Dothiorella Iberica Research Articles

Diversity and Pathogenicity of Botryosphaeriaceae Species Isolated from Olives in Istria, Croatia, and Evaluation of Varietal Resistance.

During 2021 and 2022, a field investigation was conducted in Istria, Croatia, searching for trees exhibiting signs of Botryosphaeria dieback. Samples of symptomatic trees were collected from 26 different locations and analysed. Isolates that morphologically corresponded to species from the Botryosphaeriaceae family were selected, and detailed morphological characterisation and molecular identification of the isolates were conducted. Based on morphological characteristics and phylogenetic analysis using the internal transcribed spacer (ITS), beta-tubulin (TUB2), and translation elongation factor 1-alpha (TEF1-α) regions, six species of fungi from the Botryosphaeriaceae family were identified: Botryosphaeria dothidea (Moug. ex Fr.) Ces. & De Not.; Diplodia mutila (Fr.) Fr.; Diplodia seriata De Not.; Dothiorella iberica A.J.L. Phillips, J. Luque & A. Alves; Dothiorella sarmentorum (Fr.) A.J.L. Phillips, Alves & Luque; and Neofusicoccum parvum (Pennycook & Samuels) Crous, Slippers & A.J.L. Phillips. This is the first report of D. mutila, Do. sarmentorum, and Do. iberica causing Botryosphaeria dieback on olive trees in Croatia, and the first study investigating the resistance of Croatian olive varieties to species from the Botryosphaeriaceae family. Pathogenicity testing of selected isolates and assessment of variety resistance were conducted on four different olive varieties, namely Buža, Istarska bjelica, Leccino, and Rosinjola, using representative isolates of the mentioned species. The most aggressive species was found to be N. parvum. Olive varieties exhibited differences in susceptibility depending on the fungus they were infected with.

Botryosphaeriaceae Species Associated with Stem Canker, Shoot Blight and Dieback of Fraxinus ornus in Italy

A severe dieback of flowering ash (Fraxinus ornus L.) has been observed in north-central Italy in the last decades. Symptoms include typical sunken, light-brown cankers on the stem and branches; vascular discoloration; tip and shoot dieback; and foliage necroses. The disease was more evident at the beginning of the growing season, and more severe on young regeneration. Six Botryosphaeriaceae species were consistently isolated from symptomatic plant tissues: Botryosphaeria dothidea, Diplodia fraxini, Diplodia subglobosa, Dothiorella iberica, Dothiorella omnivora and Neofusicoccum parvum. B. dothidea and D. fraxini expressed higher aggressiveness and showed a widespread incidence, being the species most frequently associated with cankers; the other four species were less virulent and more erratic, occurring mainly on succulent branch tips and foliage. Isolates were characterized using morphological and molecular approaches (colony/conidial phenotyping and rDNA-ITS genotyping). Phylogenetic analysis provided congruent phylogenies depicting the relationships of the six taxa with the most closely related conspecifics. Pathogenicity tests on 2-year-old seedlings confirmed the higher virulence of B. dothidea and D. fraxini. Extensive, multi-year field surveys at different sites supported the hypothesis that climatic vagaries, mainly heat, water and drought stresses, impaired tree health and vigor, facilitating infection and pervasive colonization by these Botryosphaeriaceae species. Environmental stressors are thus the key factor bringing the six fungal pathogens together in a multitrophic interaction with F. ornus in a novel, lethal fashion.

Fungal Pathogens Associated with Almond Decline Syndrome, an Emerging Disease Complex in Intensive Almond Crops in Southern Spain.

In 2016, an almond (Prunus dulcis) decline syndrome (ADS) emerged in intensive almond plantations in the Andalusia region (southern Spain), showing branch dieback, gummosis, and general tree decline. The aim of this work was to elucidate the etiology of this disease complex. For this purpose, surveys were conducted across the Andalusia region, and a wide collection of fungi was recovered from wood samples showing gum and internal discoloration. Representative isolates were selected and identified by sequencing ITS, TEF1, TUB, ACT, LSU, and/or RPB2 genes. The following fungal species were identified to be associated with the disease: Botryosphaeria dothidea, Diplodia corticola, Di. seriata, Dothiorella iberica, Lasiodiplodia viticola, Macrophomina phaseolina, Neofusicoccum mediterraneum, N. parvum, N. vitifusiforme, Diaporthe neotheicola, Dia. rhusicola, Dia. ambigua, Eutypa lata, E. tetragona, Eutypella citricola, Eu. microtheca, Fusarium oxysporum s.l., Pleurostoma richardsiae, Phaeoacremonium iranianum, Pm. krajdenii, Pm. parasiticum, and Cytospora sp. All isolates were tested for pathogenicity by inoculating detached or attached almond shoots. Di. corticola and N. parvum were the most aggressive species, showing the largest lesions and most gummosis in attached shoots. The results suggest that the species belonging to Botryosphaeriaceae play a key role in disease development, while the remaining identified species may act as secondary pathogens or endophytes. However, further research to determine the interaction between all these fungal species and other biotic and abiotic factors in the ADS progress is needed.

Isolation, molecular characterization and first report of Dothiorella gregaria associated with fruit rot of walnuts of Jammu and Kashmir, India.

Walnuts are known for their high levels of antioxidants, which are linked to various health benefits. However, challenges related to distribution and storage, as well as the risk of fungal infections, can affect the quality of walnut kernels. Fungal pathogens from the Botryosphaeriaceae family, including Dothiorella species and Diplodia species, can damage fruit and reduce its antioxidant content. To comprehend the cause of fruit rot in walnuts, Dothiorella gregaria isolates were studied using polyphasic methods, including multiple gene sequences and morphological identification, as well as analysis of polyphenol content and pathogenicity. The walnuts kernels purchased from market places of Jammu and Kashmir (J&K), India were observed to be affected by Dothiorella gregaria species causing the quality detoriation and decrease in polyphenol content thus undeniably with decreased antioxidant properties. D. gregaria Infected walnut kernels were having some brown and black spots and some were having white mycelial growth and however, most samples were asymptomatic. Pathogenicity testing revealed that the pathogen was able to develop all the symptoms under experimental conditions and the reisolated pathogen was morphologically similar to D. gregaria. The samples infected with this pathogen showed considerable decrease in polyphenol content, 10.9±2.66 mgGAE/g (mean±standard deviation) thus decreased antioxidant quality as compared to the samples which showed zero incidence of this pathogen, 52.50±4.27 mgGAE/g (mean±standard deviation). Furthermore, the pathogen was studied using polyphasic approach involving morphological, molecular and phylogenetic analysis. Combined nucleotide dataset of nuclear ribosomal ITS and tef1-α revealed that Dothiorella gregaria (NY6) formed a clade with Dothiorlla iberica (MAEC33), Dothiorella sarmentorium (MAEC28) and Dothiorella iberica (CAA905) strains with 83% bootstrap support. Besides, we observed six nucleotide changes, four were insertions or deletions and two were substitutions in the 502-bp region of the ITS rRNA gene when we compared our isolate to the most equivalent sequences submitted to NCBI GenBank. This is the first report of Dothiorella gregaria affecting walnuts purchased from various markets in J&K, India, causing fruit rot in walnuts after harvest. Given that local farmers store and export walnuts, it could pose an emerging threat to their livelihood. Thus, creating post-harvesting interventions for D. gregaria and knowing more about the fruit rot in walnuts can be benefited from morphological and molecular identification using several gene loci, genetic variability in the ITS rRNA gene, and total phenol analysis.

The first find of Naohidea sebacea (Naohideales, Basidiomycota) in Ukraine

The article provides information about a rare fungicolous fungus Naohidea sebacea first recorded in Ukraine in Roztochchia Nature Reserve. It was found to parasitize Dothiorella iberica (Botryosphaeriaceae, Botryosphaeriales, Dothideomycetes, Ascomycota). This host is reported for N. sebacea for the first time. Light microscopy, cultural studies, and nucleotide sequence analysis of the ITS-region of the ribosomal DNA were used to identify specimens. The resulting sequences were uploaded to the GenBank database. Based on the analysis of literature sources and personal data, information on morphological features, distribution, and substrate specialization of the fungus is provided.

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.

Diversity, distribution and host association of Botryosphaeriaceae species causing oak decline across different forest ecosystems in Algeria

Botryosphaeriaceous fungi associated with holm (Q. ilex) and cork (Q. suber) oak trees exhibiting dieback symptoms and cankers in Algeria, were sampled in twelve regions with different ecological conditions. Based on phylogenetic analyses of ITS and tef1-α loci, 13 species were identified. Three species (Diplodia corticola, Dothiorella iberica and Botryosphaeria dothidea) were found to be common to both oak species, while Doth. sarmentorum, D. mutila, Neofusicoccum vitifusiforme, D. insularis, N. stellenboschiana, Doth. plurivora, D. seriata, D. rosacearum, N. parvum and N. terminaliae were found only on one of the hosts. All the Botryosphaeriaceae taxa inoculated on oak shoots produced brown vascular discolouration, and were shown to be pathogenic on both oak species. Diplodia corticola was the most widespread and frequent species showing the highest aggressiveness towards both hosts. Neofusicoccum stellenboschiana, D. insularis and Doth. plurivora are recorded for the first time on Q. suber and Q. ilex. In addition to altitude, the environmental factors temperature and drought appeared to be influential variables that could describe the occurrence and the geographic distribution of these fungal species.

Botryosphaeriaceae species on forest trees in Portugal: diversity, distribution and pathogenicity

Fungi in the family Botryosphaeriaceae are known as pathogens of diverse woody hosts, including forest tree species. Although, several of these fungi have been described in different forest hosts in Portugal, their diversity and distribution is still poorly understood. A survey was conducted across the country to identify Botryosphaeriaceae species associated with the main forest tree species in Portugal, Quercus suber, Eucalyptus globulus and Pinus pinaster. Additionally, a meta-analysis was performed to compile and organize all records known from Portugal. From this meta-analysis, 22 different Botryosphaeriaceae species were reported and 40 different plant hosts were recorded in several studies from agricultural crops to ornamental and forest species. A total of 105 host-pathogen interactions were identified. In the national survey, 12 Botryosphaeriaceae species were identified, with Diplodia corticola being the most frequent. Diplodia insularis, Diplodia pyri, Dothiorella plurivora and Dothiorella yunnana are reported for the first time in Portugal. Of the 23 different host-fungus associations identified, 10 are also recognised as new hosts. Artificial inoculation tests confirmed the pathogenicity of all species, except Dothiorella iberica, Dothiorella plurivora and Dothiorella yunnana, which are regarded as weakly or non-pathogenic to the hosts tested. Pathogenicity tests revealed the host-jump potential of some species, showing high susceptibility of Q. suber to Neofusicoccum parvum and N. eucalyptorum and of P. pinaster to D. corticola. Our results show that Botryosphaeriaceae species have a widespread distribution across the country, however some species such as D. corticola, D. sapinea and N. eucalyptorum exhibit a distribution that overlaps the distribution of their preferred hosts.

Plant Pathogenic Fungi Associated with Coraebus florentinus (Coleoptera: Buprestidae) Attacks in Declining Oak Forests

The black-banded oak borer, Coraebus florentinus, is an emerging pest of oak trees in the western Mediterranean region. Larvae of the insect are xylophagous and progressively excavate an annular gallery that interrupts sap flow, resulting in the death of the attacked branches. Until now, limited information has been available regarding the ecological interactions between C. florentinus and the main plant pathogenic fungi involved in the etiology of oak decline. Knowledge of these interactions is important in understanding their impact in natural ecosystems and developing appropriate management strategies. Therefore, in this study, we characterized the fungal communities occurring in the exoskeleton of adults and larvae of C. florentinus and associated with the necrotic wood tissues surrounding the branch galleries of declining oak trees. A total of 29 fungal species were identified based on DNA sequence data and morphological features, of which 14 were from symptomatic woody tissues, six from insect exoskeleton, and nine from both insects and symptomatic wood tissues. The most frequent fungal species, Cryphonectria naterciae (15.9% of isolates), Dothiorella iberica (11.3%), and Diplodia corticola (9.9%), were isolated from both insect and gallery systems. All three species are well-known oak pathogens and are reported here, for the first time, to be associated with C. florentinus. At the same time, 89.6% of the fungal taxa were isolated from one or two sites, highlighting the site-dependence of fungal community assemblages.

Characterization and Pathogenicity of Botryosphaeriaceae Species Obtained from Avocado Trees with Branch Canker and Dieback and from Avocado Fruit with Stem End Rot in Chile.

Several species of the Botryosphaeriaceae family have been associated with branch canker, dieback, and stem end rot in avocado (Persea americana Mill.). In Chile, the incidence of diseases affecting the avocado tree increased from 2011 to 2016, which coincided with a severe drought that affected avocado production. Moreover, distant countries importing avocados from Chile also reported an increase of stem end rot of ripe avocados. Therefore, the aims of this study were to identify the pathogen species associated with branch canker, dieback, and stem end rot of avocado in Chile and to study their pathogenicity. This study was conducted between 2015 and 2016 in 'Hass' avocado orchards located in the main avocado-producing regions in Chile. A diverse collection of fungal species was recovered from both necrotic woody tissue and necrotic tissue on harvested ripe fruit. On the basis of morphology and phylogenetic analyses of the internal transcribed spacer region (ITS1-5.8S-ITS2) and the translation elongation factor 1-α (TEF1-α) gene, eight species in the Botryosphaeriaceae family were identified: Diplodia mutila, D. pseudoseriata, D. seriata, Dothiorella iberica, Lasiodiplodia theobromae, Neofusicoccum australe, N. nonquaesitum, and N. parvum. For each of these species, pathogenicity studies were conducted on 1-year-old healthy Hass avocado plants. All isolates produced brown gum exudate and caused necrosis in the vascular system 3 weeks after inoculation. N. nonquaesitum, N. parvum, and D. pseudoseriata were the most virulent species. Necrotic lesions and cavities with white mycelia near the peduncle union were observed on Hass avocado fruit inoculated postharvest. L. theobromae, N. australe, and N. parvum were significantly more virulent than the other tested species in the Botryosphaeriaceae family. This study identified and characterized the pathogenicity of Botryosphaeriaceae species in Chile, which will prove useful to future research on these pathogens directed at establishing effective control strategies in avocado.

Grapevine trunk disease in German viticulture II. Associated fungi occurring on non-Vitis hosts, and first report of Phaeoacremonium angustius

Fifteen species of wood colonizing fungi are presented that have been collected from various non-Vitis hosts in the vicinity of vineyards located in southern Palatinate, Germany. Information is provided on their geographic distribution, epidemiology, host range, life strategy, symptoms and diagnosis. Their role as possible pathogens within the complex of grapevine trunk diseases (GTDs) is discussed. The following species are reported for the first time in Germany: Botryosphaeria sarmentorum, Cadophora malorum, Cadophora novi-eboraci, Collophora africana, Collophora hispanica, Cytospora chrysosperma, Diaporthe foeniculina, Dothiorella iberica, and Phaeoacremonium angustius. Diplodia seriata, Diplodia mutila, Dothiorella iberica, Cytospora chrysosperma, and Dothiorella iberica were proven by airborne inoculum, and could be demonstrated throughout the duration of our study, i.e. from March through September. The study points to a possible significance of non-Vitis hosts as additional inoculum source in GTDs. Also, the existence of airborne spores early in the year might be relevant with regard to the pruning period of vines.

Phylogeny, morphology and pathogenicity of Botryosphaeriaceae, Diatrypaceae and Gnomoniaceae associated with branch diseases of hazelnut in Sardinia (Italy)

Severe trunk and branch diseases of hazelnut trees have recently been observed in several groves in Sardinia (Italy). Since there is little information about the aetiology of these diseases and given the high ecological and economic importance of these agro-systems, an in-depth study was carried out. From autumn 2012 to spring 2014, sixty samples of twigs and branches of hazelnut trees showing exudates and different types of canker (sunken with wedge-shaped necrotic sector, open canker and Cytospora canker) were collected in the main hazelnut growing area in the centre of the island. Based on morphology, colony appearance and DNA sequence data, seven species belonging to four genera and three families were isolated and identified. These included Diplodia sapinea, D. seriata, Dothiorella iberica, Do. parva and Do. symphoricarposicola (Botryosphaeriaceae), Gnomoniopsis smithogilvyi (Gnomoniaceae) and Anthostoma decipiens (Diatrypaceae). In addition, two new species namely Diaporthella cryptica sp. nov. and Dothiorella omnivora sp. nov. are described. Pathogenicity trials carried out on wounded hazelnut branches showed that three species, Anthostoma decipiens, Diaporthella cryptica and Diplodia seriata are aggressive pathogens on hazelnut. Results obtained have allowed us to clarify, almost a century after its first description, the aetiology of the disease known as Cytospora canker of hazelnut and to reveal the existence of three evolutionarily distinct lineages for its causal agent A. decipiens. The diversity of fungal pathogens associated with twig and branch cankers of hazelnut is greater than previously recognised and further studies are necessary to determine the exact role played by each species and their possible synergistic interaction.

Characterization of Botryosphaeriaceae Species as Causal Agents of Trunk Diseases on Grapevines.

Botryosphaeriaceae spp. have a cosmopolitan distribution and a wide range of plant hosts. Over the last 15 years, worldwide, 21 species of this family have been associated with grapevine trunk diseases that cause cankers and dieback on grapevines. Here, we surveyed vineyards of Vitis vinifera 'Lambrusco', 'Sangiovese', and 'Montepulciano' in three areas of the Foggia province (Cerignola, Foggia, and San Severo) in southern Italy. Wood samples from grapevines showing general decline, dieback, cankers, and wood and foliar discoloration yielded 344 fungal isolates identified as Botryosphaeriaceae spp. A phylogenetic study combining internal transcribed spacer and translation elongation factor 1-α sequences of 60 representative isolates identified nine botryosphaeriaceous species: Botryosphaeria dothidea, Diplodia corticola, D. mutila, D. seriata, Dothiorella iberica, Do. sarmentorum, Lasiodiplodia citricola, L. theobromae, and Neofusicoccum parvum. Pathogenicity tests confirmed that all nine species cause canker and dieback of grapevines. However, this is the first report of L. citricola as causal agent of wood cankers and dieback of grapevine. To date, including L. citricola, there are 25 botryosphaeriaceous species associated with V. vinifera worldwide, of which 12 have been reported for grapevines in Italy.

First Report of Dothiorella iberica Causing Trunk and Scaffold Cankers of Almond in California

First Report of <i>Dothiorella iberica</i> Causing Trunk and Scaffold Cankers of Almond in California

Phylogeny, Morphology, Distribution, and Pathogenicity of Botryosphaeriaceae and Diaporthaceae from English Walnut in California.

Species of family Botryosphaeriaceae and genus Diaporthe (anamorph: genus Phomopsis, family Diaporthaceae) were reported and caused diseases on various fruit and nut trees in California. In the last several years, diseases on English walnut (Juglans regia) caused by species of Botryosphaeriaceae and Diaporthe were observed frequently in California. Disease symptoms include stem canker; shoot canker and blight; twig, leaf, and fruit blight; and necrotic leaf lesions. Isolates of the pathogen were collected from English walnut in 13 counties in California. The aims of this study were to identify these isolates and to test their pathogenicity to English walnut cultivars. In total, 159 California isolates were identified based on comparisons of DNA sequence data of the internal transcribed spacer, translation elongation factor 1-α, and β-tubulin gene regions, and combined with the morphological features of the cultures and conidia. Research results revealed that isolates represent 10 species of Botryosphaeriaceae and two species of Diaporthe. These species include Botryosphaeria dothidea, Diplodia mutila, D. seriata, Dothiorella iberica, Lasiodiplodia citricola, Neofusicoccum mediterraneum, N. nonquaesitum, N. parvum, N. vitifusiforme, Neoscytalidium dimidiatum, Diaporthe neotheicola, and D. rhusicola. Pathogenicity on three English walnut cultivars ('Chandler', 'Tulare', and 'Vina') using a mycelium plug inoculation method revealed that all these species are pathogenic to all the tested cultivars, with L. citricola and N. parvum being the most pathogenic species, followed by N. mediterraneum, N. dimidiatum, and B. dothidea. Chandler was more tolerant to infection than Tulare and Vina. Results in this study determined that multiple numbers of the Botryosphaeriaceae fungi and two Diaporthe spp. cause cankers and blights of English walnut and vary in their virulence from highly to slightly virulent, respectively.

Botryosphaeriaceae and Diaporthaceae associated with panicle and shoot blight of pistachio in California, USA

Botryosphaeria panicle and shoot blight was considered as one of the single greatest threats to the California pistachio industry in the last two decades. A large number of fungi with typical morphological characteristics of Botryosphaeriaceae and Diaporthe were collected from pistachios in 18 counties in California and deposited in our culture collection. The aims of this study were to identify these isolates, recognize the distribution of these fungal species and test their pathogenicity to pistachio cultivars. A total of 304 California isolates were identified based on comparisons of DNA sequence data of the ITS, TEF-1α and β-tubulin gene regions, and combined with the morphological features of the cultures and conidia. Research results showed that California isolates represent eight species of Botryosphaeriaceae and one species of Diaporthe. These species include Botryosphaeria dothidea, Diplodia seriata, Dothiorella iberica, Dot. sarmentorum, Lasiodiplodia citricola, L. gilanensis, Neofusicoccum mediterraneum, Neof. vitifusiforme and Diaporthe chamaeropis. Of the Botryosphaeriaceae, 86 % of the isolates were identified as Neof. mediterraneum, which distributed in all the sampled counties. On pistachio trees, in addition to isolates from California, Neof. mediterraneum from Arizona, Neof. australe from Australia, B. dothidea, Neof. parvum and Dia. viticola from Greece were also identified. Pathogenicity of the California fungi on pistachio cultivars, Kerman (female) and Peters (male), using a mycelium plug and conidial suspension inoculation methods showed that all these species are pathogenic to the two tested pistachio cultivars, with L. citricola, L. gilanensis being the most pathogenic species, followed by Neof. mediterraneum. This study represents the first comprehensive work on the species identification, distribution and pathogenicity of Botryosphaeriaceae and Diaporthe on pistachio in California.

Occurrence, incidence and associations among fungal pathogens and Agrilus auroguttatus, and their roles in Quercus agrifolia decline in California

SummarySynchronous decline of oak (Quercus spp.) trees in woodlands has been described in Europe and eastern North America as a complex interaction of stressors that predispose, incite or contribute to tree death. This study presents a 2‐year (2010–2011) assessment of the role of pathogens in coast live oak (Quercus agrifolia) woodlands in southern California where oak mortality occurs in locations that are infested and uninfested by the goldspotted oak borer (GSOB, Agrilus auroguttatus). Cumulative coast live oak mortality was not significantly different between sites and was weakly correlated with Diplodia corticola and GSOB incidence and negatively correlated with annual relative humidity. Multiple logistic regression models explained the presence of individual fungi or GSOB at the tree level. Fisher's exact test analysis determined that the presence of D. corticola, Fusarium solani, Dothiorella iberica, Cryptosporiopsis querciphila and Diatrypella verrucaeformis were each related to origin of sample location on tree, and C. querciphila was additionally related to symptom type on the bole. Multiple linear regression models showed high correlation between environmental variables and plot‐level incidence of both GSOB and D. corticola. Disease incidence (DI) for D. corticola was highest in GSOB‐uninfested locations. Jaccard index of association (J) showed that D. corticola was negatively associated with the presence of GSOB, F. solani and C. querciphila. Results suggest that oak decline in California is an example of a complex syndrome involving strong regional differences in factors that are associated with the problem.

Effect of Fungicide Application on the Management of Avocado Branch Canker (Formerly Dothiorella Canker) in California.

Members of the Botryosphaeriaceae family have been associated with branch cankers of avocado trees (Persea americana) in California. Canker infections are initiated by spores entering the host plant through fresh wounds such as pruning wounds. With high-density planting becoming more common in the California avocado industry, more intensive pruning may increase the occurrence of branch canker. The objective of this study was to evaluate the preventive ability of some commercial fungicides belonging to different chemical families against fungal pathogens associated with avocado branch canker. Initially, 12 fungicides were tested in vitro for their effect on the inhibition of mycelial growth of three isolates of Dothiorella iberica and isolates (five per species) of Neofusicoccum australe, N. luteum, N. parvum, and Phomopsis sp. Subsequently, azoxystrobin, fludioxonil, metconazole, and pyraclostrobin, selected because of their low effective concentrations that reduce 50% of mycelial growth (EC50 values), and myclobutanil, selected for its high EC50 value, were tested in two field experiments. Azoxystrobin and fludioxonil were used in a premix with propiconazole and cyprodinil, respectively, in field trials. Significant differences (P < 0.05) were observed among fungicides in field trials. Azoxystrobin + propiconazole had the highest percent inhibition at 52 and 62% (internal lesion length) in trial 1 and trial 2, respectively, although this level of inhibition was not significantly different from that of metconazole. A significant correlation (r = 0.51, P < 0.05) was observed between internal lesion length data in the field experiment and EC50 data from in vitro fungicide screening. Application of azoxystrobin + propiconazole and metconazole can play a key role in protecting Californian avocado against fungi causing avocado branch canker.

Pathogenicity and epidemiology of Botryosphaeriaceae species isolated from grapevines in Australia

Botryosphaeriaceae species are among the most common fungi isolated from grapevine (Vitis vinifera) cankers in Australia. Thirty-eight isolates comprising eight Botryosphaeriaceae species isolated from grapevine cankers throughout New South Wales and South Australia were used in a pathogenicity study on mature wood of 15-year-old Chardonnay grapevines. Experiments showed that all eight species were able to infect grapevines under field conditions causing vascular discoloration and/or staining of the wood (lesions). However, differences in pathogenicity were evident among strains and species (P < 0.001). Neofusicoccum parvum and Lasiodiplodia theobromae were the most pathogenic based on lesion length, followed by Neofusicoccum australe, Botryosphaeria dothidea and Diplodia mutila and thereafter by Dothiorella viticola, Dothiorella iberica and Diplodia seriata, which were the least pathogenic. Growth rates also differed significantly among species depending on temperature (P < 0.001). Lasiodiplodia theobromae and B. dothidea grew optimally between 29 and 30 °C, Diplodia and Neofusicoccum spp. between 25 and 27 °C, and Dothiorella spp. at temperatures between 22 and 24 °C. Temperature-growth relationships correlated well with previous data on the prevalence and distribution of Botryosphaeriaceae species in Australian vineyards. Due to their pathogenicity, prevalence, distribution and tolerance to a wide range of environmental conditions, the Botryosphaeriaceae pose a significant threat to the Australian wine industry.

Olive Twig and Branch Dieback: Etiology, Incidence, and Distribution in California.

Eighteen different fungal species were isolated from symptomatic wood of olive trees (Olea europaea) affected by twig and branch dieback in California and identified by means of morphological characters and multigene sequence analyses of the internal transcribed spacer (ITS) region (ITS1-5.8S-ITS2), a partial sequence of the β-tubulin gene, and part of the translation elongation factor 1-α gene (EF1-α). These species included Diaporthe viticola, Diatrype oregonensis, Diatrype stigma, Diplodia mutila, Dothiorella iberica, Lasiodiplodia theobromae, Phaeomoniella chlamydospora, Phomopsis sp. group 1, Phomopsis sp. group 2, and Schizophyllum commune, which are for the first time reported to occur in olive trees; Eutypa lata, Neofusicoccum luteum, Neofusicoccum vitifusiforme, and Phaeoacremonium aleophilum, which are for the first time reported to occur in olive trees in the United States; and Botryosphaeria dothidea, Diplodia seriata, Neofusicoccum mediterraneum, and Trametes versicolor, which have been previously reported in olive trees in California. Pathogenicity studies conducted in olive cultivars Manzanillo and Sevillano showed N. mediterraneum and Diplodia mutila to be the most virulent species and Diatrype stigma and D. oregonensis the least virulent when inoculated in olive branches. Intermediate virulence was shown for the rest of the taxa. This study demystifies the cause of olive twig and branch dieback and elucidates most of the fungal pathogens responsible for this disease in California.