.5% to 29.2%) to total As increase in brown rice under the CF treatment. The CF treatment increased As bioavailability in the rhizosphere soil and soil pore water, which enhanced As uptake and transport to the xylem in rice plants by inducing the expressions of silicon transporter genes (OsLsi1 and OsLsi2) compared to the IF treatment. Moreover, the CF treatment increased As translocation from roots to shoots by reducing soil available sulfur and phytochelatins (PCs) biosynthesis and vacuolar sequestration in rice roots compared with the IF treatment. The study provides insight into the physiological and molecular mechanisms underlying As uptake and translocation in rice plants under different water regimes, which will be helpful for adopting the irrigation technique to mitigate excessive As accumulation in rice grains and associated health risk to humans.

Cadmium (Cd) pollution in paddy soils causes a great threat to safe rice production in China. In this review, we summarized the key advances in the research of Cd pollution sources and statuses in Chinese soil and rice, explore the mechanisms of Cd transformation in the rice–soil system, discuss the agronomic strategies for minimizing Cd accumulation in rice grains, and highlight advancements in developing rice cultivars with low Cd accumulation. Anthropogenic activity is a main source of Cd in farmland. Cd in soil solutions primarily enters rice roots through a symplastic pathway facilitated by transporters like OsNRAMP5, OsIRT1, and OsCd1, among which OsNRAMP5 is identified as the primary contributor. Subsequently, Cd translocation is from roots to grains through the xylem and phloem, regulated by transporters such as OsHMA2, OsLCT1, and OsZIP7. Meanwhile, Cd sequestration in vacuoles controlled by OsHMA3 plays a crucial role in regulating Cd mobility during its translocation. Cd accumulation in rice was limited by the available Cd concentration in soil solutions, Cd uptake, and translocation in rice plants. Conventional agronomic methods aimed at reducing grain Cd in rice by suppressing Cd bio-availability without decreasing soil Cd content have been proven limited in the remediation of Cd-polluted soil. In recent years, based on the mechanisms of Cd absorption and translocation in rice, researchers have screened and developed low-Cd-accumulation rice varieties using molecular breeding techniques. Among them, some new cultivars derived from the null mutants of OsNRAMP5 have demonstrated a more than 93% decrease in grain Cd accumulation and can be used for applications in the next years. Therefore, the issue of Cd contamination in the rice of China may be fully resolved within a few years.

Heavy metal pollution, particularly cadmium (Cd) contamination in water and farmland, might accumulate in natural insect enemies through the food chain. In response to this heavy metal stress, natural enemy insects adapt by altering their metabolism and behaviors. As a result, this investigation aimed to elucidate how the development, reproduction, and feeding of Harmonia axyridis Pallas (Coleoptera: Coccinellidae) are affected under Cd contamination. Compared to the control group, the developmental period of H. axyridis was prolonged, with decreased survival, predation, and body weights. Notably, adult insects exhibited deformation, including molting difficulties and wing deformities, which indicated reduced fitness. The ovarian development of female insects was delayed with reduced size, and the pre-oviposition period was prolonged under Cd contamination. Additionally, the hatching rate of offspring was significantly reduced. The Vitellogenin 1 (Vg1) and Vitellogenin 2 (Vg2) exhibited considerable changes throughout their developmental stages. Our results confirmed that the accumulation of Cd has a significant impact on the growth, development, and normal molting of H. axyridis, affecting the reproduction of H. axyridis. The aforementioned results provide valuable insights into the potential ecological effects of Cd accumulation on the food chain, which can inform strategies for pest control, ecosystem stabilization in rice fields, and potentially novel bioremediation approaches. Thereby establishing a theoretical foundation for pest control and ecosystem stabilization in rice fields under Cd contamination while simultaneously providing novel insights for bioremediation strategies.

Fungal contamination in rice and mycotoxins present significant challenges to both rice quality and food safety. However, there is a dearth of comprehensive research on the compositional and structural changes within fungal colonies in rice, particularly in typical rice-producing regions, as well as their underlying influencing factors. In this study, a comprehensive analysis of fungal taxa in rice grains was conducted using amplicon sequencing and bioinformatics methods on 99 rice samples collected in three major rice-producing regions in China: Northeast Plain (NP), Yangtze River Basin (YR), and Southeast Coastal Area (SC). A total of 6,019,722 fungal ITS sequences were obtained with an average sequence length of 235 base pairs, and effective ASVs (2014) accounted for approximately 97.58% of the total ASVs (2064). The fungal community diversity in rice grains exhibited significant variations across the three regions, with deterministic processes playing a predominant role in shaping the ecological dynamics of fungal taxa. Among the core microbiota (92 shared ASVs), the first five species (Alternaria, Fusarium, Curvularia, Epicoccum, and Ustilaginoidea) accounting for a proportion greater than 5% had been reported as potential pathogens for plants. Geographical variations in fungal community composition were evident, with a significantly higher number of shared populations observed between YR and CS regions compared to those in the NP region. Nutrient elements and climatic conditions were the internal and external driving factors of rice fungal community composition. Additionally, notable regional variations in fungal functionality were observed. The findings have significant implications for gaining a comprehensive understanding of the distribution patterns of fungal communities in the major rice-producing regions in China. Additionally, it provides valuable insights into controlling key influencing factors to effectively reduce the occurrence of toxin-producing fungi and mitigate the associated risks related to mycotoxin contamination, thereby contributing to improved risk management and assessment.