Verticillium wilt on the invasive plant species, Ailanthus altissima, has been reported in Europe and USA. Symptoms of the disease in northeastern Spain were first observed in 2007, and it has progressively expanded within this region thereafter. In this work, ninety-two Verticillium isolates were recovered from diseased Ailanthus trees in four riparian-forested sites in the Girona Province of northeastern Spain. Identification of Verticillium field isolates to species was based on morphological traits and species-specific PCR assays. All isolates were identified as V. dahliae, which was consistently recovered from all surveyed diseased Ailanthus stands, supporting its strong association with Ailanthus decline in the region. The use of race-specific molecular markers revealed the presence of races 1 and 2 in V. dahliae populations from Ailanthus in Spain; however, only a single race was present at each of the sampled locations. Furthermore, PCR-based assays designed to differentiate defoliating and nondefoliating V. dahliae pathotypes indicated the exclusive presence of the nondefoliating pathotype in V. dahliae populations from Ailanthus in the region. All isolates were pathogenic and virulent on Ailanthus seedlings, severe wilting, defoliation and occasional plant death were observed 90 days after inoculation regardless of the race. The race and pathotype structure of the V. dahliae population from Ailanthus had not been investigated previously. These findings confirm the widespread occurrence of Verticillium wilt caused by V. dahliae in Ailanthus in Europe and provide new insights into the population structure of this pathogen on natural stands of this invasive plant species.
Carol et al. (Fri,) studied this question.
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