Mating type genes in the genus Neofusicoccum: Mating strategies and usefulness in species delimitation

Could Pistachio (Pistacia vera) Be a Suitable Alternative Crop for Olive-Growing Mediterranean Areas Affected by Xylella fastidiosa subsp. pauca ST53?

In the olive-growing areas of Apulia (southern Italy) where Xylella fastidiosa has caused enormous damage, there is a need to identify alternative crops. These could include pistachio (Pistacia vera L.), but it is critical to define the impact of the bacterium on this crop and what are the main phytosanitary threats for this species in the areas where the bacterium is now endemic. Therefore, we started evaluating infections caused by X. fastidiosa, the fungus Neofusicoccum mediterraneum, and other pathogens on four pistachio cultivars ('Kerman', 'Aegina', 'Lost Hills', and 'Napoletana') grown in areas where X. fastidiosa has been present for a long time. X. fastidiosa was detected only in one orchard (incidence: 18% 'Napoletana' and 55% 'Kerman') out of six surveyed orchards, with low bacterium concentration (1.67 to 5.98 × 103 CFU ml-1) and no symptoms. N. mediterraneum was retrieved in three orchards just on the cultivar Kerman but with high incidence (up to 30%) and infection level quantified as molecular severity (6.82 to 7.43); no other pathogens were detected. The N. mediterraneum representative isolates characterized in this study showed similarity with Spanish and Portuguese isolates. A confocal microscope analysis for this host-pathogen association suggested no differences in plant response to fungal aggression between the cultivars Kerman and Aegina, but just lack of latent inoculum in 'Aegina' plants, pointing to a possible nursery origin of the infection. Waiting for additional targeted experiments to clearly define host response of pistachio cultivars to Xylella spp., this study also points at N. mediterraneum as a potential threat to this tree crop new for the area.

Genetic diversity and population structure of Botryosphaeria dothidea and Neofusicoccum parvum on English walnut (Juglans regia L.) in France

Botryosphaeriaceae species are the major causal agents of walnut dieback worldwide, along with Diaporthe species. Botryosphaeria dothidea and Neofusicoccum parvum are the only two Botryosphaeriaceae species associated with this recently emergent disease in France, and little is known about their diversity, structure, origin and dispersion in French walnut orchards. A total of 381 isolates of both species were genetically typed using a sequence-based microsatellite genotyping (SSR-seq) method. This analysis revealed a low genetic diversity and a high clonality of these populations, in agreement with their clonal mode of reproduction. The genetic similarity among populations, regardless of the tissue type and the presence of symptoms, supports the hypothesis that these pathogens can move between fruits and twigs and display latent pathogen lifestyles. Contrasting genetic patterns between N. parvum populations from Californian and Spanish walnut orchards and the French ones suggested no conclusive evidence for pathogen transmission from infected materials. The high genetic similarity with French vineyards populations suggested instead putative transmission between these hosts, which was also observed with B. dothidea populations. Overall, this study provides critical insight into the epidemiology of two important pathogens involved in the emerging dieback of French walnut orchards, including their distribution, potential to mate, putative origin and disease pathways.

Identification and Characterization of Neofusicoccum stellenboschiana in Branch and Twig Dieback-Affected Olive Trees in Italy and Comparative Pathogenicity with N. mediterraneum

For about a decade, olive groves in Apulia (Southern Italy) have been progressively destroyed by Olive Quick Decline Syndrome (OQDS), a disease caused by the bacterium Xylella fastidiosa subsp. pauca (Xfp). Recently, we described an additional wilting syndrome affecting olive trees in that area. The botryosphaeriaceous fungus Neofusicoccum mediterraneum was found associated with the diseased trees, and its high virulence toward olive trees was demonstrated. Given the common features with Branch and Twig Dieback (BTD) of olive tree, occurring in Spain and California, we suggested that the observed syndrome was BTD. During our first survey, we also found a botryosphaeriaceous species other than N. mediterraneum. In the present article, we report the morphological and molecular characterization of this fungal species which we identified as Neofusicoccum stellenboschiana. In the study, we also included for comparison additional N. stellenboschiana isolates obtained from olive trees in Latium and Tuscany region (Central Italy). The occurrence of N. stellenboschiana in olive trees is reported here for the first time in the northern hemisphere. The pathogenicity and virulence were tested in nine inoculation trials, where the Apulian N. stellenboschiana isolate was compared with the isolate from Latium and with the Apulian isolate of N. mediterraneum. Both isolates of N. stellenboschiana proved pathogenic to olive trees. They caused evident bark canker and wood discolouration when inoculated at the base of the stem of two/three-year-old trees and on one-year-old twigs. However, virulence of N. stellenboschiana was significantly lower, though still remarkable, compared with N. mediterraneum in term of necrosis progression in the bark and the wood and capacity of wilting the twigs. Virulence of N. stellenboschiana and N. mediterraneum did not substantially change when inoculations were performed in spring/summer and in autumn, suggesting that these fungal species have the potential to infect and damage olive trees in all seasons. The high thermotolerance of N. stellenboschiana was also revealed with in vitro growth and survival tests. The high virulence of these Botryosphaeriaceae species highlights their contribution in BTD aetiology and the necessity to investigate right away their diffusion and, possibly, the role of additional factors other than Xfp in the general decline of olive groves in Apulia. Hence the importance of assessing the degree of overlap of BTD/Botryosphariaceae with OQDS/Xfp is discussed.

Comparative Genomics Reveals Evolutionary Traits, Mating Strategies, and Pathogenicity-Related Genes Variation of Botryosphaeriaceae

Botryosphaeriaceae, as a major family of the largest class of kingdom fungi Dothideomycetes, encompasses phytopathogens, saprobes, and endophytes. Many members of this family are opportunistic phytopathogens with a wide host range and worldwide geographical distribution, and can infect many economically important plants, including food crops and raw material plants for biofuel production. To date, however, little is known about the family evolutionary characterization, mating strategies, and pathogenicity-related genes variation from a comparative genome perspective. Here, we conducted a large-scale whole-genome comparison of 271 Dothideomycetes, including 19 species in Botryosphaeriaceae. The comparative genome analysis provided a clear classification of Botryosphaeriaceae in Dothideomycetes and indicated that the evolution of lifestyle within Dothideomycetes underwent four major transitions from non-phytopathogenic to phytopathogenic. Mating strategies analysis demonstrated that at least 3 transitions were found within Botryosphaeriaceae from heterothallism to homothallism. Additionally, pathogenicity-related genes contents in different genera varied greatly, indicative of genus-lineage expansion within Botryosphaeriaceae. These findings shed new light on evolutionary traits, mating strategies and pathogenicity-related genes variation of Botryosphaeriaceae.

Neofusicoccum mediterraneum Is Involved in a Twig and Branch Dieback of Olive Trees Observed in Salento (Apulia, Italy)

Olive trees are infected and damaged by Botryosphaeriaceae fungi in various countries. The botryosphaeriaceous fungus Neofusicoccum mediterraneum is highly aggressive and is a major concern for olive groves in Spain and California (USA), where it causes 'branch and twig dieback' characterized by wood discoloration, bark canker, and canopy blight. During surveys of olive groves in Apulia (southern Italy), we noticed that-in some areas-trees were heavily affected by severe branch and twig dieback. In addition, chlorosis and the appearance of red-bronze patches on the leaf preceded the wilting of the foliage, with necrotic leaves persisting on the twigs. Given the severity of the manifestation in zones also subject to olive quick decline syndrome (OQDS) caused by Xylella fastidiosa subsp. pauca, we investigated the etiology and provide indications for differentiating the symptoms from OQDS. Isolation from diseased wood samples revealed a mycete, which was morphologically and molecularly identified as N. mediterraneum. The pathogenicity tests clearly showed that this fungus is able to cause the natural symptoms. Therefore, also considering the low number of tested samples, N. mediterraneum is a potential causal agent of the observed disease. Specifically, inoculation of the twigs caused complete wilting in two to three weeks, while inoculation at the base of the stem caused severe girdling wedge-shaped cankers. The growth rate of the fungus in in vitro tests was progressively higher from 10 to 30 °C, failing to grow at higher temperatures, but keeping its viability even after prolonged exposure at 50 °C. The capacity of the isolate to produce catenulate chlamydospores, which is novel for the species, highlights the possibility of a new morphological strain within N. mediterraneum. Further investigations are ongoing to verify whether additional fungal species are involved in this symptomatology.

First Report of Neofusicoccum parvum Associated with Chestnut Nut Rot in Italy

In autumn 2018, during a study on the pathogens involved in the etiology of chestnut nut rot symptoms observed in three of the main sweet chestnut (Castanea sativa) growing areas in Sardinia (Site 1: 39°56'55"N/09°11'45"E; site 2: 39°58'20"N/09°09'41"E; site 3: 40°52'50"N/09°08'45"E), Gnomoniopsis smithogilvyi was found to be the main causal agent. In addition to G. smithogilvyi, 15 out of 450 nuts processed, yielded on potato dextrose agar (PDA, 39 g/L) at 22°C white colonies with dense aerial mycelium becoming dark grey after 4 to 7 days. Pycnidia were produced within 4 weeks in half-strength PDA incubated at room temperature under natural daylight. The hyaline, ellipsoid to fusiform and aseptate conidia measured 13.4-19.2 × 4.8-7.7 μm (n = 50). All morphological characters matched those reported for Neofusicoccum parvum by Phillips et al. (2013). Identity of isolates was confirmed by DNA sequence analysis of the internal transcribed spacer region (ITS) and part of the translation elongation factor 1-alpha gene (tef1-α). DNA extraction, PCR amplification reactions and DNA sequencing were carried out according to Linaldeddu et al. (2016). In the phylogenetic analysis based on combined ITS and tef1-α gene sequences the N. parvum isolates clustered within two well-supported subclades. In the first subclade (ML bootstrap = 88%) three isolates clustered together with the ex-type culture of N. parvum (CMW9081) while in the second subclade (ML bootstrap = 95%) three isolates clustered together with the ex-type culture of Neofusicoccum algeriense (CBS 137504), a species recently synonymised with N. parvum by Lopes et al. (2016). Sequences of six representative isolates were deposited in GenBank (MK968559-MK968564 and MT010339-MT010344 for ITS and tef1-α, respectively). The pathogenicity of six isolates, belonging to the two haplotypes, was undertaken by inoculating five asymptomatic nuts per isolate. After disinfecting the nut surface with 70% ethanol and removing a piece of shell (5 mm diameter) with a sterile cork borer, the nuts were inoculated with a same-sized agar-mycelium plug cut from the margin of a 5-day-old PDA colony. Ten control nuts were inoculated with a sterile PDA plug applied as described above. Inoculated nuts were kept in thermostat at 22 °C in the dark for 18 days. All nuts inoculated with N. parvum showed light-brown to dark necrosis of kernel associated with loss of tissue consistency. The symptoms were congruent with those observed in nature. All N. parvum isolates were successfully reisolated from all the inoculated nuts, fulfilling Koch's postulates. No lesions were observed on controls. N. parvum is recognized as an emerging plant pathogen worldwide. In particular, several studies report N. parvum as a growing threat to agricultural and forest ecosystems in the Mediterranean area (Larignon et al., 2015; Manca et al., 2020). This is the first report of N. parvum causing chestnut nut rot in Italy.

Bot Gummosis of Lemon (Citrus × limon) Caused by Neofusicoccum parvum

Neofusicoccum parvum, in the family Botryosphaeriaceae, was identified as the causal agent of bot gummosis of lemon (Citrus × limon) trees, in the two major lemon-producing regions in Italy. Gummy cankers on trunk and scaffold branches of mature trees were the most typical disease symptoms. Neofusicoccum parvum was the sole fungus constantly and consistently isolated from the canker bark of symptomatic lemon trees. It was identified on the basis of morphological characters and the phylogenetic analysis of three loci, i.e., the internal transcribed spacer of nuclear ribosomal DNA (ITS) as well as the translation elongation factor 1-alpha (TEF1) and β-tubulin (TUB2) genes. The pathogenicity of N. parvum was demonstrated by wound inoculating two lemon cultivars, 'Femminello 2kr' and 'Monachello', as well as citrange (C. sinensis × Poncirus trifoliata) 'Carrizo' rootstock. In artificial inoculations, the fungus was very aggressive on lemons and weakly virulent on citrange, consistently with symptoms observed in the field as a consequence of natural infections. This is the first report of N. parvum, both in a wide and in a strict taxonomic sense, as a pathogen of lemon in Italy.

Diversity of fungi associated with macroalgae from an estuarine environment and description of Cladosporium rubrum sp. nov. and Hypoxylon aveirense sp. nov

Fungal communities associated with macroalgae remain largely unexplored. To characterize algicolous fungal communities using culture dependent methods, macroalgae were collected from different sampling sites in the Ria de Aveiro estuary, Portugal. From a collection of 486 isolates that were obtained, 213 representative isolates were selected through microsatellite-primed PCR (MSP-PCR) fingerprinting analysis. The collection yielded 33 different genera, which were identified using the ITS region of the rDNA. The results revealed that the most abundant taxa in all collections were Acremonium-like species: Alternaria, Cladosporium, Leptobacillium and Penicillium. The fungal community composition varied with macroalgae species. Through multilocus phylogenetic analyses based on ITS, tub2, tef1-α and actA sequences, in addition to detailed morphological data, we propose Cladosporium rubrum sp. nov. (type strain=CMG 28=MUM 19.39) and Hypoxylon aveirense sp. nov. (type strain=CMG 29=MUM 19.40) as novel species.

Variation in Botryosphaeriaceae from Eucalyptus plantations in YunNan Province in southwestern China across a climatic gradient

The Botryosphaeriaceae accommodates many important pathogens of woody plants, including Eucalyptus. Recently, Botryosphaeriaceae were isolated from diseased plant parts from surveys of Eucalyptus plantations in the YunNan Province, China. The aims of this study were to identify these Botryosphaeriaceae isolates and to evaluate their pathogenicity to Eucalyptus. A total of 166 isolates of Botryosphaeriaceae were obtained from six regions in the YunNan Province, of which 76 were from Eucalyptus urophylla × E. grandis hybrids, 49 from E. globulus trees, and 41 isolates were from other unknown Eucalyptus species or hybrids. Isolates were identified by comparing DNA sequences of the internal transcribed spacer ribosomal RNA locus (ITS), partial translation elongation factor 1-alpha (tef1), β-tubulin 2 (tub2) and DNA-directed RNA polymerase II subunit (rpb2) genes, and combined with their morphological characteristics. Eleven species were identified, including Botryosphaeria fusispora, B. wangensis, Lasiodiplodia pseudotheobromae, Neofusicoccum kwambonambiense, N. parvum, and six novel species described as B. puerensis, N. dianense, N. magniconidium, N. ningerense, N. parviconidium and N. yunnanense. The dominant species across the regions were N. yunnanense, N. parvum and B. wangensis, representing 31.3, 25.3 and 19.9% of the total isolates, respectively. Species diversity and composition changed across the different climatic zones, despite their relatively close geographic proximity and the fact that some of the species have a global distribution. All the Botryosphaeriaceae species were pathogenic to one-year-old plants of an E. urophylla × E. grandis clone and E. globulus seed-derived plants, but showed significant inter- and intra-species variation in aggressiveness amongst isolates. The study provides a foundation for monitoring and management of Botryosphaeriaceae through selection and breeding of Eucalyptus in the YunNan Province of southwestern China.

Revealing the hidden diversity of marine fungi in Portugal with the description of two novel species, Neoascochyta fuci sp. nov. and Paraconiothyrium salinum sp. nov

Fungi are ubiquitous organisms with a wide distribution in almost all ecosystems, including marine environments. Coastal and estuarine ecosystems remain poorly unexplored as fungal habitats, potentially harbouring a hidden diversity with important ecological roles. During an extensive survey of marine fungi in coastal and estuarine Portuguese environments, a collection of 612 isolates was obtained from water, algae, sponges and driftwood. From these, 282 representative isolates were selected through microsatellite-primed PCR (MSP-PCR) fingerprinting analysis, which were identified based on DNA sequence data. The collection yielded 117 taxa from 38 distinct genera, which were identified using DNA sequence analysis. Overall, fungal community composition varied with host/substrate, but the most abundant taxa in the collection were Cladosporium cladosporioides, Penicillium terrigenum, Penicillium brevicompactum and Fusarium equiseti/incarnatum complex. The occurrence of a high fungal diversity harbouring novel species was disclosed. Through a multilocus phylogeny based on ITS, tub2 and tef1-α sequences, in conjunction with morphological and physiological data, we propose Neoascochyta fuci sp. nov. and Paraconiothyrium salinum sp. nov.

Mating-type locus rearrangements and shifts in thallism states in Citrus-associated Phyllosticta species

Currently, eight Phyllosticta species are known to be associated with several Citrus hosts, incorporating diverse lifestyles: while some of them are endophytic (P. capitalensis and P. citribraziliensis), others are pathogenic (P. citriasiana, P. citricarpa, P. citrichinaensis and P. paracitricarpa). Sexual reproduction plays a key role in the interaction between these Phyllosticta species and their Citrus hosts, especially for the spread and persistence of the pathogenic species in the environment. Given this, differences in sexual reproduction strategies could be related to the differences in lifestyles. To evaluate this hypothesis, we characterized the mating-type loci of six Citrus-associated Phyllosticta species from whole genome assemblies. Mating-type genes in the Citrus-associated Phyllosticta species are highly variable in their sequence content, but the genomic locations and organization of the mating-type loci are conserved. Phyllosticta citriasiana, P. citribraziliensis, P. citricarpa and P. paracitricarpa are heterothallic, while P. capitalensis and P. citrichinaensis are homothallic. In addition, the P. citrichinaensis MAT1-2 idiomorph occurs in a separate location from the mating-type locus. Ancestral state reconstruction suggests that homothallism is the ancestral thallism state in Phyllosticta, with a shift to heterothallism in Phyllosticta species that are pathogenic to Citrus. Moreover, the homothallic strategies of P. capitalensis and P. citrichinaensis result from independent evolutionary events, as P. capitalensis locus likely represents the ancestral state, and P. citrichinaensis homothallism has risen through a reversion in a heterothallic ancestor and underwent remodelling events. As the pathogenic species P. citriasiana, P. citricarpa and P. paracitricarpa are heterothallic and incapable of selfing, disease management practices focused in preventing the occurrence of sexual reproduction could assist in the control of Citrus Black Spot and Citrus Tan Spot diseases. This study emphasizes the importance of studying Citrus-Phyllosticta interactions under evolutionary and genomic perspectives, as these approaches can provide valuable information about the association between Phyllosticta species and their hosts, and also serve as guidance for the improvement of disease management practices.

Clonostachys viticola sp. nov., a novel species isolated from Vitis vinifera

A collection of fungal isolates obtained from crop plants, specifically grapevine and blueberry, in Peru were characterised through morphological and DNA sequence analyses of the nuclear ribosomal internal transcribed spacer (ITS), beta-tubulin (tub2) and translation elongation factor 1-alpha (tef-1α) regions. Isolates produced monomorphic and dimorphic conidiophores typical of members of the genus Clonostachys. Single- and multi-locus gene phylogenies confirmed the isolates as representing members of the genus Clonostachys, more closely related to species in the subgenus Bionectria. In phylogenetic analyses the isolates grouped in two separate clades, one corresponding to the species Clonostachys pseudochroleuca and the other one distinct from all known species of the genus Clonostachys. These isolates are recognized as representing a novel species species for which the name Clonostachys viticola is proposed.

Mating genes in Calonectria and evidence for a heterothallic ancestral state

The genus Calonectria includes many important plant pathogens with a wide global distribution. In order to better understand the reproductive biology of these fungi, we characterised the structure of the mating type locus and flanking genes using the genome sequences for seven Calonectria species. Primers to amplify the mating type genes in other species were also developed. PCR amplification of the mating type genes and multi-gene phylogenetic analyses were used to investigate the mating strategies and evolution of mating type in a collection of 70 Calonectria species residing in 10 Calonectria species complexes. Results showed that the organisation of the MAT locus and flanking genes is conserved. In heterothallic species, a novel MAT gene, MAT1-2-12 was identified in the MAT1-2 idiomorph; the MAT1-1 idiomorph, in most cases, contained the MAT1-1-3 gene. Neither MAT1-1-3 nor MAT1-2-12 was found in homothallic Calonectria (Ca.) hongkongensis, Ca. lateralis, Ca. pseudoturangicola and Ca. turangicola. Four different homothallic MAT locus gene arrangements were observed. Ancestral state reconstruction analysis provided evidence that the homothallic state was basal in Calonectria and this evolved from a heterothallic ancestor.

Heterothallism and potential hybridization events inferred for twenty-two yellow morel species

Mating-type genes are central to sexual reproduction in ascomycete fungi and result in the establishment of reproductive barriers. Together with hybridization, they both play important roles in the evolution of fungi. Recently, potential hybridization events and MAT genes were separately found in the Elata Clade of Morchella. Herein, we characterized the MAT1-1-1 and MAT1-2-1 genes of twenty-two species in the Esculenta Clade, another main group in the genus Morchella, and proved heterothallism to be the predominant mating strategy among the twenty-two species tested. Ascospores of these species were multi-nuclear and had many mitochondrial nucleoids. The number of ascospore nuclei might be positively related with the species distribution range. Phylogenetic analyses of MAT1-1-1, MAT1-2-1, intergenic spacer (IGS), and partial histone acetyltransferase ELP3 (F1) were performed and compared with the species phylogeny framework derived from the ribosomal internal transcribed spacer region (ITS) and translation elongation factor 1-alpha (EF1-a) to evaluate their species delimitation ability and investigate potential hybridization events. Conflicting topologies among these genes genealogies and the species phylogeny were revealed and hybridization events were detected between several species. Different evolutionary patterns were suggested for MAT genes between the Esculenta and the Elata Clades. Complex evolutionary trajectories of MAT1-1-1, MAT1-2-1, F1 and IGS in the Esculenta Clade were highlighted. These findings contribute to a better understanding of the importance of hybridization and gene transfer in Morchella and especially for the appearance of reproductive modes during its evolutionary process.

Novel halotolerant species of Emericellopsis and Parasarocladium associated with macroalgae in an estuarine environment

Macroalgae of the genera Fucus, Ulva, and Enteromorpha are typically abundant in estuaries. Endophytic fungi may have beneficial effects on the hosts affecting their ability to cope with stress. They are also a source of biologically active compounds. However, little is known about the endophytic fungi that colonize these macroalgae. Endophytic isolates were obtained from macroalgae from various sites in the estuary Ria de Aveiro (Portugal), as well as from saline water and sponges. Six Acremonium-like species could not be affiliated to any known species. Phylogenetic analyses based on internal transcribed spacer (ITS) region of the ribosomal DNA and β-tubulin (tub2) and actin (act1) genes placed these species in the genera Emericellopsis and Parasarocladium, but distinct from all currently known species. Although sharing morphological characteristics with the most closely related species, these genera differ in micromorphological and molecular characters. Thus, three novel species of Emericellopsis (E. cladophorae, sp. nov., E. enteromorphae, sp. nov., and E. phycophila, sp. nov.) and three novel species of Parasarocladium (P. aestuarinum, sp. nov., P. alavariense, sp. nov., and P. fusiforme, sp. nov.) are proposed.

Neptunomyces aureus gen. et sp. nov. (Didymosphaeriaceae, Pleosporales) isolated from algae in Ria de Aveiro, Portugal

A collection of fungi was isolated from macroalgae of the genera Gracilaria, Enteromorpha and Ulva in the estuary Ria de Aveiro in Portugal. These isolates were characterized through a multilocus phylogeny based on ITS region of the ribosomal DNA, beta-tubulin (tub2) and translation elongation factor 1 alpha (tef1-α) sequences, in conjunction with morphological and physiological data. These analyses showed that the isolates represented an unknown fungus for which a new genus, Neptunomycesgen. nov. and a new species, Neptunomycesaureussp. nov. are proposed. Phylogenetic analyses supported the affiliation of this new taxon to the family Didymosphaeriaceae.

Cloning and analysis of Ophiocordyceps xuefengensis mating type (MAT) loci

The entomopathogenic fungus Ophiocordyceps xuefengensis, a recently described species and identified as the sister taxon of Ophiocordyceps sinensis, is a desirable alternative to O. sinensis. The mating systems of fungi play a vitally important role in the regulation of sexual reproduction and evolution, but the mating type loci of O. xuefengensis were completely unknown. In this study, the mating systems of O. xuefengensis were analyzed. The conserved α-box region of the MAT1-1-1 and HMG-box of MAT1-2-1 were successfully obtained by PCR amplification. The distribution of both mating types in different tissues of wild and cultivated O. xuefengensis growth was detected and analyzed. The results showed that the asci always harbored both mating types, whereas the sclerotium, the stipe and each isolated strain of wild O. xuefengensis always had only one idiomorph, either MAT1-1 or MAT1-2, which confirmed that O. xuefengensis is heterothallic. The MAT1-1 locus of O. xuefengensis harbors MAT1-1-1, MAT1-1-2 and MAT1-1-3, and MAT1-2 contains the MAT1-2-1 gene. Southern blot analysis showed the MAT-1-1-1 and MAT-1-2-1 genes were single-copy in O. xuefengensis. These results will help to understand its life cycle and support artificial cultivation of O. xuefengensis.

Mating System in the Brown Rot Pathogens Monilinia fructicola, M. laxa, and M. fructigena

Monilinia fructicola, M. laxa, and M. fructigena are the most important pathogens responsible for brown rot disease of stone and pome fruits. Information on their mating system and sexual behavior is scant. A mating-type-specific PCR-based assay was developed and applied to 155 Monilinia isolates from 10 countries and 10 different host plants. We showed that single isolates carry only one of two opposite idiomorphs at the MAT1 locus consistent with a heterothallic mating system for all three species. MAT1-1 and MAT1-2 mating types were detected in similar proportions in samples of isolates of each species and hence there do not appear to be genetic obstacles to the occurrence of sexual reproduction in their populations. Inter simple sequence repeat markers suggested that asexual reproduction is prevalent, but that sexual recombination occurs in M. fructicola populations in Italy. The genetic architectures of the MAT1 loci of the three pathogens were analyzed. MAT1-1 and MAT1-2 idiomorphs are flanked upstream and downstream by the APN2 and SLA2 genes and resemble those of Botrytis cinerea and other heterothallic fungi in the family Sclerotiniaceae. Each idiomorph contains a specific couple of genes, MAT1-1-1 (with alpha-box domain) and MAT1-1-5 in MAT1-1, and MAT1-2-1 (with HMG-box domain) and MAT1-2-10 in MAT1-2. Small gene fragments (dMAT1-1-1 and dMAT1-2-1) from the opposite idiomorph were detected close to their flanking regions. Constitutive expression of the four MAT1 genes during vegetative growth was ascertained by transcriptomic analysis (RNA-Seq). Antisense transcription of the MAT1-1-1 and MAT1-2-1 genes and intergenic transcribed regions of the MAT1 locus were detected. These results represent new insights into the mating systems of these three economically-important pathogens which could contribute to improve the knowledge on their population biology.

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.

Using mating-type loci to improve taxonomy of the Tuber indicum complex, and discovery of a new species, T. longispinosum

Black truffles that morphologically resemble Tuber indicum have been known to occur in Japan since 1979. Our previous studies showed that there are two phylotypes of these truffles, both of which fell into the T. indicum complex (hereinafter "Tuber sp. 6" and "Tuber sp. 7"). However, their taxonomic treatment is still unclear. In this study, we conducted morphological and phylogenetic analyses for a total of 52 specimens from Japan (16 Tuber sp. 6 and 13 Tuber sp. 7), China (10 T. himalayense and 8 T. indicum), and Taiwan (5 T. formosanum). We compared ascospore ornamentation, size, distribution of asci with average number of spores per ascus, spine size and shape of the Japanese specimens with their allied taxa. For phylogenetic analysis, we sequenced two mating loci (MAT1-1-1 and MAT1-2-1) and three commonly used loci (ITS, β-tubulin, and TEF1-α). Three distinct lineages were recognized by phylogenetic analyses based on the sequences of the two mating-related loci and three independent loci. The Tuber sp. 6 sequences clustered with those of T. himalayense and T. formosanum, and there was no clear difference in morphology among them. Tuber sp. 7 formed a distinct lineage in each phylogram. The specimens tended to have five-spored asci more frequently than other allied species and could be characterized as having ascospore ornamentation with longer spines and narrower spine bases. We therefore described Tuber sp. 7 as a new species (T. longispinosum), and treat Tuber sp. 6 and T. formosanum as synonyms of T. himalayense.

Evolution of the mating types and mating strategies in prominent genera in the Botryosphaeriaceae

Little is known regarding mating strategies in the Botryosphaeriaceae. To understand sexual reproduction in this fungal family, the mating type genes of Botryosphaeria dothidea and Macrophomina phaseolina, as well as several species of Diplodia, Lasiodiplodia and Neofusicoccum were characterized from whole genome assemblies. Comparisons between the mating type loci of these fungi showed that the mating type genes are highly variable, but in most cases the organization of these genes is conserved. Of the species considered, nine were homothallic and seven were heterothallic. Mating type gene fragments were discovered flanking the mating type regions, which indicates both ongoing and ancestral recombination occurring within the mating type region. Ancestral reconstruction analysis further indicated that heterothallism is the ancestral state in the Botryosphaeriaceae and this is supported by the presence of mating type gene fragments in homothallic species. The results also show that at least five transitions from heterothallism to homothallism have taken place in the Botryosphaeriaceae. The study provides a foundation for comparison of mating type evolution between Botryosphaeriaceae and other fungi and also provides valuable markers for population biology studies in this family.

Botryosphaeriaceae from Eucalyptus plantations and adjacent plants in China

The Botryosphaeriaceae is a species-rich family that includes pathogens of a wide variety of plants, including species of Eucalyptus. Recently, during disease surveys in China, diseased samples associated with species of Botryosphaeriaceae were collected from plantation Eucalyptus and other plants, including Cunninghamina lanceolata, Dimocarpus longan, Melastoma sanguineum and Phoenix hanceana, which were growing adjacent to Eucalyptus. In addition, few samples from Araucaria cunninghamii and Cedrus deodara in two gardens were also included in this study. Disease symptoms observed mainly included stem canker, shoot and twig blight. In this study, 105 isolates of Botryosphaeriaceae were collected from six provinces, of which 81 isolates were from Eucalyptus trees. These isolates were identified based on comparisons of the DNA sequences of the internal transcribed spacer regions and intervening 5.8S nrRNA gene (ITS), and partial translation elongation factor 1-alpha (tef1), β-tubulin (tub), DNA-directed RNA polymerase II subunit (rpb2) and calmodulin (cmdA) genes, the nuclear ribosomal large subunit (LSU) and the nuclear ribosomal small subunit (SSU), and combined with their morphological characteristics. Results showed that these isolates represent 12 species of Botryosphaeriaceae, including Botryosphaeria fusispora, Cophinforma atrovirens, Lasiodiplodia brasiliense, L. pseudotheobromae, L. theobromae and Neofusicoccum parvum, and six previously undescribed species of Botryosphaeria and Neofusicoccum, namely B. pseudoramosa sp. nov., B. qingyuanensis sp. nov., B. wangensis sp. nov., N. hongkongense sp. nov., N. microconidium sp. nov. and N. sinoeucalypti sp. nov. Aside from B. wangensis, C. atrovirens and N. hongkongense, the other nine Botryosphaeriaceae species were isolated from Eucalyptus trees in South China. Botryosphaeria fusispora (26 % of the isolates from Eucalyptus) is the dominant species, followed by L. pseudotheobromae (23 % of the isolates from Eucalyptus). In addition to species found on Eucalyptus trees, we also found B. pseudoramosa on M. sanguineum; B. wangensis on C. deodara; C. atrovirens on D. longan; L. theobromae on C. lanceolata, D. longan and P. hanceana; and N. hongkongense on A. cunninghamii. Pathogenicity tests showed that the 12 species of Botryosphaeriaceae are pathogenic to three Eucalyptus clones and that Lasiodiplodia species are the most aggressive. The results of our study suggest that many more species of the Botryosphaeriaceae remain to be discovered in China. This study also provides confirmation for the wide host range of Botryosphaeriaceae species on different plants.

Diversity in the Botryosphaeriales: Looking back, looking forward

The Botryosphaeriales are amongst the most widespread, common and important fungal pathogens of woody plants. Many are also known to exist as endophytes in healthy plant tissues. This special issue highlights a number of key themes in the study of this group of fungi. In particular, there have been dramatic taxonomic changes over the past decade; from one family to nine (including two in this special issue) and from 10 to 33 genera known from culture. It is also clear from many studies that neither morphology nor single locus sequence data are sufficient to define taxa. This problem is exacerbated by the increasing recognition of cryptic species and hybrids (as highlighted for the first time in this special issue). It is futile that management strategies, including quarantine, continue to rely on outdated taxonomic definitions and identification tools. This is especially true in light of growing evidence that many species continue to be moved globally as endophytes in plants and plant products. A well defined natural classification and an extensive collection of tools to study the Botryosphaeriaceae, including a growing number of genomes, now provide a springboard for a much deeper exploration of their biology, biogeography and host associations.