Preliminary pathogenicity screening of <i>Verticillium</i> spp. on kiwifruit in New Zealand

Plant-pathogenic Verticillium species have been present in New Zealand for many years, and have been considered minor wilt pathogens of kiwifruit. However, an outbreak of Verticillium nonalfalfae (previously identified as Verticillium alboatrum) causing wilt and death of the kiwifruit cultivar Actinidia chinensis var. chinensis ‘Hort16A’ in Chile has raised questions around the pathogenicity and significance of New Zealand Verticillium species. This study investigated the pathogenicity of New Zealand isolates of Verticillium spp. to ‘Hort16A’. Three isolates of Verticillium dahliae and one of V. alboatrum sensu stricto, previously recovered from kiwifruit in New Zealand, were tested for pathogenicity against ‘Hort16A’ by artificial inoculation of young vines. Disease assessments were carried out monthly. Symptoms observed ranged from minor wilt to vine death. The V. alboatrum isolate appeared the most aggressive. Although there is evidence of some pathogenicity on kiwifruit within this group of isolates from Verticillium species in New Zealand, they appear less aggressive than those recorded in Chile. However, this cannot be confirmed without testing isolates from both countries concurrently under the same conditions.