Nickel Increases Susceptibility of a Nickel Hyperaccumulator to Turnip mosaic virus

Abstract

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.

Nickel and zinc hyperaccumulation by Alyssum murale and Thlaspi caerulescens (Brassicaceae) do not enhance survival and whole‐plant growth under drought stress

“…Martens & Boyd 1994;Pollard & Baker 1997;Pollard, Dandridge & Jhee 2000;Davis & Boyd 2000), limit infection by pathogenic fungi (Ghaderian, Lyon & Baker 2000), and enrich the soils under their canopy with higher concentrations of toxic metals (Boyd & Jaffré 2001). In contrast, however, Ni-hyperaccumulation increased the susceptibility of Streptanthus polygaloides (Gray) to a mosaic virus (Davis, Murphy & Boyd 2001).…”

Soil calcium and plant disease in serpentine ecosystems: a test of the pathogen refuge hypothesis

“…The handful of studies that have considered plant pathogens in serpentine ecosystems have all focused on hyperaccumulators, plants that have unusually high tissue concentrations of certain selectively absorbed heavy metals (e.g., nickel, selenium). While a few studies have documented reduced rates of infection in hyperaccumulators (Boyd et al 1994;Davis et al 2001;Hanson et al 2003), this defensive strategy is taxonomically rare and characteristic of only a fraction of serpentineassociated plants (Brooks 1998). Exposure to low soil calcium concentrations is a condition experienced by all serpentine Xora, so eVects of calcium availability on interactions with pathogens should be pervasive among the nonhyperaccumulating members of these plant communities.…”

Nickel defends the South African hyperaccumulator Senecio coronatus (Asteraceae) against Helix aspersa (Mollusca: Pulmonidae)

“…However, some herbivores or plant parasites are able to attack metal hyperaccumulators despite their elemental defence. These include an aphid ), a mirid bug (Schwartz & Wall 2001), a parasitic plant , and a virus (Davis et al 2001). Thus, it is clear that elemental defences, like other modes of plant defence, can be circumvented.…”

“…In other studies of hyperaccumulator plant defence, plants are grown on high-and low-metal substrates (e.g., Pollard & Baker 1997;Ghaderian et al 2000;Davis et al 2001) and/or a closely-related species is used for comparative purposes (e.g., Davis et al 2001). Senecio coronatus (Thunberg) Harvey (Asteraceae) is a grassland herb of southern Africa (Hilliard 1977) found on both ultramafic and non-ultramafic soils.…”