Nickel-enriched soybean seeds generate plants more resistant to Asian soybean rust

Asian soybean rust (ASR), triggered by Phakopsora pachyrhizi, can cause great yield losses on soybean and nickel (Ni) has potential to control this disease. This study evaluated the effect of using soybean seeds with different Ni contents on ASR control by performing two experiments. In experiment 1, seeds with different Ni contents were obtained by spraying plants three times with solutions containing either 60 or 100 gNi·ha–1. Plants sprayed with water served as the control treatment. In experiment 2, plants originated from seeds obtained in experiment 1 (T1 = 0.9 μgNi·seed–1, T2 = 1.2 μgNi·seed–1, and T3 = 1.6 μgNi·seed–1) were inoculated with P. pachyrhizi at the V4 growth stage. The ASR severity was evaluated 16 days after inoculation (DAI) and the chlorophyll (Chl) a fluorescence parameters at 8 and 16 DAI. The ASR severity decreased by 64 and 47% for treatments T2 and T3, respectively, in comparison to T1 treatment. The photosynthetic apparatus was negatively affected by ASR. The efficiency of the use of light by photosystem II decreased while the energy dissipated by nonregulated form increased in the infected leaflets. There was no significant difference for Chl a fluorescence parameters for T1, T2, and T3 treatments applied to inoculated plants probably due to the biotrophic lifestyle of P. pachyrhizi associated with lower ASR severity. In conclusion, the potential of using seeds with higher Ni content as a tool for ASR integrated management control is highlighted in this study.