First report of Gnomoniopsis smithogilvyi causing lesions and cankers of sweet chestnut in the United Kingdom

Abstract

In late summer 2016 cankers and shoot dieback were detected on a sweet chestnut (Castanea sativa) tree (Figs. 1-2) during a survey for chestnut blight (Cryphonectria parastica) in southeast England. The tree was part of a two-year-old amenity planting scheme. Samples of the affected shoots were sent to the Tree Health Diagnostic and Advisory Service at Forest Research for examination. Isolations were made from the margin of the lesion and plated onto malt agar amended with 1% streptomycin, and the plates incubated for 4 days at 20°C in the dark. A fungus grew consistently from the affected tissues and growing colonies were transferred to 2% potato dextrose agar (PDA) and incubated further. The fungus formed a white fluffy colony on PDA after seven days ( Fig. 3) and readily produced hyaline, fusoid, obovoid and multi-gutulate conidia which were straight or slightly curved (without appendages) after 14 days. Spore dimensions were 5-7.5 µm x 1.25-2.5 µm. DNA was extracted from mycelium and the ITS region was amplified and sequenced with the primers ITS1 and ITS4. Based on morphological features and ITS sequences the identity of the fungus was confirmed as Gnomoniopsis smithogilvyi (Shuttleworth et al., 2012). The sequences of the ITS showed 100% identity with sequences of G. smithogilvyi deposited in GenBank and a representative sequence was submitted to GenBank (Accession No. KY695232).Pathogenicity tests were done by inoculating six three-year-old sweet chestnut saplings. Following surface sterilisation, a wound was made on the stem 10 cm above soil level using a sterilised 5 mm cork borer. A 5 mm diameter mycelial plug taken from a month-old colony of G. smithogilvyi was inserted into the wound which was covered with moistened cotton and wrapped with paraffin film and then aluminium foil. Six control sweet chestnut saplings were inoculated with sterile agar plugs. Saplings were kept in a growth chamber and maintained at 20°C with a 12 hr photoperiod. After four weeks, necrotic lesions were observed only on the inoculated saplings and the fungus was consistently reisolated from all lesions (Fig. 4). Control saplings, however, were asymptomatic and no G. smithogilvyi was recovered from them. The identity was confirmed by morphology and by sequencing of the ITS region.

Gnomoniopsis chinensis (Gnomoniaceae, Diaporthales), a new fungus causing canker of Chinese chestnut in Hebei Province, China

“…Another example is that Gnomoniopsis daii causes Chinese chestnut rot and Gnomoniopsis smithogilvyi causes European chestnut rot (Crous et al 2012;Jiang and Tian 2019). Interestingly, this study reveals a novel Gnomoniopsis species, G. chinensis, as an opportunistic pathogen causing bark cankers on Chinese chestnut, which is different from Gnomoniopsis smithogilvyi causing both nut rot and bark cankers (Crous et al 2012;Visentin et al 2012;Rai 2013, 2015;Pasche et al 2016;Lewis et al 2017;Trapiello et al 2018).…”

“…Gnomoniopsis smithogilvyi is an important nut rot agent on chestnut nuts, an endophyte in asymptomatic flowers, leaves and stems, and a saprobe on dead burrs and branches (Crous et al 2012;Visentin et al 2012). Moreover, this species has been reported as a severe bark pathogen on Castanea in several countries Rai 2013, 2015;Pasche et al 2016;Lewis et al 2017;Trapiello et al 2018;Lione et al 2019). In China, Gnomoniopsis from rotten Chinese chestnut has proved to be a different species, namely Gnomoniopsis daii (Jiang and Tian 2019).…”

Gnomoniopsis castaneae: An emerging plant pathogen and global threat to chestnut systems

“…Isolations made from lesions observed on a field‐planted sweet chestnut affected by shoot dieback in the United Kingdom consistently produced G. castaneae (Lewis et al, 2017). Pathogenicity trials of seedlings induced necrotic lesions in the treated trees but not in the controls, and the pathogen was never isolated from symptomless tissue.…”

“…The pathogen is, therefore, considered to be host‐genus specific to Castanea species. G. castaneae is now found on a global scale and has been identified in chestnut tissues throughout Europe (Lewis et al, 2017; Pasche, Calmin, et al, 2016; Visentin et al, 2012), Oceania (Shuttleworth et al, 2012), India (Dar & Rai, 2015), the United States (Sakalidis et al, 2019) and Chile (Morales‐Rodriguez et al, 2021). Although considered specific to Castanea species, G. castaneae has also been identified as a leaf endophyte of manna ash (Oleaceae: Fraxinus ornus ; Ibrahim et al, 2017), in association with cankers of European hazelnut (Betulaceae: Corylus avellana ; Linaldeddu et al, 2016) and common box (Buxaceae: Buxus sempervirens ; Şimşek et al, 2019) and present with unknown activity in holm oak (Fagaceae: Quercus ilex ; Shuttleworth et al, 2012).…”

First report of the fungus Gnomoniopsis smithogilvyi causing cankers on sweet chestnut (Castanea sativa) in Ireland

“…Gnomoniopsis smithogilvyi causes cankers on C. sativa hybrids in Spain, and on C. sativa in five European countries (Shuttleworth et al., 2016; Lewis et al., 2017; Lione et al., 2019). It also causes chestnut rot in C. sativa in Australia, France, Italy, New Zealand, Portugal and Switzerland (Visentin et al., 2012; Shuttleworth et al., 2016; Coelho & Gouveia, 2021).…”