Effects of virus infection on growth of the invasive alien Impatiens glandulifera

The absence of fungal or viral diseases of some invasive alien plants partially explains their success. However, for several species this issue has not been studied and no account of such infections are recorded for Impatiens glandulifera, a problematic weed in moist and half-open habitats of central and western Europe. We record for the first time viral infections in plants from different European regions grown in a common garden experiment. The infection was systemic and could be transferred to two species of Chenopodium and five species of Nicotiana, and resulted in the development of local necrotic spots within a week. The symptoms resembled Tobacco Rattle Virus, but this was not confirmed by an ELISA-test. In I. glandulifera the virus led to reduced above-ground biomass. Relative stem biomass and basal diameter were also lower in diseased plants, but therewas no significant differences in plant height and number of main branches. Also virus infection did not affect the following reproductive traits: time to flowering, pollen viability, fruit abortion, seed/ovule ratio, seed number per fruit and individual seed mass. This virus was not transmitted via seed. The potential effects of such viral infections on the population dynamics and biological control of this alien plant are discussed.