Nickel increases susceptibility of a nickel hyperaccumulator to Turnip mosaic virus

Hyperaccumulated Ni can defend plant tissues against herbivores and pathoge ns. 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. Plan ts of a Ni hyperaccumulator, milk-wort jewelflower (S. polygaloides Gray), and a non-hyperaccumulator, plumed jewelflower (S. insignis Jepson), were g rown 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 th e magnitude of TuMV accumulation (measured by indirect enzyme-linked immuno sorbent assay [ELISA]) or by plant survival. Streptanthus polygaloides plan ts grown on high-Ni soil were more susceptible to TuMV than low-Ni S. polyg aloides at all three phenological stages. All rosette and pre-bolt S. insig nis plants were infected by TuMV, but survival and TuMV accumulation were n ot significantly affected by soil Ni. At flowering, only high-Ni S. polygal oides plants became infected. For S. polygaloides, elevated tissue Ni conce ntrations enhanced TuMV infection instead of defending plants from the viru s. To reduce risks to nearby agricultural crops, future phytoremediation an d phytomining operations using this species should incorporate management p lans to prevent the creation of artificial reservoirs of TuMV inoculum.