Multilocus Phylogeography of the Tuber mesentericum Complex Unearths Three Highly Divergent Cryptic Species

Tuber mesentericum is an edible European black truffle, apparently easy to recognize, but showing a high degree of genetic variability. In this study, we performed an integrative taxonomic assessment of the T. mesentericum complex, combining a multilocus phylogeographic approach with morphological analyses, and including authentic specimens of Vittadini, and Berkeley and Broome. We performed maximum likelihood phylogenetic analyses, based on single and concatenated gene datasets (ITS rDNA, β-tubulin, elongation factor 1-α), and including all available sequences from previous studies. Phylogenetic analyses consistently recovered three reciprocally monophyletic and well-supported clades: clade I, with a wide range across Europe; clade II, specimens collected mainly in the Iberian, Italian, and Balkan peninsulas; and clade III, specimens collected almost exclusively in central Italy. Genetic distance between clades ranged from 10.4% to 13.1% at the ITS region. We also designed new primer pairs specific for each phylogenetic lineage. Morphology of spores, asci, and peridium were investigated on specimens representing the three lineages. Macro- and micromorphological analyses of ascomata revealed only a few, but not diagnostic, differences between the three phylogenetic lineages, thus, confirming that they are morphologically cryptic. By studying authentic specimens of Vittadini, and Berkeley and Broome, it was possible to identify the three clades as T. mesentericum, Tuber bituminatum, and Tuber suave sp. nov., and to designate an epitype for T. mesentericum s.s. and a lectotype for T. bituminatum. Future investigations on volatile organic compound (VOC) composition are needed to define the aroma repertoires in this species complex.

First Report of Black Spot Caused by Neoscytalidium dimidiatum on Sisal in Guangxi, China

Sisal (Agave sisalana Perrine) is an important hard fiber crop that is widely planted in Guangxi, Guangdong, Hainan, Yunnan, and Fujian provinces, China. In July 2019, a new leaf disease of sisal with a disease incident of about 36% was found in Guangxi (Fig.1a~d). The oval or circular black lesions were 2.3 cm to 15.9 cm in length and 1.6 cm to 5.5 cm in width on both sides of the diseased leaves. The central part of the lesions was slightly hollow. The lesions continuously enlarged and ultimately penetrated the leaves. Reddish brown and dark mucus was secreted from the lesions. The junction of lesions and healthy parts was reddish brown to yellow. The diseased leaf fiber and mesophyll tissues were reddish brown and necrotic. Fresh leaf yield was reduced about 30% by the disease, and fiber quality was significantly compromised every year in Guangxi. Six kinds of fungi distinguished by their morphology, size and color of the colonies were isolated from diseased leaf tissues of 60 sisal plants sampled from five different farms in Guangxi. Isolate JMHB1 was isolated at a rate of 95.67%. The isolate JMHB1 was initially white with dense and hairy aerial mycelium, gradually turning dark grey to olive green on PDA (Fig. 2). Conidia, arthrospores, and chlamydospores were observed on PDA in culture (Fig. 3). The conidia formed arthric chains, disarticulating, cylindrical-truncate, oblong-obtuse to doliiform, colorless and transparent, zero- to one-septate, and averaging 4.4 to 13.8 µm × 2.2 to 5.6 µm (n=100). Arthrospores were short columnar, pigmented and transparent, single or formed arthric chains, averaging 5.5 to 17.9 µm × 2.1 to 3.5 µm (n=100). Chlamydospores were dark brown, round or oval, averaging 4.5 to 9.6 µm × 4.5 to 8.6 µm (n=100). Pathogenicity testing was conducted by inoculating 3-year-old healthy sisal plants with PDA plugs (5 × 5 mm) on which the fungus had grown for 5 days. Nine healthy plants were wounded on the leaves with a sterile needle, and mycelial plugs were placed on the wounds, covered with sterile moist cotton, and wrapped with parafilm. Nine control plants were wounded and treated with PDA plugs as the negative control. The test was repeated three times. All treated plants were kept in a greenhouse at ~28 ℃ and 40% RH. After 5 days, only leaves inoculated with isolate JMHB1 showed lesions similar to symptoms observed in the field (Fig.1e~f). The fungus was re-isolated from all nine diseased plants, and no symptoms were observed on the leaves of control plants. Molecular identification of the fungus was made by PCR amplification of the internal transcribed spacer (ITS) region of rDNA, EF1-α gene and β-tubulin gene using primers ITS1/ITS4 (White et al. 1990), EFl-728F/EF1-986R (Carbone and Kohn 1999), TUB2Fd/TUB4Rd (Aveskamp et al. 2009) respectively. The ITS (MT705646), EF1-α (MT733516) and β-tubulin (MT773603) sequences of JMHB1 were similar to the ITS (AY819727), EF1-α (EU144063) and β-tubulin (KF531800) sequences of the epitype of Neoscytalidium dimidiatum (CBS 499.66) with 100%, 99.65% and 99.02% identity, respectively. Based on pathogenicity testing, morphological characteristics, and molecular identification, the pathogen of sisal causing black spot was identified as N. dimidiatum (Penz.) Crous & Slippers (Crous et al. 2006). To our knowledge, this is the first report of black spot caused by N. dimidiatum on sisal in China. Sisal is the main economic crop in arid and semi-arid areas that is widely planted in several provinces of southern China. The serious occurrence of the disease caused by N. dimidiatum has greatly affected the development of sisal industry and local economic income in China. Identification of the pathogen of the disease is of great significance to guide disease control, increase farmers' income and promote the development of sisal industry. References: Aveskamp, M. M., et al. 2009. Mycologia, 101: 363. https://doi.org/10.3852/08-199. Carbone, I., and Kohn, L. M. 1999. Mycologia, 91:553. https://doi.org/10.1080/00275514.1999. 12061051. Crous, P. W., et al. 2006. Stud. Mycol. 55:235. https://doi.org/10.3114/sim.55.1.235. White, T. J., et al. 1990. PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, Page 315. doi.org/10.1002/mrd.1080280418. Supplemental photographs: Fig. 1 Symptoms of sisal black spot disease a, b, c, d showed symptoms in the field, e and f were symptoms after inoculating Neoscytalidium dimidiatum JMHB1. a, c, and e were the front of the lesions, b, d, and f were the back of the lesions. Fig. 2 Primary colony (a) and old colony (b) of Neoscytalidium dimidiatum JMHB1 Fig. 3 Arthrospores (a), conidia and chlamydospores (b) of Neoscytalidium dimidiatum JMHB1.

First Report of Dieback Caused by Lasiodiplodia pseudotheobromae on Ormosia pinnata in China

Ormosia pinnata (Lour.) Merr. is an important tree used for landscape and plant recovery of barren slopes in China. During an investigation of plant disease on landscape trees in 2018, a dieback was observed on O. pinnata trees in Guangzhou, Guangdong Province, China. Symptoms were characterized by initial dryness of the twigs and eventual death of the whole branch of the tree. Isolations from symptomatic branches yielded 13 isolates including two main morphotypes. Pathogenicity tests showed that isolate GDOP1 from Type I caused dieback of O. pinnata. Based on morphological characteristics and molecular analysis of the internal transcribed spacer rDNA (ITS1-5.8S-ITS2) and partial sequence of the translation elongation factor 1α (EF1-α), the fungus causing dieback on O. pinnata was identified as Lasiodiplodia pseudotheobromae. This is the first report of L. pseudotheobromae infecting O. pinnata in the world.

Analysis of phylogeny, distribution, and pathogenicity of Botryosphaeriaceae species associated with gummosis of Anacardium in Brazil, with a new species of Lasiodiplodia

Netto, M. S. B., Lima, W. G., Correia, K. C., da Silva, C. F. B., Thon, M., Martins, R. B., Miller, R. N. G., Michereff, S. J., and Câmara, M. P. S. 2016. Analysis of phylogeny, distribution, and pathogenicity of Botryosphaeriaceae species associated with gummosis of Anacardium in Brazil, with a new species of Lasiodiplodia. We identified Botryosphaeriaceae species associated with gummosis on Anacardium in Brazil. Isolates were sampled and identified on the basis morphology and phylogeny, through analysis of a partial translation elongation factor 1-α sequence, ribosomal DNA internal transcribed spacers, and β-tubulin gene sequence. Ten taxa were identified, namely, Lasiodiplodia brasiliense, L. euphorbicola, L. gonubiensis, L. iraniensis, L. jatrophicola, L. gravistriata sp. nov., L. pseudotheobromae, L. theobromae, Neofusicoccum batangarum, and Pseudofusicoccum stromaticum. Lasiodiplodia theobromae has been previously reported in cashew and is the most prevalent species observed. All the other species are reported here for the first time on this host. All species of Botryosphaeriaceae were pathogenic on detached green cashew shoots. Differences in aggressiveness were observed among the species, with N. batangarum, L. iraniensis, L. jatrophicola, and L. gravistriata characterized as the most aggressive species, whilst L. euphorbicola and L. pseudotheobromae were identified as the least aggressive.

Characterization and phylogeny of Isaria spp. strains (Ascomycota: Hypocreales) using ITS1-5.8S-ITS2 and elongation factor 1-alpha sequences

The elongation factor 1-alpha (EF1-α) and the internal transcribed spacer (ITS) regions ITS1 and ITS2 (ITS1-5.8S-ITS2) sequences were used to characterize and to identify Isaria isolates from Argentina, Mexico, and Brazil, as well as to study the phylogenetic relationships among these isolates and other related fungi from the order Hypocreales. The molecular characterization, which was performed by PCR-RFLP of EF1-α and ITS1-5.8-ITS2 genes, was useful for resolving representative isolates of Isaria fumosorosea, Isaria farinosa, and Isaria tenuipes and to confirm the taxonomic identity of fungi from Argentina, Mexico, and Brazil. The phylogenetic analyses showed three clades corresponding to three families of Hypocreales. The genus Isaria was confirmed as polyphyletic and in family Cordycipitaceae, Isaria species were related to anamorphic species of Beauveria, Lecanicillium, and Simplicillium and to teleomorphic Cordyceps and Torrubiella. Therefore, EF1-α and ITS1-5.8S-ITS2 genes were found to be powerful tools for improving the characterization, identification, and phylogenetic relationship of the Isaria species and other entomopathogenic fungi.

Resolving the Diaporthe species occurring on soybean in Croatia

Diaporthe (anamorph = Phomopsis) species are plant pathogens and endophytes on a wide range of hosts including economically important crops. At least four Diaporthe taxa occur on soybean and they are responsible for serious diseases and significant yield losses. Although several studies have extensively described the culture and morphological characters of these pathogens, their taxonomy has not been fully resolved. Diaporthe and Phomopsis isolates were obtained from soybean and other plant hosts throughout Croatia. Phylogenetic relationships were determined through analyses of partial translation elongation factor 1-alpha (EF1-α) gene and ITS nrDNA sequence data. By combining morphological and molecular data, four species could be distinguished on soybeans in Croatia. Diaporthe phaseolorum is described in this study and its synonyms are discussed. Diaporthe phaseolorum var. caulivora is raised to species status and the name Diaporthe caulivora is introduced to accommodate it. A species previously known as Phomopsis sp. 9 from earlier studies on sunflower, grapevine, rooibos and hydrangea is reported for the first time on soybean, and is formally described as Diaporthe novem. The well-known soybean pathogen Phomopsis longicolla was also collected in the present study and was transferred to Diaporthe longicolla comb. nov. The presence of these species on herbaceous hosts raises once more the relevance of weeds as reservoirs for pathogens of economically important plants.

Resolving the phylogenetic and taxonomic status of dark-spored teleomorph genera in the Botryosphaeriaceae

Species in the Botryosphaeriaceae are common plant pathogens and saprobes found on a variety of mainly woody hosts. Teleomorphs typically have hyaline, aseptate ascospores. However, some have been reported with brown ascospores and their taxonomic status is uncertain. A multi-gene approach (SSU, ITS, LSU, EF1-alpha and beta-tubulin) was used to resolve the correct phylogenetic position of the dark-spored 'Botryosphaeria' teleomorphs and related asexual species. Neodeightonia and Phaeobotryon are reinstated for species with brown ascospores that are either 1-septate (Neodeightonia) or 2-septate (Phaeobotryon). Phaeobotryosphaeria is reinstated for species with brown, aseptate ascospores that bear an apiculus at either end. The status of Sphaeropsis is clarified and shown to be the anamorph of Phaeobotryosphaeria. Two new genera, namely Barriopsis for species having brown, aseptate ascospores without apiculi and Spencermartinsia for species having brown, 1-septate ascospores with an apiculus at either end are introduced. Species of Dothiorella have brown, 1-septate ascospores and differ from Spencermartinsia in the absence of apiculi. These six genera can also be distinguished from one another based on morphological characters of their anamorphs. Although previously placed in the Botryosphaeriaceae, Dothidotthia, was shown to belong in the Pleosporales, and the new family Dothidotthiaceae is introduced to accommodate it.