Pathogenicity of Ceratocystis fimbriata from New Zealand kūmara on kiwifruit cultivars

Ceratocystis fimbriata was reported in 2010 causing wilt and death of kiwifruit (Actinidia spp.) vines in Brazil, with losses of up to 50% of vines on some orchards. New Zealand is one of the largest producers of kiwifruit in the world, but C. fimbriata has been recorded only on kūmara (Ipomoea batatas) in this country. In this study the pathogenicity of New Zealand isolates of C. fimbriata from kūmara was examined using potted vines of four kiwifruit cultivars. During the trial, none of the vines became visibly diseased, growth rates were not restricted, and discolouration at the inoculation sites on the stem was minimal. In comparison, tests by researchers in Brazil using C. fimbriata isolated from symptomatic kiwifruit resulted in lengthy lesions and death of susceptible kiwifruit seedlings. Sequences of the internal transcribed spacer (ITS) region of rRNA from the New Zealand C. fimbriata isolates were 100% identical to those sequences from C. fimbriata isolates from Ipomoea batatas in GenBank. This study has shown that the New Zealand isolates of C. fimbriata from kūmara are not pathogenic to the kiwifruit cultivars tested, and are a different pathotype to those found on kiwifruit in Brazil.