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Soil pollution by heavy metals is a serious environmental concern globally. Hexavalent (VI) chromium (Cr) is one of the main pollutants causing groundwater and soil heavy metal pollution. Miscanthus sinensis is a C4 perennial grass species with a high level of heavy metal tolerance. This species can effectively remove Cr from soils and maintain desirable biomass production under Cr stress. This research aimed to characterize and compare Cr accumulation in 58 genotypes of M. sinensis and to develop Expressed Sequence Tag–Simple Sequence Repeat (EST-SSR) markers associated with Cr tolerance. The results show that the pattern of translocation of Cr in plants differed among the 58 M. sinensis genotypes following treatment of 200 mg/L of Cr6+; however, in most genotypes, the Cr was primarily accumulated in roots. A total of 43,367 EST-SSRs were identified, and 88 EST-SSR primer pairs corresponding to candidate genes involved in Cr accumulation in M. sinensis were selected for validation. Subsequently, 170 polymorphic loci generated from 24 validated EST-SSRs were used for the population structure and marker–trait association analysis. Based on a general linear model (GLM), a total of 46 associations were identified (p < 0.05), with 14 EST-SSRs markers associated with target traits. Among them, four genes related to ABC transporters, wall-associated receptor kinases, as well as two high-affinity sulfate transporters (ST), were identified under Cr stress (p < 0.05). The results of this study help to accelerate the screening across M. sinensis genotypes for desirable traits under Cr stress and provide a platform for M. sinensis genetic improvement and molecular-marker-assisted breeding. [ABSTRACT FROM AUTHOR]

Biochar has been recognised as an efficacious amendment for the remediation of compound heavy metal contamination in soil. However, the molecular mechanism of biochar-mediated tolerance to compound heavy metal toxicity in cotton is unknown. The objective of this research was to investigate the positive impact of biochar (10 g·kg−1) on reducing damage caused by compound heavy metals (Cd, Pb, and As) in cotton (Gossypium hirsutum L.). The results revealed that biochar reduced Cd concentrations by 24.9 % (roots), and decreased Pb concentrations by 37.1 % (roots) and 59.53 % (stems). Biochar maintained ionic homoeostasis by regulating the expression of metal transporter proteins such as ABC, HIPP, NRAMP3, PCR, and ZIP, and genes related to the carbon skeleton and plasma membrane. Biochar also downregulated genes related to photosynthesis, thereby increasing photosynthesis. Biochar re-established redox homoeostasis in cotton by activating signal transduction, which regulated the activity of the enzymes POD, SOD, and CAT activity; and the expression of related genes. This research revealed the molecular mechanism by which biochar confers resistance to the harmful effects of compound heavy metal toxicity in cotton. The application of biochar as a soil amendment to neutralise the toxicity of compound heavy metals is recommended for cash crop production. • Biochar regulates transporter proteins to reduce Cd and Pb accumulation and maintain ionic homeostasis. • Biochar regulates the expression of genes related to photosynthesis. • Biochar alleviates oxidative stress induced by compound heavy metals in cotton seedlings. • Signal transduction play an important role in biochar-mediated mitigation of compound heavy metal toxicity. [ABSTRACT FROM AUTHOR]