Neofusicoccum Parvum, a New Agent of Sequoia Canker and Dieback Identified in Geneva, Switzerland
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Article Neofusicoccum parvum, A New Agent of Sequoia Canker and Dieback Identified in Geneva, Switzerland Martine Haenzi, Bastien Cochard, Romain Chablais, Julien Crovadore and François Lefort * Plants and Pathogens Group, Institute Land Nature Environment, Geneva School of Engineering Architecture and Landscape (HEPIA), HES-SO University of Applied Sciences and Arts Western Switzerland, 150 Route de Presinge, 1254 Jussy, Switzerland; [email protected] (M.H.); [email protected] (B.C.); [email protected] (R.C.); [email protected] (J.C.) * Correspondence: [email protected]; Tel.: +41-22-546-68-27 Abstract: Fungi were isolated in pure cultures from decaying giant sequoias in Geneva (Switzerland). Isolates were genetically identified by ITS rDNA sequencing. Young giant sequoia trees were artifi- cially infected with a pure culture of Botryosphaeria parva. Henle-Koch’s Postulates demonstrated that Botryosphaeria parva was pathogenic to Sequoiadendron giganteum. When analysing the microorganisms associated to canker and dieback symptoms in a giant sequoias (Sequoiadendron giganteum) in Geneva, the fungus Neofusicoccum parvum (Pennycook & Samuels) Crous, Slippers & A.J.L. Phillips, teleo- morph Botryosphaeria parva (Pennycook & Samuels) Crous, Slippers & A.J.L. Phillips, was isolated, whereas such symptoms are commonly associated to Fusicoccum aesculi (teleomorph Botryosphaeria dothidea). These two fungal species belong to the same genus Botryosphaeria of the Botryosphaeriaceae family. Because Neofusicoccum parvum was causing cankers and diebacks in other woody species around the world, we extended the analysis to other trees displaying sequoia dieback symptoms in order to evaluate the involvement of Neofusicoccum parvum in such increasing symptoms in sequoias Citation: Haenzi, M.; Cochard, B.; in Geneva. Dried twigs, trunk, and branch cankers from diseased trees were sampled on several Chablais, R.; Crovadore, J.; Lefort, F. distinct sites. From all samples, isolated fungi in pure cultures showed a phenotype typical of Neofusicoccum parvum, A New Agent of Sequoia Canker and Dieback Botryosphaeriaceae species. Isolates were then genetically identified at the species level. Subse- Identified in Geneva, Switzerland. quently Neofusicoccum parvum was inoculated to young giant sequoia trees, re-isolated in pure culture Forests 2021, 12, 434. https:// from provoked symptoms, and re-identified to fulfil Henle-Koch’s postulates. The identification con- doi.org/10.3390/f12040434 firmed that Neofusicoccum parvum was present on all sites, while Fusicoccum aesculi was retrieved only once alone. The inoculation of Neofusicoccum parvum isolates on young sequoias demonstrated for Academic Editor: Rostislav Zemek the first time that this fungus was able to develop cankers in Sequoiadendron giganteum. Neofusicoccum and Katarína Pastirˇcáková parvum could, therefore, be the major cause for dying of giant sequoias in the Geneva Lake area. Received: 15 February 2021 Keywords: Botryosphaeria parva; Botryosphaeria dothidea; Fusicoccum aesculi; Neofusicoccum parvum; Accepted: 31 March 2021 sequoia canker; sequoia dieback Published: 4 April 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in 1. Introduction published maps and institutional affil- iations. Introduced in the 1850s to Europe, giant sequoia trees (Sequoiadendron giganteum (Lindl.) J. Buchholz, 1939) met a general and genuine craze. The first sequoia trees were also sewed and planted at the same time in Geneva. Some of the still-living trees today date from this period. Most of the 350 giant sequoias, present in the territory of the canton of Geneva, now show symptoms of a disease similar to that caused by the fungal Copyright: © 2021 by the authors. Fusicoccum aesculi Licensee MDPI, Basel, Switzerland. pathogen [1]. The fungus is also known under the name of its teleomorph This article is an open access article Botryosphaeria dothidea (Moug. ex Fr.) Ces. & De Not., [2] (Botryosphaeriaceae). This fungus distributed under the terms and is known to cause the Botryosphaeria canker and white rot on giant sequoia trees of conditions of the Creative Commons Sequoiadendron giganteum, but also on Sequoia sempervirens and incense cedars Calocedrus Attribution (CC BY) license (https:// decurrens in their native region [3–5]. Its pathogenicity was described on S. giganteum and S. creativecommons.org/licenses/by/ sempervirens [4]. Symptoms are known to be more acute on trees established in non-native 4.0/). regions than in the regions of origin. This is especially true in hot and dry climates, where Forests 2021, 12, 434. https://doi.org/10.3390/f12040434 https://www.mdpi.com/journal/forests Forests 2021, 12, x FOR PEER REVIEW 2 of 13 Forests 2021, 12, 434 sempervirens [4]. Symptoms are known to be more acute on trees established in non-native2 of 12 regions than in the regions of origin. This is especially true in hot and dry climates, where the disease usually leads to trees diebacks [6,7]. Botryosphaeria dothidea has been known thefor disease 150 years usually as a mild leads pathogenic to trees diebacks fungus [6 and,7]. Botryosphaeria a common cause dothidea of cankerhas been and known dieback for of 150trees years worldwide as a mild on pathogenic 24 host fungusgenera and[8], aon common which causeit may of cankerprovoke and cankers dieback on of twigs, trees worldwidebranches, and on 24 stems, host generaresulting [8], in on tips which and itbranches may provoke dieback cankers and finally on twigs, plant branches, death. Other and stems,symptoms resulting on some in tips tree and species branches may diebackinclude andfruit finally rot and plant blue death. stains Other[8]. It symptomsis now also onknown some to tree be speciesusually maypresent include as a latent fruit rotendophytic and blue pathogen, stains [8]. which It is now expresses also known its patho- to begenicity usually in presentplant stress as a conditions latent endophytic [8]. Recent pathogen,ly, another which fungus expresses of the same its pathogenicityBotryosphaeri- inaceae plant family, stress conditionsnamed Neofusicoccum [8]. Recently, parvum another (Pennycook fungus of & the Samuels) same Botryosphaeriaceae Crous, Slippers & family,A.J.L. Phillips named [9,10]Neofusicoccum (teleomorph: parvum Botryosphaeria(Pennycook parva & Samuels)(Pennycook Crous, & Samuels) Slippers Crous, & A.J.L. Slip- Phillipspers & [A.J.L.9,10] (teleomorph:Phillips) [10] Botryosphaeriawas found in parvastudies(Pennycook of Botryosphaeria & Samuels) canker Crous, on Slippersgiant se- &quoias A.J.L. in Phillips) Greece [ 10[11].] was These found two in cosmopolitan studies of Botryosphaeria fungal species canker are, however, on giant widespread, sequoias in Greecein a very [11 ].large These range two cosmopolitanof plant hosts, fungal as endophytes species are, as however,well as pathogens widespread, [12–14]. in a very If B. largedothidea range has of long plant been hosts, considered as endophytes a marginally as well as pathogenic pathogens fungus, [12–14]. N. If B.parvum dothidea seemshas longto be beenmore considered aggressive a on marginally important pathogenic crops such fungus, as grapevineN. parvum [15] seemsand olive to be trees more [16]. aggressive On giant onsequoias, important the cropssymptoms such associated as grapevine to an [15 infection] and olive by treesthese [Botryosphaeria16]. On giant species sequoias, include the symptomsthe shrivelling associated of twigs to of an the infection crown, by distribu these Botryosphaeriated in patches,species and the include appearance the shrivelling of cankers ofon twigs twigs, of branches, the crown, and distributed trunks, associated in patches, with and resin the flows. appearance Early trunk of cankers cankers on are twigs, dis- branches,crete in reason and trunks, of the thickness associated of withthe bark resin of flows.sequoias. Early With trunk the progress cankers areof the discrete infection, in reasonthe crown of the displays thickness a ofdiscoloured the bark of foliage sequoias. and With is naturally the progress pruned of the from infection, dead thetwigs crown and displaysbranches. a discolouredIn this study, foliage we have and isolated is naturally Botryosphaeriaceae pruned from dead strains twigs from and diseased branches. giant In thissequoia study, trees we havein different isolated locati Botryosphaeriaceaeons of the Canton strains of Geneva, from diseased in order giantto isolate sequoia and treesaccu- inrately different identify locations the pathogen, of the Canton which of has Geneva, been causing in order these to isolate dieback and and accurately canker symptoms identify theresulting pathogen, in an which increased has been mortality causing of thesethese diebacktrees in andrecent canker years. symptoms resulting in an increased mortality of these trees in recent years. 2. Materials and Methods 2. Materials and Methods 2.1.2.1. Sampled Sampled Trees Trees DiseasedDiseased trees trees were were identified identified by theirby their symptoms symptoms (Figure (Figure1; Figure 1; Figure2). Small 2). dry Small twigs dry peripheraltwigs peripheral to cankers to cankers were sampled were sampled on 11 symptomatic on 11 symptomaticSequoiadendron Sequoiadendron giganteum giganteumtrees in seventrees in different seven different and distant and locations distant locations in Canton in Geneva Canton Switzerland Geneva Switzerland (Figure3). (Figure 3). FigureFigure 1. 1.A A giant giant sequoia sequoia displaying