Nickel increases susceptibility of a nickel hyperaccumulator to Turnip mosaic virus

Hyperaccumulated Ni can defend plant tissues against herbivores and pathogens. The effectiveness of this defense, however, has not been tested with a viral pathogen. Turnip mosaic virus (TuMV) accumulation was studied in two serpentine species of Streptanthus with different Ni uptake abilities. Plants of a Ni hyperaccumulator, milk-wort jewelflower (S. polygaloides Gray), and a non-hyperaccumulator, plumed jewelflower (S. insignis Jepson), were grown on Ni-amended and unamended soils. Plants were inoculated with TuMV at three different phenological stages: basal rosette, bolting, and flowering. Susceptibility of experimental plants to TuMV was determined either by the magnitude of TuMV accumulation (measured by indirect enzyme-linked immunosorbent assay [ELISA]) or by plant survival. Streptanthus polygaloides plants grown on high-Ni soil were more susceptible to TuMV than low-Ni S. polygaloides at all three phenological stages. All rosette and pre-bolt S. insignis plants were infected by TuMV, but survival and TuMV accumulation were not significantly affected by soil Ni. At flowering, only high-Ni S. polygaloides plants became infected. For S. polygaloides, elevated tissue Ni concentrations enhanced TuMV infection instead of defending plants from the virus. To reduce risks to nearby agricultural crops, future phytoremed. iation and phytomining operations using this species should incorporate management plans to prevent the creation of artificial reservoirs of TuMV inoculum.