First report of Irpex rosettiformis causing white root rot in avocado trees in Michoacán, México.

In México, avocado production is an important economic source. In the last season it generated $ 3. 27 billion USD of foreign currency in the country. Irpex spp. are wood decay fungi. In the period 2019-2022, in the state of Michoacán (19°13' N; 101°55' W), México, basidiomes of Irpex sp. were observed on the base of trunks and crowns of 5-years-old and older avocado (Persea americana) trees. The trees exhibited disease symptoms that included white root rot, leaf yellowing, small leaves, branch diebacks, generalized defoliation, apical flaccidity, abundant but small sun burnt fruits due to the lack of foliage, and after 2-4 years of first disease appearance, the infected trees died. In the place where fungus was established, abundant white and cottony mycelium was formed, which caused trees decay. The incidence of the disease in the sampled orchards was estimated to be 30% per ha with 350 - 400 trees, which was determined through a simple sampling design focused on trees with signs and symptoms of the disease due to the phytopathogen. Samples of infected tissue (roots and stems) and fungal basidiomes were collected from 90 trees (5-6 per orchard). The symptomatic avocado trees studied were randomly selected from 17 orchards. For the fungal macroscopic characterization, the synoptic keys described by Gilbertson and Ryvarden (1986) and by Largent (1973) were used. The samples showed typical structures corresponding to Irpex sp., including rosettes, annual basidiomes, a system of monomitic hyphae, and subglobose basidiospores. In vitro fungal isolation from basidiomes and infected tree tissues was done according to the protocol of Agrios (2004). The fungal strains were maintained on PDA at 28 °C. At 16 days of incubation the colonies were opaque, whitish with fluffy and corky mycelium. Microscopic analysis of the fungus showed typical yellowish spores, with an ellipsoid shape of 3-4 x 4-5.5 µm (50 accounted structures per isolate [N=19]) and basidia of 20-25 x 4.5-5.5 µm (n=20 basidiomes). For molecular characterization, two molecular markers were used, the internal transcribed spacer rDNA-ITS1 5.8 rDNA-ITS2 (ITS; White et al. 1990) and the large ribosomal subunit (LSU; Vilgalys and Hester 1990). The PCR reaction was performed as described by Martínez-González et al. (2017). The consensus sequences were compared with those deposited in the NCBI-GenBank, using the BLASTN 2.2.19 tool (Zhang et al. 2000), the samples showed 99% match with the species, Irpex rosettiformis. GenBank accession numbers of the submitted isolates are summarized in supplementary Table 4. To test Koch's postulates, 3-months old avocado plants grown in greenhouse conditions were inoculated (n = 10 per each isolate [N= 19]) on the roots with 3 g of I. rosettiformis mycelium. The experiment was done twice with 20 non-inoculated plants as control. After 67 days, basidiomes (50 x 70 x 1.5 mm in average) were observed where the disease incidence was >77%, with subsequent tree decline. The pathogen was re-isolated in vitro in PDA and its identity was confirmed by morphological characteristics of mycelium. This work shows that I. rosettiformis is not only a wood decay fungus, but also a phytopathogen, the causative agent of white root rot disease in P. americana var. drymifolia, cultivar 'Hass', which establishes a precedent for monitoring and preventing its proliferation to other regions in the American continent and the world where nursery avocado seedlings are exported.

New Ascomycetes from the Mexican Tropical Montane Cloud Forest.

The tropical montane cloud forest is the most diverse and threatened vegetation type in Mexico. In the last decade, the number of described Ascomycetes species has notably increased, reaching more than 1300 species. This study describes six new species based on their molecular and morphological characteristics. Our results suggest that Mexico has the highest number of described species in the Neotropics. However, many other Mexican lineages still need to be described.

Elaphomycescastilloi (Elaphomycetaceae, Ascomycota) and Entolomasecotioides (Entolomataceae, Basidiomycota), two new sequestrate fungi from tropical montane cloud forest from south Mexico.

Two new species of sequestrate fungi are described from south Mexico based on morphological and molecular evidences. Here we describe Elaphomycescastilloi characterized by the yellowish mycelial mat, dull blue gleba and ascospores of 9.7-11.5 µm; Entolomasecotioides is characterized by the secotioid basidiomata, sulcate, pale cream pileus, and basidiospores of 7-13 × 5-9 µm. Both species grow in montane cloud forest under Quercus sp. in the state of Chiapas, Mexico. Descriptions, photographs, and multilocus phylogeny for both species are presented.

Novelties in Macrofungi of the Tropical Montane Cloud Forest in Mexico.

The tropical montane cloud forest in Mexico is the most diverse and threatened ecosystem. Mexican macrofungi numbers more than 1408 species. This study described four new species of Agaricomycetes (Bondarzewia, Gymnopilus, Serpula, Sparassis) based on molecular and morphological characteristics. Our results support that Mexico is among the most biodiverse countries in terms of macrofungi in the Neotropics.

Two new species of Trichoglossum (Geoglossaceae, Ascomycota) from south Mexico.

Two new species of Trichoglossum are described from south Mexico based on morphological and molecular evidence. Trichoglossumcaespitosum is characterized by the caespitose ascomata, rough and coiled paraphyses and the ascospores with 9-11 septa. Trichoglossumtropicale is characterized by the capitate ascomata, clavate and straight paraphyses and the ascospores with 10-12 septa. Both species grow in the tropical forests of the Yucatán peninsula. Here we provide descriptions and photographs for these species, together with a phylogenetic analyses based on the DNA sequences of nuc rDNA (ITS region and 28S gene) and a comparative table for the species known for America.

Three new species of Rhytidhysteron (Dothideomycetes, Ascomycota) from Mexico.

The genus Rhytidhysteron is characterised by forming navicular to apothecial hysterothecia, exposing the green, yellow, orange, red, vinaceous or black colours of the hymenium which generally releases pigments in the presence of KOH. The exciple is smooth or striated, the asci bitunicate and ascospores have 1-5 transverse septa. To date, twenty-six Rhytidhysteron species have been described from the Tropics. The present study aims to describe three new species in the Neotropics of Mexico based on molecular methods and morphological features. Illustrations and a taxonomic key are provided for all known species of this genus. Rhytidhysteroncozumelense from the Isla Cozumel Biosphere Reserve, R.esperanzae from the Sierra Juárez, Oaxaca and R.mesophilum from the Sierra Madre Oriental, Hidalgo are described as new species. With the present study, the number of species of Rhytidhysteron known from Mexico is now increased to eight.

Purpureocillium roseum sp. nov. A new ocular pathogen for humans and mice resistant to antifungals.

BACKGROUND: Infectious keratitis is the main cause of preventable blindness worldwide, with about 1.5-2.0 million new cases occurring per year. This inflammatory response may be due to infections caused by bacteria, fungi, viruses or parasites. Fungal keratitis is a poorly studied health problem. OBJECTIVES: This study aimed to identify a new fungal species by molecular methods and to explore the possible efficacy of the three most common antifungals used in human keratitis in Mexico by performing in vitro analysis. The capacity of this pathogen to cause corneal infection in a murine model was also evaluated. METHODS: The fungal strain was isolated from a patient with a corneal ulcer. To identify the fungus, taxonomic and phylogenetic analyses (nrDNA ITS and LSU data set) were performed. An antifungal susceptibility assay for amphotericin B, itraconazole and voriconazole was carried out. The fungal isolate was used to develop a keratitis model in BALB/c mice; entire eyes and ocular tissues were preserved and processed for histopathologic examination. RESULTS AND CONCLUSION: This fungal genus has hitherto not been reported with human keratitis in Mexico. We described a new species Purpurecillium roseum isolated from corneal infection. P roseum showed resistance to amphotericin B and itraconazole and was sensitive to voriconazole. In vivo study demonstrated that P roseum had capacity to developed corneal infection and to penetrate deeper corneal tissue. The global change in fungal infections has emphasised the need to develop better diagnostic mycology laboratories and to recognise the group of potential fungal pathogens.

Identification and biofilm development by a new fungal keratitis aetiologic agent.

BACKGROUND: In recent years, human keratitis caused by fungal plant pathogens has become more common. Biofilm is a structure that confers adaptations and virulence to fungi in keratitis. Neoscytalidium spp. are phytopathogenic and recently have been recognised as a human pathogen, using biofilm formation as a virulence factor. OBJECTIVES: The aim of this study was isolation, identification (at the species level) and characterisation of a new fungal keratitis agent. PATIENTS/METHODS: The fungus was isolated from a 67-year-old male patient with a corneal ulcer. Biofilm formation and structure were evaluated by colorimetric methods and microscopy. To identify the fungus, morphological characteristics were examined and a phylogenetic analysis was performed. RESULTS AND CONCLUSIONS: We report the identification of a fungus, a member of the genus Neoscytalidium which is associated with human keratitis. Phylogenetic analysis and morphological observations on conidiogenous cells, which occur only in arthric chains in aerial mycelium and the coelomycetous synasexual morph is absent, identified a new species, Neoscytalidium oculus sp. nov. The fungus formed biofilm at a concentration of 1 × 106  conidia/mL, during 96 hours of incubation at 37°C, and also manifested haemolysis and melanin production. This is the first report in Latin America of a new species of Neoscytalidium from a clinical isolate has been identified.

Fomitiporia cupressicola sp. nov., a parasite on Cupressus arizonica, and additional unnamed clades in the southern USA and northern Mexico, determined by multilocus phylogenetic analyses.

Fomitiporia cupressicola sp. nov., found in living Cupressus arizonica, is described on the basis of several collections originating from a high altitude forest in the northern Sierra Madre Occidental, Mexico. The species forms a monophyletic clade, basal to a larger lineage comprising species originating mainly from temperate to Mediterranean areas of the northern hemisphere. The phylogenetic approach in Fomitiporia also revealed multiple unnamed clades within the F. robusta complex in the southern USA and northern Mexico, representing potential species. The status of the F. robusta complex in North America is discussed briefly.