Host range, biological variation, and phylogenetic diversity of Eutypa lata in California

Determining the Main Infection Courts in Sweet Cherry Trees of the Canker Pathogens Calosphaeria pulchella, Cytospora sorbicola, and Eutypa lata

The major fungal canker pathogens causing branch dieback of sweet cherry trees in California include Calosphaeria pulchella, Cytospora sorbicola, and Eutypa lata. These pathogens have long been known to infect cherry trees mainly through pruning wounds. However, recent field observations revealed numerous shoots and fruiting spurs exhibiting dieback symptoms with no apparent pruning wounds or mechanical injuries. Accordingly, this study was conducted to assess the incidence of the three pathogens in symptomatic terminal shoots and dying fruiting spurs, in addition to the wood below pruning wounds in branches. Surveys were conducted in five sweet cherry orchards across three counties in California. We also investigated the possibility that leaf scars, bud scars, and wounds resulting from fruit picking could serve as infection courts for Cal. pulchella, Cyt. sorbicola, and E. lata by means of artificial inoculations in the field. Orchard surveys revealed that Cal. pulchella had the highest pathogen incidence below pruning wounds in branch samples, followed by Cyt. sorbicola and E. lata. Among terminal shoots with dieback symptoms and dying fruiting spurs, Cyt. sorbicola was the most prevalent, followed by Cal. pulchella. Results from field inoculations indicated that fruit-picking wounds could serve as important infection courts for Cal. pulchella, Cyt. sorbicola, and E. lata, with average pathogen recovery of 41.5, 63, and 36.2%, respectively. Results also indicated that leaf and bud scars could serve as an entry site for Cyt. sorbicola, although recovery was relatively low. The present study is the first to identify harvest-induced wounds on fruiting spurs of sweet cherry as an important infection court of Cal. pulchella, Cyt. sorbicola, and E. lata.

Fungal Trunk Diseases Causing Decline of Apricot and Plum Trees in the Czech Republic

Fungal trunk diseases (FTDs) have been a significant threat to the global stone fruit industry. FTDs are caused by a consortium of wood-decaying fungi. These fungi colonize woody tissues, causing cankers, dieback, and other decline-related symptoms in host plants. In this study, a detailed screening of the fungal microbiota associated with the decline of stone fruit trees in the Czech Republic was performed. The wood fragments of plum and apricot trees showing symptoms of FTDs were subjected to fungal isolation. The partial internal transcribed spacer region, partial beta-tubulin, and translation elongation factor 1-α genes were amplified from genomic DNA extracted from fungal cultures. All isolates were classified, and the taxonomic placement of pathogenic strains was illustrated in phylogenetic trees. The most abundant pathogenic genus was Dactylonectria (31%), followed by Biscogniauxia (13%), Thelonectria (10%), Eutypa (9%), Dothiorella (7%), Diplodia (6%), and Diaporthe (6%). The most frequent endophytic genus was Aposphaeria (17%). The pathogenicity of six fungal species (Cadophora daguensis, Collophorina africana, Cytospora sorbicola, Dothiorella sarmentorum, Eutypa lata, and E. petrakii var. petrakii) to four Prunus spp. was evaluated, and Koch's postulates were fulfilled. All tested isolates caused lesions on at least one Prunus sp. The most aggressive species was E. lata, which caused the largest lesions on all four tested Prunus spp., followed by E. petrakii var. petrakii and D. sarmentorum. Japanese plum (Prunus salicina) and almond (P. amygdalus) were the most susceptible hosts, while apricot (P. armeniaca) was the least susceptible host in the pathogenicity trial.

Comparative Pangenomic Insights into the Distinct Evolution of Virulence Factors Among Grapevine Trunk Pathogens

The permanent organs of grapevines (Vitis vinifera L.), like those of other woody perennials, are colonized by various unrelated pathogenic ascomycete fungi secreting cell wall-degrading enzymes and phytotoxic secondary metabolites that contribute to host damage and disease symptoms. Trunk pathogens differ in the symptoms they induce and the extent and speed of damage. Isolates of the same species often display a wide virulence range, even within the same vineyard. This study focuses on Eutypa lata, Neofusicoccum parvum, and Phaeoacremonium minimum, causal agents of Eutypa dieback, Botryosphaeria dieback, and Esca, respectively. We sequenced 50 isolates from viticulture regions worldwide and built nucleotide-level, reference-free pangenomes for each species. Through examination of genomic diversity and pangenome structure, we analyzed intraspecific conservation and variability of putative virulence factors, focusing on functions under positive selection and recent gene family dynamics of contraction and expansion. Our findings reveal contrasting distributions of putative virulence factors in the core, dispensable, and private genomes of each pangenome. For example, carbohydrate active enzymes (CAZymes) were prevalent in the core genomes of each pangenome, whereas biosynthetic gene clusters were prevalent in the dispensable genomes of E. lata and P. minimum. The dispensable fractions were also enriched in Gypsy transposable elements and virulence factors under positive selection (polyketide synthase genes in E. lata and P. minimum, glycosyltransferases in N. parvum). Our findings underscore the complexity of the genomic architecture in each species and provide insights into their adaptive strategies, enhancing our understanding of the underlying mechanisms of virulence. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Effects of Temperature on Spore Germination and Mycelial Growth of Calosphaeria pulchella, Cytospora sorbicola, and Eutypa lata Isolates Associated with Sweet Cherry Canker Diseases

Although fungal canker diseases constitute a limiting factor to orchard productivity and longevity, little is known about the effects of temperature on spore germination and mycelial growth of the fungal causal agents. Accordingly, the germination of spores and colony growth of Calosphaeria pulchella, Cytospora sorbicola, and Eutypa lata were evaluated after incubation on 2% water agar and 4% potato dextrose agar, respectively, at 5, 10, 15, 20, 25, 30, 35, and 40°C. Temperature optima for spore germination and mycelial growth were derived from nonlinear models fitted to germination rates and colony diameter data. The optimal temperatures for spore germination of Cal. pulchella were 28.5°C for ascospores and 29.2°C for conidia. The optimal temperatures for Cyt. sorbicola conidia and E. lata ascospore germination were 25.8 and 23.1°C, respectively. The germination of ascospores and conidia of Cal. pulchella at temperatures below 15°C required an incubation time of at least 72 h. Ascospores of E. lata and conidia of Cyt. sorbicola germinated at 10°C after 36 h. The optimal temperature for colony growth of Cal. pulchella was 24.6°C, whereas it was 21.7°C for both Cyt. sorbicola and E. lata. Our study indicates that temperature requirements for basic biological functions are higher for Cal. pulchella than for Cyt. sorbicola and E. lata. The overall higher temperatures of California relative to other cherry-producing regions in the United States or worldwide could explain the prevalence of Calosphaeria canker in the state. Conversely, Cyt. sorbicola and E. lata appear better adapted to cooler temperatures.

Seasonal Susceptibility of Sweet Cherry Pruning Wounds to Calosphaeria pulchella, Cytospora sorbicola, and Eutypa lata

Fungal canker pathogens commonly infect trees at pruning wounds leading to branch dieback and loss of productivity in sweet cherry orchards. However, the seasonal susceptibility of sweet cherry pruning wounds to Calosphaeria pulchella, Cytospora sorbicola, and Eutypa lata is not well understood. This study compared the susceptibility of sweet cherry pruning wounds made during the dormant season (January) and the postharvest season (late May to June) to infection by main canker pathogens in California. Field trials were conducted in three cherry orchards and trees were pruned at the different periods over 2 years. Fresh pruning wounds were inoculated with spores of each pathogen, and pathogen recovery was assessed through microbiological isolations at 3 to 4 months after inoculations. Pruning wounds made in late May and June resulted in significantly higher infection by Cal. pulchella compared to pruning wounds made in January. Pruning wounds made during both seasons were generally equally susceptible to Cyt. sorbicola and E. lata infections. However, there was one orchard where dormant pruning wounds were more susceptible to infection by E. lata and there was one particularly cold winter where Cyt. sorbicola did not infect pruning wounds. Overall, our findings suggest that Cal. pulchella infections of cherry pruning wounds are more likely to occur during periods of warm temperatures such as late spring and early summer. However, infections by Cyt. sorbicola and E. lata can occur year-round if inoculum is present and if winter temperatures are not abnormally low for California. Finally, our results suggest that the emergence of Cal. pulchella as a major canker pathogen of sweet cherry in California may be the result of a shift from dormant to after-harvest pruning of sweet cherry trees.

Diversity, morphology, and molecular phylogeny of Diatrypaceae from southern China

During an investigation of Diatrypaceae from southern China, 10 xylariales-like taxa have been collected. Morphological and multi-gene analyses confirmed that these taxa reside in Diatrypaceae and represent eight novel taxa and two new records belonging to six genera (viz., Allocryptovalsa, Diatrype, Diatrypella, Paraeutypella, Peroneutypa, and Vasilyeva gen. nov.). Vasilyeva gen. nov. was proposed to accommodate Vasilyeva cinnamomi sp. nov. Among the other collections, seven new species were introduced (viz., Diatrype camelliae-japonicae sp. nov., Diatrype rubi sp. nov., Diatrypella guiyangensis sp. nov., Diatrypella fatsiae-japonicae sp. nov., Paraeutypella subguizhouensis sp. nov., Peroneutypa hainanensis sp. nov., and Peroneutypa qianensis sp. nov.), while two were reported as new records from China (Allocryptovalsa rabenhorstii and Diatrype enteroxantha). For Diatrypaceae, the traditional taxonomic approach based on morphology may not be applicable.

Taxonomic and phylogenetic contributions to Diatrypaceae from southeastern Tibet in China

In this study, we investigated the diversity of diatrypaceous fungi from southeastern Tibet in China. The phylogenetic analyses were carried out based on ITS and β-tubulin sequences of 75 taxa of Diatrypaceae from around the world. Based on a combination of morphological features and molecular evidence, a new genus—Alloeutypa, with three new species—A. milinensis, Diatrype linzhiensis, and Eutypella motuoensis, and a new combination—A. flavovirens, were revealed by the materials in China. Alloeutypa is characterized by stromatal interior olivaceous buff, stromata producing well-developed discrete, and ascospores allantoid, subhyaline. These characteristics separate the new genus from the similar genus Eutypa. Comprehensive morphological descriptions, illustrations, and a phylogenetic tree to show the placement of new taxa are provided. All novelties described herein are morphologically illustrated and phylogeny investigated to better integrate taxa into the higher taxonomic framework and infer their phylogenetic relationships as well as establish new genera and species. Our results indicate that the diatrypaceous fungi harbor higher species diversity in China.

Fungal Grapevine Trunk Diseases in Romanian Vineyards in the Context of the International Situation

Vitis vinifera, known as the common grape vine, represents one of the most important fruit crops in the world. Romania is a wine-producing country with a rich and long tradition in viticulture. In the last decade, increasing reports of damage caused by grapevine trunk diseases (GTDs) have raised concerns in all wine producing countries. Up to now, no study was performed regarding the GTDs situation in Romania, an important grapevine grower in Europe. In this study, we aim, after a comprehensive presentation of the fungal GTDs worldwide, to review the scientific information related to these diseases in Romania in order to open a national platform in an international framework. In order to achieve this, we consulted over 500 references from different scientific databases and cited 309 of them. Our review concludes that, in Romania, there is little amount of available literature on this matter. Three out of six fungal GTDs are reported and well documented in all of the Romanian viticultural zones (except for viticultural zone 4). These are Eutypa dieback, Phomopsis dieback, and Esca disease. Of the fungal pathogens considered responsible Eutypa lata, Phomopsis viticola and Stereum hirsutum are the most studied and well documented in Romania. Management measures are quite limited, and they mostly include preventive measures to stop the GTDs spread and the removal of affected grapevines.

The road to molecular identification and detection of fungal grapevine trunk diseases

Grapevine is regarded as a highly profitable culture, being well spread worldwide and mostly directed to the wine-producing industry. Practices to maintain the vineyard in healthy conditions are tenuous and are exacerbated due to abiotic and biotic stresses, where fungal grapevine trunk diseases (GTDs) play a major role. The abolishment of chemical treatments and the intensification of several management practices led to an uprise in GTD outbreaks. Symptomatology of GTDs is very similar among diseases, leading to underdevelopment of the vines and death in extreme scenarios. Disease progression is widely affected by biotic and abiotic factors, and the prevalence of the pathogens varies with country and region. In this review, the state-of-the-art regarding identification and detection of GTDs is vastly analyzed. Methods and protocols used for the identification of GTDs, which are currently rather limited, are highlighted. The main conclusion is the utter need for the development of new technologies to easily and precisely detect the presence of the pathogens related to GTDs, allowing to readily take phytosanitary measures and/or proceed to plant removal in order to establish better vineyard management practices. Moreover, new practices and methods of detection, identification, and quantification of infectious material would allow imposing greater control on nurseries and plant exportation, limiting the movement of infected vines and thus avoiding the propagation of fungal inoculum throughout wine regions.

Comparative Profiling of Wood Canker Pathogens from Spore Traps and Symptomatic Plant Samples Within California Almond and Walnut Orchards

Fungi causing wood canker diseases are major factors limiting productivity and longevity of almond and walnut orchards. The goal of this study was to compare pathogen profiles from spore traps with those of plant samples collected from symptomatic almond and walnut trees and assess if profiles could be influenced by orchard type and age, rainfall amount and frequency, and/or neighboring trees. Three almond orchards and one walnut orchard with different characteristics were selected for this study. Fungal inoculum was captured weekly from nine trees per orchard using a passive spore-trapping device, during a 30-week period in the rainy season (October to April) and for two consecutive years. Fungal taxa identified from spore traps were compared with a collection of fungal isolates obtained from 61 symptomatic wood samples collected from the orchards. Using a culture-dependent approach coupled with molecular identification, we identified 18 known pathogenic species from 10 fungal genera (Ceratocystis destructans, Collophorina hispanica, Cytospora eucalypti, Diaporthe ampelina, Diaporthe chamaeropis/rhusicola, Diaporthe eres, Diaporthe novem, Diplodia corticola, Diplodia mutila, Diplodia seriata, Dothiorella iberica, Dothiorella sarmentorum, Dothiorella viticola, Eutypa lata, Neofusicoccum mediterraneum, Neofusicoccum parvum, Neoscytalidium dimidiatum, and Pleurostoma richardsiae), plus two unidentified Cytospora and Diaporthe species. However, only four species were identified with both methods (Diplodia mutila, Diplodia seriata, Dothiorella Iberica, and E. lata), albeit not consistently across orchards. Our results demonstrate a clear disparity between the two diagnostic methods and caution against using passive spore traps to predict disease risks. In particular, the spore trap approach failed to capture: insect-vectored pathogens such as Ceratocystis destructans that were often recovered from almond trunk and scaffold; Diaporthe chamaeropis/rhusicola commonly isolated from wood samples likely because Diaporthe species have a spatially restricted dispersal mechanism, as spores are exuded in a cirrus; and pathogenic species with low incidence in wood samples such as P. richardsiae and Collophorina hispanica. We propose that orchard inoculum is composed of both endemic taxa that are characterized by frequent and repeated trapping events from the same trees and isolated from plant samples, as well as immigrant taxa characterized by rare trapping events. We hypothesize that host type, orchard age, precipitation, and alternative hosts at the periphery of orchards are factors that could affect pathogen profile. We discuss the limitations and benefits of our methodology and experimental design to develop guidelines and prediction tools for fungal wood canker diseases in California orchards.

A Panoramic View on Grapevine Trunk Diseases Threats: Case of Eutypa Dieback, Botryosphaeria Dieback, and Esca Disease

Grapevine trunk diseases (GTD) are currently one of the most devastating and challenging diseases in viticulture, leading to considerable yield losses and a remarkable decline in grapevine quality. The identification of the causal agents is the cornerstone of an efficient approach to fighting against fungal diseases in a sustainable, non-chemical manner. This review attempts to describe and expose the symptoms of each pathology related to GTD, the modes of transmission, and the harmfulness of recently reported agents. Special attention was given to new diagnostic tests and technologies, grapevine defense mechanisms, molecular mechanisms of endophytes fungal colonization, and management strategies used to control these threats. The present extended review is, therefore, an updated state-of-the-art report on the progress in the management of vineyards.

Morpho-molecular characterisation of Arecophila, with A. australis and A. clypeata sp. nov. and A. miscanthi comb. nov

Three arecophila-like fungal samples were collected on dead culms of gramineous plants in China. Morphological studies of our new collections and the herbarium specimen of Arecophila gulubiicola (generic type) were conducted and the morphological affinity of our new collections with Arecophila was confirmed. Maximum likelihood and Bayesian analyses using combined ITS, LSU, rpb2 and β-tubulin data from our collections revealed the phylogeny of Cainiaceae. The monospecific genus Alishanica (type species Al. miscanthi), which had been accepted in Cainiaceae, is revisited and synonymised under Arecophila. Based on morphology and phylogeny, Arecophila australis sp. nov. and A. clypeata sp. nov. are introduced as new species, while A. miscanthi is a new record for China. All the new collections are illustrated and described.

Lignans Extract from Knotwood of Norway Spruce—A Possible New Weapon against GTDs

Grapevine trunk diseases (GTDs) pose a major threat to the wine industry worldwide. Currently, efficient biological methods or chemical compounds are not available for the treatment of infected grapevines. In the present study, we used an extract from the knotwood of spruce trees as a biological control against GTDs. Our in vitro trial was focused on the antifungal effects of the extract against the most common GTD pathogens—Cadophora luteo-olivacea, Dactylonectria torresensis, Diaporthe ampelina, Diaporthe bohemiae, Diplodia seriata, Eutypa lata, and Phaeoacremonium minimum. Our in vitro trial revealed a high antifungal effect of the extract against all tested fungi. The inhibition rates varied among the different species from 30% to 100% using 1 mg·mL⁻¹ extract. Subsequently, the efficiency of the extract was supported by an in planta experiment. Commercial grafts of Vitis vinifera were treated with the extract and planted. The total genomic DNA of grapevines was extracted 10 days and 180 days after the treatment. The fungal microbial diversities of the treated/untreated plants were compared using high-throughput amplicon sequencing (HTAS). Treated plants showed 76.9% lower relative abundance of the genus Diaporthe and 70% lower relative abundance of the genus Phaeoacremonium 10 days after treatment. A similar scenario was observed for the genus Cadophora 180 days after treatment, where treated plants showed 76% lower relative abundance of this genus compared with untreated grapevines.

Fungal canker agents in apple production hubs of Iran

To identify apple canker casual agents and evaluate their pathogenicity and virulence in apple production hubs including West Azarbaijan, Isfahan and Tehran provinces; samples were collected from symptomatic apple trees. Pathogenic isolates on the detached branches were identified as Cytospora cincta, Diplodia bulgarica, Neoscytalidium dimidiatum and Eutypa cf. lata. E. cf. lata was reported as a potential apple canker causal agent in Iran for the first time based on the pathogenicity test on the detached branches, whereas it caused no canker symptoms in apple trees until 6 months after inoculation. Currently, E. cf. lata seems to be adapted to a single city. C. cincta, D. bulgarica and N. dimidiatum caused canker symptoms in apple trees. “C. cincta” and also “C. cincta and N. dimidiatum” were the most widespread and aggressive apple canker species, respectively, associated with apple canker in Iran. Therefore, they are considered to be the main threat to apple production in Iran and should be carefully monitored. Disease progress curve, area under the disease progress curve and optimum temperatures were determined for mentioned species. It is concluded that the establishment of each species occurs in appropriate areas and times in terms of the optimum temperature for their growth.

The Hidden Diversity of Diatrypaceous Fungi in China

In this study, we investigated the diversity of diatrypaceous fungi from six regions in China based on morpho-molecular analyses of combined ITS and tub2 gene regions. We accept 23 genera in Diatrypaceae with 18 genera involved in the phylogram, and the other five genera are lacking living materials with sequences data. Eleven species included in four genera (viz. Allocryptovalsa, Diatrype, Diatrypella, and Eutypella) have been isolated from seven host species, of which nine novel species (viz. Allocryptovalsa castaneae, A. castaneicola, Diatrype betulae, D. castaneicola, D. quercicola, Diatrypella betulae, Da. betulicola, Da. hubeiensis, and Da. shennongensis), a known species of Diatrypella favacea, and a new record of Eutypella citricola from the host genus Morus are included. Current results show the high diversity of Diatrypaceae which are wood-inhabiting fungi in China.

Fungal Pathogens Associated With Canker Diseases of Almond in California

Almond canker diseases are destructive and can reduce the yield as well as the lifespan of almond orchards. These diseases may affect the trunk and branches of both young and mature trees and can result in tree death soon after orchard establishment in severe cases. Between 2015 and 2018, 70 almond orchards were visited throughout the Central Valley of California upon requests from farm advisors for canker disease diagnosis. Two major canker diseases were identified, including Botryosphaeriaceae cankers and Ceratocystis canker. In addition, five less prevalent canker diseases were identified, including Cytospora, Eutypa, Diaporthe, Collophorina, and Pallidophorina canker. Seventy-four fungal isolates were selected for multilocus phylogenetic analyses of internal transcribed spacer region ITS1-5.8S-ITS2 and part of the translation elongation factor 1-α, β-tubulin, and glyceraldehyde 3-phosphate dehydrogenase gene sequences; 27 species were identified, including 12 Botryosphaeriaceae species, Ceratocystis destructans, five Cytospora species, Collophorina hispanica, four Diaporthe species, two Diatrype species, Eutypa lata, and Pallidophorina paarla. The most frequently isolated species were Ceratocystis destructans, Neoscytalidium dimidiatum, and Cytospora californica. Pathogenicity experiments on almond cultivar Nonpareil revealed that Neofusicoccum parvum, Neofusicoccum arbuti, and Neofusicoccum mediterraneum were the most virulent. Botryosphaeriaceae cankers were predominantly found in young orchards and symptoms were most prevalent on the trunks of trees. Ceratocystis canker was most commonly found in mature orchards and associated with symptoms found on trunks or large scaffold branches. This study provides a thorough examination of the diversity and pathogenicity of fungal pathogens associated with branch and trunk cankers of almond in California.

Eutypella parasitica and Other Frequently Isolated Fungi in Wood of Dead Branches of Young Sycamore Maple (Acer pseudoplatanus) in Slovenia

Eutypella parasitica R.W. Davidson and R.C. Lorenz is the causative agent of Eutypella canker of maple, a destructive disease of maples in Europe and North America. The fungus E. parasitica infects the trunk through a branch stub or bark wound. Because the fungal community may have an impact on infection and colonization by E. parasitica, the composition of fungi colonizing wood of dead branches of sycamore maple (Acer pseudoplatanus L.) was investigated in five sampling sites in Slovenia. Forty samples from each sampling site were collected between the November 2017 and March 2018 period. Isolations were made from the wood in the outer part of dead branches and from discoloured wood in the trunk that originated from a dead branch. Pure cultures were divided into morphotypes, and one representative culture per morphotype was selected for further molecular identification. From a total of 2700 cultured subsamples, 1744 fungal cultures were obtained, which were grouped into 212 morphotypes. The investigated samples were colonized by a broad spectrum of fungi. The most frequently isolated species were Eutypa maura (Fr.) Sacc., Eutypa sp. Tul. and C. Tul., Fusarium avenaceum (Fr.) Sacc., Neocucurbitaria acerina Wanas., Camporesi, E.B.G. Jones and K.D. Hyde and E. parasitica. In this study, we distinguished species diversity and the fungal community. There were no significant differences in the diversity of fungal species between the five sampling sites, and branch thickness did not prove to be a statistically significant factor in fungal species diversity. Nevertheless, relatively low Jaccard similarity index values suggested possible differences in the fungal communities from different sampling sites. This was confirmed by an analysis of similarities, which showed that the isolated fungal community distinctly differed between the five sampling sites and between the different isolation sources. Eutypella parasitica was isolated from all five investigated sampling sites, although Eutypella cankers were observed in only three sampling sites, indicating the possibility of asymptomatic infection.

Canker and Wood Rot Pathogens Present in Young Apple Trees and Propagation Material in the Western Cape of South Africa

Canker and wood rot pathogens cause dieback and, in severe cases, the death of young apple trees. Recently, a higher occurrence of cankers was observed on 1-year-old apple trees in the Western Cape Province of South Africa. This study aimed to assess the phytosanitary status of nursery trees and propagation material as possible inoculum sources for canker pathogens. Thirteen 1-year-old apple orchards showing canker or dieback symptoms were sampled. Certified nursery apple trees were collected from four nurseries as well as scion and rootstock mother plant material. Isolations were made from the discoloration observed in the vascular tissue of the plant parts and from asymptomatic material. Possible canker and wood rot species were identified with PCR and sequence comparisons of the relevant gene regions and phylogenetic analyses. Similar canker and wood rot species were isolated from 1-year-old diseased apple trees, nursery apple trees, and the propagation material. Forty-five fungal species associated with canker or wood rot symptoms were identified. The top five most abundant fungal species found causing disease on commercial 1-year-old trees were also found in high numbers causing latent infection in certified apple nursery trees. These species were Didymosphaeria rubi-ulmifolii sensu lato, Diplodia seriata, Schizophyllum commune, Didymella pomorum, and Coniochaeta fasciculata, with D. rubi-ulmifolii sensu lato being the dominant species in both sampling materials. In all, 65% of certified nursery apple trees, 5% of scion shoots used for budding, and 21% of rooted rootstock cuttings from layer blocks had latent infections of canker and wood rot pathogens. Pathogenicity trials were conducted with isolates of 39 species, inoculated onto 2-year-old branches of 14-year-old Golden Delicious trees. All species caused lesions that were significantly longer than the control. This study confirmed the presence of canker and wood rot pathogens in apple propagation material as well as certified nursery apple trees, which will aid the improvement of management practices in nurseries.

Quantitative Assessment of Grapevine Wood Colonization by the Dieback Fungus Eutypa lata

Eutypa lata is a fungal pathogen causing severe dieback in vineyards worldwide. This fungus colonizes vines through pruning wounds, eventually causing a brown sectorial necrosis in wood as well as stunted vegetative growth. Several years may pass between infection and the expression of external symptoms, hindering the rapid evaluation of both grapevine cultivars susceptibility and E. lata variation in aggressiveness. We aimed to develop a rapid quantitative method for the assessment of wood colonization after inoculation of cuttings in controlled conditions. We used several grape cultivars varying in susceptibility in the vineyard and fungal isolates with different levels of aggressiveness to monitor wood colonization during a maximum period of 2 months. Re-isolation allowed demonstration of the effects of both cultivars and fungal isolates on the rate of wood colonization. We also developed a real-time PCR method that was efficient in measuring fungal biomass, which was found to be correlated with isolate aggressiveness based on foliar symptom severity. The real-time PCR approach appears to be a useful technology to evaluate grapevine susceptibility to E. lata, and could be adapted to other pathogens associated with grapevine trunk diseases.

Trunk Disease Fungi Associated With Diospyros kaki in South Africa

Persimmon trees with dieback symptoms and cankers were observed in three production areas in Western Cape Province in South Africa. Isolations were made from diseased branches, cankers, and pruning wounds as well as fungal fruiting bodies on dead branches and old pruning wounds. Several trunk disease pathogens were identified based on morphological characteristics and by molecular methods, including Diaporthe eres, D. infecunda, Eutypella citricola, E. microtheca, Phaeoacremonium parasiticum, P. scolyti, P. australiense, P. minimum, Fomitiporia capensis, Fomitiporia sp., Fomitiporella sp., and Inocutis sp., which were isolated from persimmon for the first time in the world. Other first reports from persimmon in South Africa include D. foeniculina, D. ambigua, D. mutila, Diaporthe sp., Neofusicoccum australe, N. parvum, Diplodia seriata, and Eutypa lata. Pathogenicity tests conducted with all species, except the basidiomycetes, confirmed their status as possible persimmon pathogens. This is the first study to determine and identify fungi associated with diseased persimmon in South Africa. The knowledge gained in this study forms the basis for further research to determine the impact of these fungi on persimmon productivity.

Detection of Grapevine Fungal Trunk Pathogens on Pruning Shears and Evaluation of Their Potential for Spread of Infection

Four vineyards visibly affected by trunk diseases were surveyed at pruning time in 2012 and 2013 in Spain, to determine whether pruning tools are capable of spreading grapevine trunk diseases from vine to vine. In each vineyard, pruning shears were regularly rinsed with sterile water, collecting liquid samples for analysis. Molecular detection of grapevine fungal trunk pathogens (GFTPs) was performed by nested polymerase chain reaction using specific primers to detect Botryosphaeriaceae spp. Eutypa lata, Cadophora luteo-olivacea, Phaeoacremonium spp., and Phaeomoniella chlamydospora. All of these GFTPs, with the exception of E. lata, were detected in samples from the four vineyards, C. luteo-olivacea and Phaeoacremonium spp. being the most prevalent. Co-occurrence of two, three, or four different GFTPs from the same sample were found, the simultaneous detection of C. luteo-olivacea and Phaeoacremonium spp. being the most prevalent. In addition, fungal isolation from liquid samples in semiselective culture medium for C. luteo-olivacea, Phaeoacremonium spp., and P. chlamydospora was also performed but only C. luteo-olivacea was recovered from samples collected in three of four vineyards evaluated. Pruning shears artificially infested with suspensions of conidia or mycelial fragments of C. luteo-olivacea, Diplodia seriata, E. lata, Phaeoacremonium aleophilum, and Phaeomoniella chlamydospora were used to prune 1-year-old grapevine cuttings of '110 Richter' rootstock. Successful fungal reisolation from the cuttings 4 months after pruning confirmed that infested pruning shears were able to infect them through pruning wounds. These results improve knowledge about the epidemiology of GFTPs and demonstrate the potential of inoculum present on pruning shears to infect grapevines.

Molecular Polymorphism and Phenotypic Diversity in the Eutypa Dieback Pathogen Eutypa lata

Pathogen adaptation to different hosts can lead to specialization and, when coupled with reproductive isolation, genome-wide differentiation and ecological speciation. We tested the hypothesis of host specialization among California populations of Eutypa lata (causal fungus of Eutypa dieback of grapevine and apricot), which is reported from >90 species. Genetic analyses of nine microsatellite loci in 182 isolates from three hosts (grapevine, apricot, and willow) at three locations were complemented by cross-inoculations on cultivated hosts grapevine and apricot to reveal patterns of host specialization. The cultivated hosts are likely more important sources of inoculum than the wild host willow, based on our findings of higher pathogen prevalence and allelic richness in grapevine and apricot. High levels of gene flow among all three hosts and locations, and no grouping by clustering analyses, suggest neither host nor geographic differentiation. Cross-inoculations revealed diversified phenotypes harboring various performance levels in grapevine and apricot, with no apparent correlation with their host of origin. Such phenotypic diversity may enable this pathogen to persist and reproduce as a generalist. Regular genetic reshuffling through sexual recombination, frequent immigration among hosts, and the lack of habitat choice in this passively dispersed fungus may prevent fixation of alleles controlling host specialization.

Identification of Eutypa spp. Causing Eutypa Dieback of Grapevine in Eastern North America

Eutypa dieback of grapevine is caused by Eutypa lata in production areas with Mediterranean climates in California, Australasia, Europe, and South Africa. Eutypa dieback has also been described in the colder, eastern North American vineyards where cultivars adapted from native Vitis spp. (e.g., Vitis × labruscana 'Concord') are primarily grown. However, the causal agents associated with the diseases in this region have not been conclusively identified. Examination of 48 vineyards showing symptoms of dieback in the northeastern United States (Connecticut, Massachusetts, Michigan, New York, Ohio, and Rhode Island) and Ontario, Canada revealed that vineyards were mainly infected by Eutypa spp. other than E. lata. Multigene phylogenies (internal transcribed spacer ribosomal DNA, β-tubulin, and RNA polymerase II) of isolates recovered from these vineyards indicated that Eutypa dieback is caused primarily by an undescribed Eutypa sp. and E. laevata. Eutypa sp. was recovered from 56% of the vineyards examined, whereas E. laevata and E. lata were less far common (17 and 6%, respectively). Fruiting body morphology and spore dimensions supported phylogenetic separation of the three taxa. Pathogenicity tests conducted on Vitis vinifera 'Chardonnay' in the greenhouse and in the field verified that all three species were able to cause wood canker and to infect pruning wounds, respectively.

Pathogenicity of Diatrypaceous Fungi on Grapevines in Australia

In addition to Eutypa lata, which causes Eutypa dieback, numerous other fungi in the Diatrypaceae family have been isolated from diseased grapevines (Vitis vinifera) and other woody hosts. Pathogenicity trials comprising 70 strains of diatrypaceous fungi representing nine species in six genera were conducted to determine whether these fungi, collected in Australia, were pathogenic to grapevines. When inoculated into wounded trunks of 'Cabernet Sauvignon', eight species, including E. lata, E. leptoplaca, Cryptovalsa ampelina, C. rabenhorstii, Eutypella citricola, E. microtheca, Diatrypella vulgaris, and a Diatrype sp. produced necrotic lesions significantly longer than on controls. In addition, all nine species (including a Cryptosphaeria sp.) were reisolated from the margins of developing lesions and at varying distances above and below the point of inoculation. Diatrypaceous fungi were frequently isolated from asymptomatic or otherwise healthy tissue several centimeters ahead of the disease margin. Methods to control diseases associated with diatrypaceous fungi must take into account their propensity to colonize woody tissues ahead of or in the absence of visible symptoms. Current recommendations for the management of Eutypa dieback using remedial surgery and pruning wound protection appear sufficient for the control of the other diatrypaceous fungi included in this study.