The incredible story of ophiobolin A and sphaeropsidin A: two fungal terpenes from wilt-inducing phytotoxins to promising anticancer compounds

Covering: 2000 to 2023This review presents the exceptional story of ophiobolin A (OphA) and sphaeropsidin A (SphA), a sesterterpene and a diterpene, respectively, which were initially isolated as fungal phytotoxins and subsequently shown to possess other interesting biological activities, including promising anticancer activities. Ophiobolin A is a phytotoxin produced by different fungal pathogens, all belonging to the Bipolaris genus. Initially, it was only known as a very dangerous phytotoxin produced by fungi attacking essential cereals, such as rice and barley. However, extensive and interesting studies were carried out to define its original carbon skeleton, which is characterized by a typical 5 : 8 : 5 ring system and shared with fusicoccins and cotylenins, and its phytotoxic activity on host and non-host plants. The biosynthesis of OphA was also defined by describing the different steps starting from mevalonate and through the rearrangement of the acyclic C-25 precursor lead the toxin is obtained. OphA was also produced as a bioherbicide from Drechslera gigantea and proposed for the biocontrol of the widespread and dangerous weed Digitaria sanguinaria. To date, more than sixty ophiobolins have been isolated from different fungi and their biological activities and structure-activity relationship investigated, which were also described using their hemisynthetic derivatives. In the last two decades, thorough studies have been performed on the potential anticancer activity of OphA and its original mode of action, attracting great interest from scientists. Sphaeropsidin A has a similar story. It was isolated as the main phytotoxin from Diplodia cupressi, the causal agent of Italian cypress canker disease, resulting in the loss of millions of plants in a few years in the Mediterranean basin. The damage to the forest, environment and ornamental heritage are noteworthy and economic losses are also suffered by tree nurseries and the wood industry. Six natural analogues of SphA were isolated and several interesting hemisynthetic derivatives were prepared to study its structure-activity relationship. Surprisingly, sphaeropsidin A showed other interesting biological activities, including antibiotic, antifungal, and antiviral. In the last decade, extensive studies have focused on the anticancer activity and original mode of action of SphA. Furthermore, specific hemisynthetic studies enable the preparation of derivatives of SphA, preserving its chromophore, which showed a noteworthy increase in anticancer activity. It has been demonstrated that ophiobolin A and sphaeropsidin A are promising natural products showing potent activity against some malignant cancers, such as brain glioblastoma and different melanomas.

Additions to Diatrypaceae (Xylariales): Novel Taxa and New Host Associations

Diatrypaceae members have a broad distribution and are commonly found on decaying wood. Despite taxonomic and morphological challenges within this group, there has been a growing interest in Diatrypaceae in recent years. The dead branches of several plant hosts with fungal fruiting bodies were collected from Doi Tung National Park, Chiang Rai, and the Narathiwat Provinces in Thailand. Their morphological characteristics, coupled with a molecular phylogeny of combined ITS and tub2 sequence data, were used to introduce two novel Allodiatrype species (A. dalbergiae and A. eleiodoxae) and one new Melanostictus species (M. chiangraiensis). Moreover, four new host records, Diatrypella heveae, D. major, Melanostictus thailandicus, and Paraeutypella citricola on Microcos paniculata, Nayariophyton zizyphifolium, Dalbergia cultrata, and M. paniculata, respectively, as well as a new geographical record of D. major are reported. This research provides detailed descriptions of macro- and microcharacteristics, coupled with a phylogenetic tree for the newly introduced species and host records. The morphological features of Allodiatrype and Melanostictus are listed in the synoptic table.

Comparative Analysis of Secondary Metabolites in Diplodia corticola Strains with Different Virulence Degrees Associated with Canker and Dieback of Quercus spp

Diplodia corticola is one of the most aggressive fungal pathogens of Quercus species involved in the decline of Mediterranean oak forests. In this study, three strains of D. corticola associated with holm (Quercus ilex) and cork (Quercus suber) oak trees exhibiting dieback symptoms and cankers in Algeria were selected to investigate the production of secondary metabolites. Metabolomic analyses revealed the production of several known compounds, such as sphaeropsidins, diplopyrones and diplofuranones. Moreover, the comparative investigation of secondary metabolites produced by the analyzed strains with different degrees of virulence revealed possible implications of these compounds in the fungal virulence. In particular, sphaeropsidins seem to be the main phytotoxic compounds of D. corticola involved in the infections of Quercus species, with a possible synergistic influence of the less representative compounds in the fungal virulence.

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.

Molecular and Biological Characterization of Two New Species Causing Peach Shoot Blight in China

Peach shoot blight (PSB), which kills shoots, newly sprouted leaf buds, and peach fruits, has gradually increased over the last 10 years and resulted in 30 to 50% of total production loss of the peach industry in China. Phomopsis amygdali has been identified as the common causal agent of this disease. In this study, two new species, Phomopsis liquidambaris (strain JW18-2) and Diaporthe eres (strain JH18-2), were also pathogens causing PSB, as determined through molecular phylogenetic analysis based on the sequences of the internal transcribed spacer (ITS) region, translation elongation factor 1-α (EF1-α) and beta-tubulin (TUB), and colony and conidial morphological characteristics. Biological phenotypic analysis showed that the colony growth rate of strain JW18-2 was faster than that of strains JH18-2 and ZN32 (one of the P. amygdali strains that we previously found and identified). All three strains produced α-conidia; however, JW18-2 could not produce β-conidia on alfalfa decoction and Czapek media, and the β-conidia produced by strain JH18-2 were shorter in length and thicker in width than those produced by strain ZN32. Pathogenicity tests showed that JW18-2 presented the strongest pathogenicity for peach fruits and twigs and was followed by strains JH18-2 and ZN32. The results shed light on the etiology of PSB and provide a warning that P. liquidambaris or D. eres might develop into dominant species after a few years while also potentially benefitting the development of effective disease control management strategies.

Fungi of quarantine concern for China I: Dothideomycetes

The current list of Chinese quarantine pests includes 130 fungal species. However, recent changes in the taxonomy of fungi following the one fungus = one name initiative and the implementation of DNA phylogeny in taxonomic revisions, resulted in many changes of these species names, necessitating an update of the current list. In addition, many quarantine fungi lack modern morphological descriptions and authentic DNA sequences, posing significant challenges for the development of diagnostic protocols. The aim of the present study was to review the taxonomy and names of the 33 Chinese quarantine fungi in Dothideomycetes, and provide reliable DNA barcodes to facilitate rapid identification. Of these, 23 names were updated according to the single name nomenclature system, including one new combination, namely Cophinforma tumefaciens comb. nov. (syn. Sphaeropsis tumefaciens). On the basis of phylogenetic analyses and morphological comparisons, a new genus Xenosphaeropsis is introduced to accommodate the monotypic species Xenosphaeropsis pyriputrescens comb. nov. (syn. Sphaeropsis pyriputrescens), the causal agent of a post-harvest disease of pears. Furthermore, four lectotypes (Ascochyta petroselini, Mycosphaerella ligulicola, Physalospora laricina, Sphaeria lingam), three epitypes (Ascochyta petroselini, Phoma lycopersici, Sphaeria lingam), and two neotypes (Ascochyta pinodella, Deuterophoma tracheiphila) are designated to stabilise the use of these names. A further four reference strains are introduced for Cophinforma tumefaciens, Helminthosporium solani, Mycocentrospora acerina, and Septoria linicola. In addition, to assist future studies on these important pathogens, we sequenced and assembled whole genomes for 17 species, including Alternaria triticina, Boeremia foveata, B. lycopersici, Cladosporium cucumerinum, Didymella glomerata, Didymella pinodella, Diplodia mutila, Helminthosporium solani, Mycocentrospora acerina, Neofusicoccum laricinum, Parastagonospora pseudonodorum, Plenodomus libanotidis, Plenodomus lingam, Plenodomus tracheiphilus, Septoria petroselini, Stagonosporopsis chrysanthemi, and Xenosphaeropsis pyriputrescens. Citation: Zhao P, Crous PW, Hou LW, et al. 2021. Fungi of quarantine concern for China I: Dothideomycetes. Persoonia 47: 45-105. https://doi.org/10.3767/persoonia.2021.47.02.

New contributions to Diatrypaceae from karst areas in China

In this study, fungal specimens of the family Diatrypaceae were collected from karst areas in Guizhou, Hainan and Yunnan Provinces, China. Morpho-molecular analyses confirmed that these new collections comprise a new genus Pseudodiatrype, three new species (Diatrypelancangensis, Diatrypellapseudooregonensis and Eutypacerasi), a new combination (Diatrypellaoregonensis), two new records (Allodiatrypethailandica and Diatrypellavulgaris) from China and two other known species (Neoeutypellabaoshanensis and Paraeutypellacitricola). The new taxa are introduced, based on multi-gene phylogenetic analyses (ITS, β-tubulin), as well as morphological analyses. The new genus Pseudodiatrype is characterised by its wart-like stromata with 5-20 ascomata immersed in one stroma and the endostroma composed of thin black outer and inner layers of large white cells with thin, powdery, yellowish cells. These characteristics separate this genus from two similar genera Allodiatrype and Diatrype. Based on morphological as well as phylogenetic analyses, Diatrypelancangensis is introduced as a new species of Diatrype. The stromata of Diatrypelancangensis are similar to those of D.subundulata and D.undulate, but the ascospores are larger. Based on phylogenetic analyses, Diatrypeoregonensis is transferred to the genus Diatrypella as Diatrypellaoregonensis while Diatrypellapseudooregonensis is introduced as a new species of Diatrypella with 8 spores in an ascus. In addition, multi-gene phylogenetic analyses show that Eutypacerasi is closely related to E.lata, but the ascomata and asci of Eutypacerasi are smaller. The polyphyletic nature of some genera of Diatrypaceae has led to confusion in the classification of the family, thus we discuss whether the number of ascospores per asci can still be used as a basis for classification.

Sphaeropsidin A: a Pimarane Diterpene with Interesting Biological Activities and Promising Practical Applications

Sphaeropsidin A (SphA) is a tetracyclic pimarane diterpene, first isolated as the main phytotoxin produced by Diplodia cupressi the causal agent of a severe canker disease of Italian cypress (Cupressus sempervirens L.). It was also produced, together with several analogues, by different pathogenic Diplodia species and other fungi and showed a broad array of biological activities suggesting its promising application in agriculture and medicine. The anticancer activity of SphA is very potent and cell specific. Recent studies have revealed its unique mode of action. This minireview reports the structures of SphA and its family of natural analogues, their biosynthetic origins, their fungal sources, and biological activities. The preparation of various SphA derivatives is also described as well as the results of structure-activity relationship (SAR) studies and on their potential practical applications.

Multigene Phylogeny Reveals Haploanthostomella elaeidis gen. et sp. nov. and Familial Replacement of Endocalyx (Xylariales, Sordariomycetes, Ascomycota)

During our investigation of palm fungi in Thailand, two interesting taxa from Elaeis guineensis and Metroxylon sagu (Arecaceae) were collected. Based on phylogenetic analyses of a combined dataset of ITS, LSU, rpb2, and tub2 nucleotide sequences as well as unique morphological characteristics, we introduce the new genus Haploanthostomella within Xylariales, and a new species Endocalyx metroxyli. Additionally, in our study, the genus Endocalyx is transferred to the family Cainiaceae based on its brown conidia and molecular phylogenetic evidence.

Paraeutypella guizhouensis gen. et sp. nov. and Diatrypella longiasca sp. nov. (Diatrypaceae) from China

Background

In this study, we introduce a novel genus, Paraeutypella, of the family Diatrypaceae comprising three species viz. Paraeutypellaguizhouensis sp. nov. and P.citricola (basionym: Eutypellacitricola) and P.vitis (basionym: Sphaeriavitis). Diatrypellalongiasca sp. nov. is also introduced, which forms a distinct clade in Diatrypella sensu stricto. The discovery of this new genus will contribute to expanding the knowledge and taxonomic framework of Diatrypaceae (Xylariales).

New information

Generic delimitations in Diatrypaceae are unsettled because the phylogeny has yet to be resolved using extensive taxon sampling and sequencing of ex-type cultures. During an investigation of xylarialean fungi, we collected eutypella-like fungi which is distinct from Eutypella sensu stricto in our phylogenetic analyses (ITS and β-tubulin), thus, introduced as Paraeutypellaguizhouensis gen. et sp. nov.. Paraeutypella is characterised by having 4–25 perithecia in a stroma each with 3–6 sulcate, long ostiolar necks. Paraeutypellacitricola comb. nov. (basionym: Eutypellacitricola) is introduced on Acer sp. from China. Diatrypellalongiasca sp. nov. is introduced as a new species in Diatrypella sensu stricto. which has 2–5 ascomata per stroma and long ascospores, unusual when compared to other Diatrypella species and distinct phylogenetically.

Stem Canker on Cyclocarya paliurus Is Caused by Botryosphaeria dothidea

Cyclocarya paliurus, an important endangered plant in China, has considerable medicinal, timber, and horticultural value. However, little is known about diseases that affect its health. In recent years, stem canker diseases on C. paliurus have been observed frequently in newly established nurseries in Jiangsu Province, China. Symptomatic trees showed elliptical, sunken lesions on the bark, with internal discoloration, leading to enlarging cankers with delineated margins. Pathogenicity tests with fungi isolated from symptomatic samples reproduced typical canker symptoms on both detached branches and potted plants of C. paliurus. Moreover, conidia from pycnidia of isolate ZB-23 could also cause stem canker on C. paliurus. Through combined morphological observation and DNA sequences of ITS region, β-tubulin, and translation elongation factor 1-α genes, the pathogen was identified as Botryosphaeria dothidea. Multigene maximum likelihood and maximum parsimony phylogenetic analyses further supported the identification of the pathogen. To our knowledge, this is the first report of B. dothidea causing stem canker on C. paliurus in China.

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 Fungi Associated with Declining Urban Stands of Coast Redwood in California

Coast redwood (Sequoia sempervirens) is among the most widely planted landscape trees in California (CA) but is in decline outside its natural range due to factors including prolonged drought and plant pathogens. We investigated associations of Botryosphaeriaceae fungi with declining coast redwood trees throughout CA. More than 100 samples were collected from 11 coastal and inland locations in CA. Fifty-nine Botryosphaeria-like fungal strains were isolated and 18 were selected for further study. Phylogenetic analysis of ITS and EF-1α sequence data confirmed the presence of Botryosphaeria dothidea, Neofusicoccum australe, N. luteum, N. mediterraneum, and N. parvum. Pathogenicity testing showed that although the Neofusicoccum species vary in virulence, all are more virulent that B. dothidea. N. australe caused the largest lesions, followed by N. luteum, N. parvum, and N. mediterraneum. Of the species recovered, only B. dothidea has been previously confirmed as a pathogen of coast redwood in CA. These results confirm that multiple Botryosphaeriaceae species are associated with branch decline and dieback on coast redwood in CA, which agrees with similar studies on woody agricultural crops. Accurate diagnosis of fungal pathogens of coast redwood is important for the development of disease management strategies and may help improve horticultural practices in maintenance of urban stands.

Neoscytalidium dimidiatum Causing Canker, Shoot Blight and Fruit Rot of Almond in California

Almond trees with trunk and branch cankers were observed in several orchards across almond-producing counties in California. Symptoms of cankers included bark lesions, discoloration of xylem tissues, longitudinal wood necrosis, and extensive gumming. Spur and shoot blight associated with rotted fruit were detected in two orchards in Kern County. The fungus Neoscytalidium dimidiatum was consistently recovered from the various cankers, infected fruit, and blighted shoots and its identity was confirmed based on phylogenetic and morphological studies. Phylogenetic analyses of the internal transcribed spacer, translation elongation factor 1-α, and β-tubulin genes comparing 47 strains from California with reference specimens within the family Botryosphaeriaceae and coupled with detailed morphological observations validated the identity of the pathogenic fungus. Pathogenicity tests conducted in the field using 1- to 2-year-old branches inoculated with mycelium plugs or conidial suspensions and attached fruit inoculated with conidial suspensions fulfilled Koch's postulates. N. dimidiatum appeared highly virulent in almond-producing cankers of up to 22 cm in length within 4 weeks using mycelium plug inoculations as well as severe fruit rot combined with spur blight on the fruit-bearing spurs. This study reports, for the first time, the fungus N. dimidiatum as a pathogen of almond in California causing canker, shoot blight, and fruit rot. Disease symptoms are described and illustrated.

Mating type gene analyses in the genus Diplodia: From cryptic sex to cryptic species

Cryptic species are common in Diplodia, a genus that includes some well-known and economically important plant pathogens. Thus, species delimitation has been based on the phylogenetic species recognition approach using multigene genealogies. We assessed the potential of mating type (MAT) genes sequences as phylogenetic markers for species delimitation in the genus Diplodia. A PCR-based mating type diagnostic assay was developed that allowed amplification and sequencing of the MAT1-1-1 and MAT1-2-1 genes, and determination of the mating strategies used by different species. All species tested were shown to be heterothallic. Phylogenetic analyses were performed on both MAT genes and also, for comparative purposes, on concatenated sequences of the ribosomal internal transcribed spacer (ITS), translation elongation factor 1-alpha (tef1-α) and beta-tubulin (tub2). Individual phylogenies based on MAT genes clearly differentiated all species analysed and agree with the results obtained with the commonly used multilocus phylogenetic analysis approach. However, MAT genes genealogies were superior to multigene genealogies in resolving closely related cryptic species. The phylogenetic informativeness of each locus was evaluated revealing that MAT genes were the most informative loci followed by tef1-α. Hence, MAT genes can be successfully used to establish species boundaries in the genus Diplodia.

Botryosphaeriaceae Species Associated With Cankers and Dieback Symptoms of Acacia mangium and Pinus caribaea var. hondurensis in Venezuela

Several species in the Botryosphaeriaceae family cause wood stain, cankers, and dieback of trunks and branches in a wide range of forest tree species. The aim of this study was to characterize the botryosphaeriaceous fungi associated with decline symptoms observed in Acacia mangium and Pinus caribaea var. hondurensis, two economically important forest tree species grown in commercial plantations in Venezuela. Fungi isolated from symptomatic samples collected from both hosts in commercial sites were identified based on their morphology and DNA sequences of the internal transcribed spacer region (ITS1-5.8S-ITS2) and part of the β-tubulin and translation elongation factor 1-α genes. Lasiodiplodia theobromae and L. venezuelensis were routinely isolated from A. mangium and P. caribaea var. hondurensis. Additionally, the novel species Diplodia guayanensis was isolated and characterized from symptomatic and asymptomatic tissues of A. mangium. Multigene phylogenetic analyses along with restriction fragment length polymorphism studies further supported the identification of these species. A pathogenicity study was conducted under natural conditions and 12 weeks after inoculation all Botryosphaeriaceae spp. were shown to be highly virulent on A. mangium. Contrary, no lesions were observed in the wood of P. caribaea var. hondurensis when inoculated with L. theobromae and L. venezuelensis. However, both species were consistently reisolated from the asymptomatic tissue beyond the inoculation point. This study contributes to a better understand the role that species in the Botryosphaeriaceae play on disease symptoms and dieback of A. mangium and P. caribaea var. hondurensis from plantations in eastern Venezuela.

Endemic and Emerging Pathogens Threatening Cork Oak Trees: Management Options for Conserving a Unique Forest Ecosystem

Cork oak (Quercus suber) forests are economically and culturally intertwined with the inhabitants of the Mediterranean basin and characterize its rural landscape. These forests cover over two million hectares in the western Mediterranean basin and sustain a rich biodiversity of endemisms as well as representing an important source of income derived from cork production. Currently cork oak forests are threatened by several factors including human-mediated disturbances such as poor or inappropriate management practices, adverse environmental conditions (irregular water regime with prolonged drought periods), and attacks of pathogens and pests. All these adverse factors can interact, causing a complex disease commonly known as "oak decline." Despite the numerous investigations carried out so far, decline continues to be the main pathological problem of cork oak forests because of its complex etiology and the resulting difficulties in defining suitable control strategies. An overview of the literature indicates that several pathogenic fungi and oomycota can play a primary role in the etiology of this syndrome. Therefore, the aim of this review is to analyze the recent advances achieved regarding the bio-ecology of the endemic and emerging pathogens that threaten cork oak trees with particular emphasis on the species more directly involved in oak decline. Moreover, the effect of climate change on the host-pathogen interactions, a task fundamental for making useful decisions and managing cork oak forests properly, is considered.

Botryosphaeriaceae species associated with dieback and canker disease of bay laurel in northern California with the description of Dothiorella californica sp. nov

Members of the Botryosphaeriaceae are cosmopolitan fungi that may exist as seemingly innocuous endophytes or as destructive pathogens of numerous woody hosts, including fruit and nut crops, urban ornamental trees and shrubs, and forest trees. Surveys of bay laurel in northern California have revealed symptoms of dieback and branch canker of unknown aetiology. The goals of this study were to identify and clarify the species of Botryosphaeriaceae associated with these symptoms and to confirm their pathogenicity. To understand the role of members of the Botryosphaeriaceae in the dieback and canker disease of bay laurel, 23 isolates were isolated from symptomatic wood. Phylogenetic analyses of ITS, translation elongation factor 1-α, and beta-tubulin revealed three species: Botryosphaeria dothidea, Neofusicoccum nonquaesitum, and the newly described and typified species Dothiorella californica sp. nov. When select isolates were inoculated to 2- to 3-year-old branches of Umbellularia californica in a natural forest, both B. dothidea and N. nonquaesitum were pathogenic with N. nonquaesitum producing the largest lesions at 12- and 18-months post inoculation, respectively, while Do. californica did not cause wood lesions significantly greater than the mock-inoculated controls. This study represents the first attempt to identify and test the pathogenicity of Botryosphaeriaceae species associated with dieback and canker disease of bay laurel in a northern California forest.

Bioactive Secondary Metabolites Produced by the Oak Pathogen Diplodia corticola

Three new lactones and a new fatty acid ester, named sapinofuranones C and D, diplopyrone B, and diplobifuranylone C, respectively, were isolated from Diplodia corticola, together with sphaeropsidins A and C, diplopyrone, diplobifuranylones A and B, diplofuranone A, and the (S,S)-enantiomer of sapinofuranone B. Sapinofuranones C and D, diplopyrone B, and diplobifuranylone C were characterized as (5S)-5-((1,S-1,6-dihydroxyhexa-2,4-dienyl)-dihydrofuran-2-one, 4,5-dihydroxy-deca-6,8-dienoic acid methyl ester, (5S)-5-hydroxy-6-(penta-1,3-dienyl)-5,6-dihydro-pyran-2-one, and 5'-((1R)-1-hydroxyethyl)-2',5'-dihydro-2H-[2,2']bifuranyl-5-one by spectroscopic and chemical methods, respectively. The relative configuration of sapinofuranone C was assigned by X-ray diffraction analysis, whereas its absolute configuration was determined by applying the advanced Mosher's method to its 11-O-p-bromobenzoyl derivative. The same method was used to assign the absolute configuration to C-5 of diplopyrone B and to that of the hydroxyethyl of the side chain of diplobifuranylone C, respectively. The metabolites isolated were tested at 1 mg/mL on leaves of cork oak, grapevine cv. 'Cannonau', and tomato using the leaf puncture assay. They were also tested on tomato cuttings at 0.2, 0.1, and 0.05 mg/mL. Each compound was tested for zootoxic activity on Artemia salina L. larvae. The efficacy of sapinofuranone C and diplopyrone B on three plant pathogens, namely, Athelia rolfsii, Fusarium avenaceum, and Phytophthora nicotianae was also evaluated. In all phytotoxic assays only diplopyrone B was found to be active. It also showed strong inhibition on the vegetative growth of A. rolfsii and P. nicotianae. All metabolites were inactive in the assay performed for the zootoxic activity (A. salina) even at the highest concentration used (200 μg/mL). Diplopyrone B showed a promising antioomycete activity for the control of Phytophthora spp. also taking into account the absence of zootoxic activity.

Caulicolous Botryosphaeriales from Thailand

Members of Botryosphaeriales are commonly encountered as endophytes or pathogens of various plant hosts. The Botryosphaeriaceae represents the predominant family within this order, containing numerous species associated with canker and dieback disease on a wide range of woody hosts. During the course of routine surveys from various plant hosts in Thailand, numerous isolates of Botryosphaeriaceae, including Aplosporellaceae were collected. Isolates were subsequently identified based on a combination of morphological characteristics and phylogenetic analysis of a combined dataset of the ITS and EF1-α gene regions. The resulting phylogenetic tree revealed 11 well-supported clades, correlating with different members of Botryosphaeriales. Other than confirming the presence of taxa such as Lasiodiplodia theobromae, L. pseudotheobromae and Neofusicoccum parvum, new records for Thailand include Pseudofusicoccum adansoniae and P. ardesiacum. Furthermore, four novel species are described, namely Diplodia neojuniperi from Juniperus chinensis, Lasiodiplodia thailandica from Mangifera indica, Pseudofusicoccum artocarpi and Aplosporella artocarpi from Artocarpus heterophyllus, while a sexual morph is also newly reported for L. gonubiensis. Further research is presently underway to determine the pathogenicity and relative importance of these species on different woody hosts in Thailand.

Identification of Botryosphaeriaceae Species Causing Kiwifruit Rot in Sichuan Province, China

Species of Botryosphaeriaceae fungi are important plant pathogens causing cankers, blight, and fruit rot in an extremely wide range of host. In recent years, kiwifruit rot has been a serious problem in Sichuan Province, one of the important kiwifruit production areas of China. Botryosphaeria dothidea has previously been associated with kiwifruit rot but little is known regarding whether other Botryosphaeriaceae genera also constitute kiwifruit rot pathogens in China. Accordingly, diseased fruit were collected from six different areas of Sichuan Province. Based on morphological characteristics, pathogenicity testing, and comparisons of DNA sequences of the internal transcribed spacer, transcription elongation factor 1-α, and β-tubulin genes, 135 isolates of Botryosphaeriaceae were identified as B. dothidea, Lasiodiplodia theobromae, and Neofusicoccum parvum. All of these species were found to cause kiwifruit rot. To understand the infection cycle of kiwifruit rot pathogens, these three species were used to inoculate leaves and shoots of kiwifruit. The results showed that these species could cause spots on leaves and lesions on shoots, producing abundant pycnidia on leaves and shoots surfaces. Moreover, B. dothidea conidia and ascospores from overwintered pycnidia and pseudothecia in kiwifruit orchards in April and August could cause fruit rot and spots on leaves of kiwifruit. Therefore, we concluded that overwintered pycnidia and pseudothecia of B. dothidea in kiwifruit orchards are the primary inoculum for kiwifruit rot, with new pycnidia that develop during the growing season serving as a secondary inoculum. This is the first report of N. parvum and L. theobromae causing kiwifruit rot in China and is also the first report that B. dothidea is able to overwinter as pycnidia and pseudothecia in kiwifruit orchards and serve as the primary inoculum for kiwifruit rot.

Diplopimarane, a 20-nor-ent-pimarane produced by the oak pathogen Diplodia quercivora

In this study a new 20-nor-ent-pimarane, named diplopimarane, was isolated together with sphaeropsidins A (9) and C (10), and (+)-epiepoformin (11) from organic crude extracts of Diplodia quercivora, a recently described oak pathogen originally found on declining Quercus canariensis trees in Tunisia. Diplopimarane was characterized as (1S,2R)-2,8,8-trimethyl-2-vinyl-1,2,3,4,5,6,7,8-octahydrophenanthrene-1,9,10-triol by spectroscopic, X-ray, optical, and chemical methods. It exhibited a wide range of activities including remarkable phytotoxicity on nonhost plants such as tomato cuttings, moderate antifungal activity against important plant pathogens, and moderate zootoxicity against Artemia salina. Its derivatives (2-4 and 6) were also tested for their phytotoxic and zootoxic activities. All these derivatives proved to be active against A. salina at 200 μg/mL, while 2 and 6 were also active on tomato cuttings. The other secondary metabolites (9, 10, and 11) herein reported for D. quercivora exhibited phytotoxic, antifungal, and zootoxic activity. This is the first report on the secondary metabolites secreted in vitro by this oak pathogen that could be key components of its adaptative strategies.

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.

The Botryosphaeriaceae: genera and species known from culture

In this paper we give an account of the genera and species in the Botryosphaeriaceae. We consider morphological characters alone as inadequate to define genera or identify species, given the confusion it has repeatedly introduced in the past, their variation during development, and inevitable overlap as representation grows. Thus it seems likely that all of the older taxa linked to the Botryosphaeriaceae, and for which cultures or DNA sequence data are not available, cannot be linked to the species in this family that are known from culture. Such older taxa will have to be disregarded for future use unless they are epitypified. We therefore focus this paper on the 17 genera that can now be recognised phylogenetically, which concentrates on the species that are presently known from culture. Included is a historical overview of the family, the morphological features that define the genera and species and detailed descriptions of the 17 genera and 110 species. Keys to the genera and species are also provided. Phylogenetic relationships of the genera are given in a multi-locus tree based on combined SSU, ITS, LSU, EF1-α and β-tubulin sequences. The morphological descriptions are supplemented by phylogenetic trees (ITS alone or ITS + EF1-α) for the species in each genus.

TAXONOMIC NOVELTIES

New species - Neofusicoccum batangarum Begoude, Jol. Roux & Slippers. New combinations - Botryosphaeria fabicerciana (S.F. Chen, D. Pavlic, M.J. Wingf. & X.D. Zhou) A.J.L. Phillips & A. Alves, Botryosphaeria ramosa (Pavlic, T.I. Burgess, M.J. Wingf.) A.J.L. Phillips & A. Alves, Cophinforma atrovirens (Mehl & Slippers) A. Alves & A.J.L. Phillips, Cophinforma mamane (D.E. Gardner) A.J.L. Phillips & A. Alves, Dothiorella pretoriensis (Jami, Gryzenh., Slippers & M.J. Wingf.) Abdollahz. & A.J.L. Phillips, Dothiorella thailandica (D.Q. Dai., J.K. Liu & K.D. Hyde) Abdollahz., A.J.L. Phillips & A. Alves, Dothiorella uruguayensis (C.A. Pérez, Blanchette, Slippers & M.J. Wingf.) Abdollahz. & A.J.L. Phillips, Lasiodiplodia lignicola (Ariyawansa, J.K. Liu & K.D. Hyde) A.J.L. Phillips, A. Alves & Abdollahz., Neoscytalidium hyalinum (C.K. Campb. & J.L. Mulder) A.J.L. Phillips, Groenewald & Crous, Sphaeropsis citrigena (A.J.L. Phillips, P.R. Johnst. & Pennycook) A.J.L. Phillips & A. Alves, Sphaeropsis eucalypticola (Doilom, J.K. Liu, & K.D. Hyde) A.J.L. Phillips, Sphaeropsis porosa (Van Niekerk & Crous) A.J.L. Phillips & A. Alves. Epitypification (basionym) - Sphaeria sapinea Fries. Neotypifications (basionyms) - Botryodiplodia theobromae Pat., Physalospora agaves Henn, Sphaeria atrovirens var. visci Alb. & Schwein.

Identification of New Fungal Pathogens of Coast Live Oak in California

A decline of coast live oak (Quercus agrifolia) has been observed throughout southern California. In this study, the identity and pathogenicity of non-Botryosphaeriaceae fungal species consistently recovered from necrotic tissues of branch and bleeding trunk canker samples from these locations were assessed. Species were identified morphologically and by comparison of the complete sequence of the internal transcribed spacer (ITS) of the ribosomal DNA to sequences available in GenBank. Phylogenetic analyses were then conducted using ITS and partial sequences of the β-tubulin and mitochondrial small ribosomal subunit genes for unknown species. Fungi recovered and identified included Fusarium solani, Phaeoacremonium mortoniae, Diatrypella verrucaeformis, and a fungus described herein as Cryptosporiopsis querciphila sp. nov. One-year-old coast live oak seedlings were wound inoculated under controlled conditions to test pathogenicity of the fungal species. Each fungal species was successfully reisolated from necrotic tissue at 70 and 100% for P. mortoniae and all other species, and xylem necrosis was significantly different between all treatments and controls (P < 0.0001 at α = 0.05). Isolates of F. solani were the most aggressive tested. These species represent new records of fungal pathogens of coast live oak in California. Results from the pathogenicity test suggest that these fungi play a role in the decline of southern California coast live oak trees.