Pathogenicity and relative virulence of seven Phytophthora species on kiwifruit

Abstract

The role of Phytophthora species in the development of root rot in kiwifruit was investigated. Seven species were isolated from soil samples collected from the base of unhealthy kiwifruit vines in six orchards in the Auckland region, New Zealand, using a soil baiting technique. The species were identified as Phytophthora cinnamomi, P. citricola, P. cryptogea, P. gonapodyides, P. megasperma, P. sterile A and P. sterile B. With the exception of P. megasperma, all species were pathogenic against 9-month-old kiwifruit plants in glasshouse tests. In particular, P. cryptogea and P. cinnamomi were highly virulent causing extensive rotting of the fine fibrous roots of rootstocks of cultivars Hayward and Bruno. Cultivar Hayward was more susceptible to infection than Bruno by four of the six pathogenic species.

Keywords:

• ‘Bruno’
• ‘Hayward’
• kiwifruit
• Phytophthora spp.
• P. cryptogea
• root rot