Pathogenicity of Ceratocystis fimbriata from New Zealand kūmara on kiwifruit cultivars

Abstract

INTRODUCTION Ceratocystis fimbriata is a fungal pathogen that affects a wide variety of plant hosts, in more than 22 families, many of which are of commercial importance. It was first identified on Ipomoea batatas in northeastern USA in 1890 (Halsted 1890), and since then has been widely reported across the world. Ipomoea batatas is known as kūmara in New Zealand and as sweet potato in many other parts of the world, and this distinction is used here. The first record of C. fimbriata in New Zealand was by Kirk (1907) causing black-rot of kūmara in the North Island. In 1947, it was reported on kūmara in Kaitaia and, by 1960, had also been recorded from the Bay of Islands, Helensville, Great Barrier Island, Auckland, Matakana Island (Bay of Plenty) and Gisborne (Slade 1960). Ceratocystis fimbriata is now thought to be a complex of very similar fungal species with numerous different strains. Four phylogenetic clades are now recognised, including the Latin American clade (LAC) (Harrington et al. 2011), to which the Ipomoea strain belongs. Some of the strains of C. fimbriata appear to be host-specific, while others infect a range of hosts, including many of economic importance. Several are potentially different species, others (e.g. C. platani) have previously been raised to species level (Engelbrecht & Harrington 2005). In 2014, C. fimbriata was reported on Ohi'a (Metrosideros polymorpha) in Hawai'i (Keith et al. 2015). It was subsequently shown that the rapid death of Ohi'a was caused by two distinct species within the Ceratocystis fimbriata complex; C. lukuohia and C. huliohia (Barnes et al. 2018). Ceratocystis fimbriata sensu lato is a complex of soil-borne pathogens that cause wilt and cankers on woody plants, e.g. plane trees (Platanus spp.) and Eucalyptus spp. (Zauza et al. 2004; Tsopelas et al. 2017), as well as postharvest rots of storage roots and corms, e.g. taro (Colocasia esculenta) and sweet potato (Halsted & Fairchild 1891; Harrington et al. 2005). Woody hosts tend to be invaded through wounds, although the pathogen may also move between hosts through root grafts and may also directly infect roots (Harrington 2013). In sweet potato/kūmara, infection may be through contaminated planting material (slips) but the pathogen is more often introduced directly through damaged roots, lenticels or wounds (Lewthwaite et al. 2011). In South America, C. fimbriata is a native pathogen with a wide host range (Harrington et al. 2011; Ferreira et al. 2013). In 2010, it was reported causing wilt and death of kiwifruit (Actinidia spp.) vines in Rio Grande do Sul, Brazil (Sonego et al. 2010; Ferreira et al. 2013; Piveta et al. 2016). Subsequent phylogenetic analyses showed that the kiwifruit isolates belonged to three lineages within the LAC, suggesting three populations of C. fimbriata genotypes on kiwifruit (Ferreira et al. 2017). All kiwifruit isolates tested by Piveta et al. (2016) were pathogenic to kiwifruit and isolates from different ITS haplotypes did not differ widely in aggressiveness. Symptoms of ceratocystis wi...

Resistance of kiwifruit cultivars to ceratocystis wilt: An approach considering the genetic diversity and variation in aggressiveness of the pathogen

“…For instance, C. fimbriata has been reported on taro, sweet potato, pomegranate, eucalyptus, and mango in Yunnan Province in China, one of the kiwifruit-growing areas and also where the Actinidia Biodiversity Centre is located (Huang, 2016), representing a serious threat to one of the greatest kiwifruit germplasm collections in the world. In New Zealand C. fimbriata has been reported on sweet potato, but the strain found in that area is not able to infect kiwifruit (Tyson et al, 2020).…”

Potential Threat of Ceratocystis lukuohia on kiwifruit crop

“…The intraspeci c and interspeci c variability in the Ceratocystis species is related to host speciation, aggressiveness variation, and speci c interactions with certain cultivars or clones (Cowger et al, 2000;Oliveira et al, 2020). Some species and/or isolates are related to single hosts or geographic regions, while others infect a wide range of hosts (Thorpe et al, 2005;Tyson et al, 2020). Since the rst report of Ceratocystis wilt on kiwifruit vines (Sonego et al, 2010), investigation of pathogenicity of Ceratocystis spp.…”

“…found in other countries, mainly those occurring in kiwifruit-producing countries, has become important for implementing biosecurity measures to prevent the introduction of pathogenic isolates in kiwifruit orchards. Tyson et al (2020) showed that New Zealand isolates of C. mbriata from sweet potato (kumara) are not pathogenic to a range of kiwifruit cultivars (Hayward, Gold3, Gold14, Bounty). In addition, the sweet potato isolates were non-pathogenic on mango (Mangifera indica), yam (Dioscoera spp.…”

Ceratocystis fimbriata - Actinidia spp. pathosystem: mechanical dispersal, disease control and pathogenicity of isolates from different hosts

“…The complex Ceratocystis fimbriata sensu lato (s.l.) is formed by a group of species with a high genetic variability, with some species or isolates related to single hosts or geographic regions, while others infect a wide range of hosts (THORPE et al, 2005;TYSON et al, 2020). Furthermore, the C. fimbriata intraspecific variability is related to aggressiveness variation and specific interaction may occur with particular cultivar or clone (COWGER et al, 2000;.…”

“…The complex Ceratocystis fimbriata sensu lato (s.l.) is formed by a group of very similar fungi and with a high number of isolates widely distributed geographically, some species are related to single hosts or geographic regions, while others infect a range of hosts (Thorpe et al 2004, Tyson et al 2020. The wide host range of C. fimbriata (s.l.)…”