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Rice straighthead disease substantially reduces crop yield, posing a significant threat to global food security. Dimethylarsinic acid (DMA) is the causal agent of straighthead disease and is highly toxic to the reproductive tissue of rice. However, the precise physiological mechanism underlying DMA toxicity remains unknown. In this study, six rice varieties with varying susceptibility to straighthead were utilized to investigate the growth performance and element distribution in rice panicles under DMA stress through pot experiments, as well as to explore the physiological response to DMA using transcriptomic methods. The findings demonstrate significant variations in both DMA accumulation and straighthead sensitivity among cultivars. The susceptible varieties exhibited higher DMA accumulation indices and displayed typical symptoms of straighthead disease, including erect panicles, deformed rachides and husks, and reduced seed setting rate and grain yield when compared to the resistant varieties. Moreover, DMA addition promoted mineral nutrients to accumulate in rachides and husks but less in grains. DMA showed preferential accumulation in rice grains with a distribution pattern similar to that of Copper (Cu) and zinc (Zn) within the panicle. Transcriptome analyses underscored the substantial impact of DMA on gene expression related to mineral metabolism. Notably, DMA addition significantly up‐regulated the expression of pectin methylesterase, pectin lyase, polygalacturonase, and exogalacturonase genes in Nanjingxiangzhan, while these genes were down‐regulated or weakly expressed in Ruanhuayou 1179. The alteration of pectin metabolic pathways induced by DMA may lead to abnormality of cell wall assembly and modification, thereby resulting in deformed rice panicles. [ABSTRACT FROM AUTHOR]

Roxarsone (ROX), an organoarsenic feed additive, and its metabolites, can be present in animal manure used to fertilize rice. Rice is prone to absorb arsenic, and is subject to straighthead disorder, which reduces rice yield and is linked with organic arsenic compounds. This study aims to elucidate how soil property affect arsenic accumulation in rice plants fertilized with chicken manure containing ROX metabolites. Manures of chickens fed without or with ROX, designated as control manure and ROX treated manure (ROXCM), respectively, were applied in eight paddy soils of different origins, to investigate the assimilation of arsenic species in rice plants. The results show that inorganic arsenic (arsenate and arsenite), monomethylarsonic acid and dimethylarsinic acid (DMA) were detected in all brown rice and husk, trace tetramethylarsonium and trimethylarsine oxide were occasionally found in these both parts, whereas all these arsenic species were determined in straw, irrespective of manure type. ROXCM application specifically and significantly increased brown rice DMA (P = 0.002), which remarkably enhanced the risk of straighthead disease in rice. Although soil total As impacted grain biomass, soil free-iron oxides and pH dominated arsenic accumulation by rice plants. The significantly increased grain DMA suggests manure bearing ROX metabolites is not suitable to be used in soils with abundant free-iron oxides and/or high pH, if straighthead disorder is to be avoided in rice. • ROX metabolites significantly enhance grain DMA and thus raise grain total As. • ROX metabolites do not affect total As and As species in rice straw and husk. • Soil free-Fe oxides or pH dominates uptake of ROX metabolites by rice plant. • Animal manure with ROX metabolites should not be used in soils with high Fe or pH. [ABSTRACT FROM AUTHOR]

Roxarsone (ROX), a widely used feed additive, occurs as itself and its metabolites in animal manure. Rice is prone to accumulate As than other staple food. Four diets with 0, 40, 80 and 120 mg ROX kg − 1 were fed in chickens, and four chicken manures (CMs) were collected to fertilize rice plants in a soil culture experiment. Linear regression analysis shows that the slopes of As species including 4-hydroxy-phenylarsonic acid, As(V), As(III), monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) in CM versus dietary ROX were 0.033, 0.314, 0.033, 0.054 and 0.138, respectively. Both As(III) and DMA were determined in all rice grains, and As(III), As(V), MMA and DMA in rice hull, but detectable As forms in rice straws and soils increased with increasing ROX dose. Grain As(III) was unrelated to ROX dose but exceeded the Chinese rice As limit (0.15 mg As(III) kg − 1 ). Dietary ROX enhanced straw As(III) mostly, with the slope of 0.020, followed by hull DMA (0.006) and grain DMA (0.002). The slopes of soil As(V) and As(III) were 0.003 and 0.001. This is the first report illustrating the quantitative delivery of ROX via food chain, which helps to evaluate health and environmental risks caused by ROX use in animal production. [ABSTRACT FROM AUTHOR]