Increased Nitrogen Application Alleviates Straighthead Disease by Reducing Dimethylarsinic Acid Accumulation and Promoting Mineral Nutrient Uptake in Rice

Excess dimethylarsinic acid (DMA) induces rice straighthead disease with typical symptoms including spikelet sterility, distorted husks, unfilled grains, and erect panicles. Although nitrogen (N) fertilizer application is a routine agronomic practice, the effect of N addition on DMA accumulation in rice and occurrence of straighthead disease has not been fully understood. Field surveys were initially conducted to examine the relationship between grain N and arsenic (As) accumulation. Subsequently, a pot experiment was carried out to investigate the effect of N application on straighthead morbidity and accumulation of As and mineral elements in grains of susceptible variety Ruanhuayou1179 (RHY) and tolerant species Nanjingxiangzhan (NJXZ) under DMA stress. The surveys revealed a significant negative relation between As versus N, Cu, and Zn in rice grains from As-contaminated paddy soils. The addition of DMA significantly altered the rice phenotypes, As and mineral element accumulation in grains, with notable variations observed among cultivars. Tolerant cultivars accumulated lower levels of total As and DMA in the grains than susceptible ones when injecting DMA into the rhizosphere soils, with the appearance of stable seed setting rate, yield and mineral element levels. In comparison with the routine N dose, extra 20% N addition increased the seed setting rate and grain yield by 27% and 19% for RHY, as well as 15% and 12% for NJXZ under DMA stress, respectively. Similarly, grain DMA contents under extra 20% N addition were 36% (RHY) and 26% (NJXZ) lower than those under DMA treatments. Element analysis displays a mitigative effect of N fertilizer application on the inhibition of mineral element accumulation in grains under DMA stress and unveils a close relationship of seed setting rate associated with Cu and Zn. Increasing N fertilizer alleviates straighthead disease by reducing DMA accumulation and enhancing certain mineral uptake in rice. This study provides valuable insights into using N application as a strategy to reduce As uptake and mitigate rice straighthead disease.