New threats to endangered Cook’s scurvy grass (Lepidium oleraceum; Brassicaceae): introduced crop viruses and the extent of their spread

ABSTRACT: To date, most research conducted on plant viruses has centred on agricultural systems where viruses greatly reduce economic output. Introduced viruses are globally common and there is a lack of knowledge around how they might affect natural populations. Although it has been suggested that infectious disease may have played an underestimated role in past species extinctions, there is little empirical evidence. Cook’s scurvy grass (Lepidium oleraceum Sparrm. ex G.Forst; Brassicaceae) is a threatened coastal plant endemic to New Zealand. Following the discovery of Turnip mosaic virus (TuMV) in some glasshouse cultivated specimens, we surveyed wild extant Lepidium populations on the Otago coast for TuMV while screening for two other common crop viruses. We show that TuMV is almost ubiquitous among remaining wild L. oleraceum populations on the South Island’s east coast and report the first record of L. oleraceum as a host for both Cauliflower mosaic virus and Turnip yellows virus. The high incidence of virus infection throughout the study populations may make this system one of the first examples of introduced viruses affecting the conservation of a threatened plant species.