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Soil is one of the main reservoirs of fungi. The aim of this study was to study the richness of ascomycetes in a set of soil samples from Mexico and Spain. Fungi were isolated after 2% w/v phenol treatment of samples. In that way, several strains of the genus Penicillium were recovered. A phylogenetic analysis based on internal transcribed spacer (ITS), beta-tubulin (BenA), calmodulin (CaM), and RNA polymerase II subunit 2 gene (rpb2) sequences showed that four of these strains had not been described before. Penicillium melanosporum produces monoverticillate conidiophores and brownish conidia covered by an ornate brown sheath. Penicillium michoacanense and Penicillium siccitolerans produce sclerotia, and their asexual morph is similar to species in the section Aspergilloides (despite all of them pertaining to section Lanata-Divaricata). P. michoacanense differs from P. siccitolerans in having thick-walled peridial cells (thin-walled in P. siccitolerans). Penicillium sexuale differs from Penicillium cryptum in the section Crypta because it does not produce an asexual morph. Its ascostromata have a peridium composed of thick-walled polygonal cells, and its ascospores are broadly lenticular with two equatorial ridges widely separated by a furrow. All four new species are xerophilic. Despite the genus Penicillium containing more than 480 known species, they are rarely reported as xerophilic. [ABSTRACT FROM AUTHOR]

The diseases found in Pinus patula, a species present in the forest area of Puebla, Mexico cause foliage loss and damage to trees and we consider that fungi could be involved. The objective of the current investigation was to study the nutrients of the soil and the fungi associated with the lesions on the needles of Pinus patula in Tetela de Ocampo, Puebla, Mexico. It was found that the nitrogen, phosphorus and potassium content of the soils associated with pine, as well as the organic matter, were poor. In addition, we performed chemical, physical and biological analyses on soils from the study site. We isolated forty-five fungi from the lesions on the needles. The identification of twelve of them was both morphological and molecular by sequence analysis of the ITS1-ITS2 gene. The identified fungi included Alternaria alternata, Annulohypoxylon stygium, Botryosphaeria dothidea, Curvularia lunata, Curvularia pseudobrachyspora, Curvularia spicifera, Curvularia trifolii, Daldinia eschscholtzii, Daldinia sp. Diplodia sapinea, Lophodermium indianum and Myrmaecium rubricosum. We concluded that P. patula is affected by nutritional deficiency as well as by the presence of phytopathogenic fungi. [ABSTRACT FROM AUTHOR]

The research was carried out in the state of Nuevo León, Mexico, during 2018, with the aim of isolating and identifying strains of soil microorganisms and evaluating their antagonistic capacity in vitro against citrus pathogens Lasiodiplodia theobromae and Fomitopsis meliae. For the isolation of the microorganisms, 17 rhizosphere samplings were carried out in different locations and types of vegetation; the samples were heat treated and spread by extension in the potato dextrose agar culture medium added with 0.3% yeast extract and 0.3% malt extract (PDLMA). The isolates obtained were preliminarily evaluated by observation and growth comparison. Of 70 isolates, 15 presented antagonistic activity, which showed inhibition percentages of 39-91%. The actinomycete strains M4 R and M1-101, and the fungus M104 (Penicillium citrinum) caused 84, 91 and 85% inhibition respectively against L. theobromae and 83, 91 and 91% respectively against F. meliae. Isolation of bacteria was achieved, actinomycetes and fungi from the soil capable of inhibiting the growth of L. theobromae and F. meliae fungi causing regressive citrus death. [ABSTRACT FROM AUTHOR]

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Mexico is the fifth largest producer of papaya worldwide and has recently reported problems with mucoralean fungi in this crop. These fungi are considered saprophytes in the soil and are ubiquitous in nature. In this work, they were isolated from soil in regions of intensive papaya cultivation in Mexico. Collections were made in the states of Colima, Oaxaca and Veracruz in Apr 2016. A total of 72 mucorales fungal isolates was obtained and morphologically characterized and then molecular characterization (28S ribosomal region) of 25 representative isolates was carried out. Phylogenetic analysis of the sequences confirmed the presence of the species Gilbertella persicaria , Rhizopus oryzae , Rhizopus stolonifer , Mucor circinelloides and Mucor hiemalis , which cause soft rot in papaya fruits, therefore, spores of these fungi found in the orchard soils can be considered as a constant source of contamination that affects healthy fruits. Additionally, Choanephora cucurbitarum , Mucor ellipsoideus , Rhizopus homothallicus , Rhizopus microsporus , Rhizopus schipperae , Lichteimia ramosa , Gongronella butleri , Cunninghamella bertholletiae and Cunninghamella blakesleeana were identified which are considered to have agricultural, biotechnological and medical importance. [ABSTRACT FROM AUTHOR]

The objectives of the present study were to isolate Beauveria bassiana strains from cattle farm soils, analyze the phylogenetic relationships among the fungal strains isolated from these soils, and determine the acaricidal effect of B. bassiana isolates on engorged Rhipicephalus microplus tick strains resistant or susceptible to chemical acaricides. Six strains of B. bassiana were obtained and isolated from cattle farm soils in the Mexican tropics using the Galleria bait method, and their acaricidal effect was assessed against 2 populations of R. microplus ('Media Joya' chemical acaricide-resistant strain or 'CLAR' chemical acaricide-susceptible strain) using the adult immersion test. The BbV03 strain produced 86.7% and 60% mortality in resistant and susceptible ticks on day 20, respectively, whereas the BbV04 strain produced 66.7% and 53.5% mortality in resistant and susceptible ticks on day 20, respectively. The BbV03 and BbV04 strains reduced egg laying on both R. microplus populations. There was no statistical difference in the acaricidal effect of B. bassiana strains among chemical acaricide-susceptible or -resistant R. microplus populations ( P > 0.05). The BbV03 strain was the most virulent against R. microplus with an LC50 of 2 × 107 and LC99 of 7 × 108 conidia/ml. We found that the 6 B. bassiana isolated clustered in the same clade with other previously reported B. bassiana strains (from GenBank) but were separated into 3 different sub-clades. This study shows that some B. bassiana strains are a promising coadjuvant alternative for biological tick control, including tick populations that are resistant to chemical acaricides. Beauveria bassiana is present in the pastures of tropic cattle farms, and there are genetic variations between B. bassiana strains living in this ecosystem that might play an important role in the natural control of R. microplus in cattle farm paddocks. [ABSTRACT FROM AUTHOR]

Plant facilitative interactions may persist in the long term when there are benefits for the interacting adult plants. Whereas persistent benefits for adult nurse plants have been demonstrated, the long-term benefits derived by adult facilitated plants have been largely unexplored. We hypothesize that common mycorrhizal networks (CMNs) can provide a pathway through which nurse species can benefit adult facilitated plants persistently. We specifically test whether nitrogen can be transferred from nurse plants to their adult facilitated plants, and evaluate to which extent CMNs mediate the transfer. We selected 32 adult individuals of 6 facilitated plant species growing in 15 vegetation patches in a Mexican desert. We treated some vegetation patches with fungicide and left others as controls. Then, we labeled the nurse plants with 15 N-enriched urea and quantified the amount of 15 N transferred to their adult facilitated plants. We expected a greater 15 N transfer to facilitated individuals growing in vegetation patches with intact CMNs than in those treated with fungicide. Facilitated plants growing in patches with intact CMNs showed on average a greater increment in their foliar δ 15 N (i.e. difference between post-labeling–pre-labeling) than those in patches treated with fungicide. Our results provide evidence that CMNs enhance nitrogen transfer among adult plants, thus providing a potential mechanism contributing to the long-term persistence of plant facilitative associations. [ABSTRACT FROM AUTHOR]

Abstract: Approximately four-fifths of the land area of Baja California (BC) in Mexico are occupied by arid and semiarid soils, the mycobiota of which is virtually uncharacterized. In the first culture-independent study of the mycobiota of BC, we collected soil from five different locations in the region and constructed a Dikarya-specific gene library for the ITS region of nuclear ribosomal DNA. Clones were analyzed by RFLP, were sequenced for phylogenetic analyses, and diversity and similarity indices were calculated. The ascomycete Penicillium dipodomyicola was the most frequent fungus found in soil at the most arid location studied, and the basidiomycete Coprinellus radians was the most frequent at the location receiving the highest rainfall. Other frequent members of the soil mycobiota were identified as Alternaria spp., Ceratobasidium sp., Coniozyma leucospermi, Nematoctonus robustus, Penicillium griseofulvum, Tulostoma kotlabae and uncultured members of the Dikarya. Several sequences were identified as those of uncultured fungi, one of which was previously reported from other hot deserts. Arid soils and the transitional zones between arid and semiarid soils had the most similar fungal diversity, with the former soils having a community from which basidiomycetes were absent, and the soil receiving the highest precipitation having a community dominated by basidiomycetes. [Copyright &y& Elsevier]

Abstract: Coccidioidomycosis is an important human fungal infection of American deserts and nearby semi-arid regions with highly endemic areas distributed along the United States-Mexico border. Despite the increasing incidence in the last 20yr, reports of positive isolations of the causal agent, Coccidioides spp. from environmental samples have been scarce. To resolve this paradox, it is extremely important to first identify the fundamental ecological niche of this fungus. Soil samples (n =90) including those from heteromyids’ active burrows, latrines and other mammals’ dens were collected using an oriented sampling method from areas of Baja California, Mexico previously predicted as putative endemic “hotspots”. The total genomic DNA obtained from the collected samples was subjected to a nested PCR followed by a diagnostic PCR designed to amplify the internal transcribed spacer (ITS) 2 region of Coccidioides spp. From the 42 amplicons obtained and sequenced (37 from Valle de las Palmas (VDP) and five from San Jose de la Zorra (SJZ)), 32 were confirmed to belong to Coccidioides spp. No Coccidioides spp. were found in soils collected in Ensenada. VDP and SJZ have different soil characteristics but share a Mediterranean climate having less than 250mm of precipitation per year, as well as a dry period of at least 6months. The development of Coccidioides spp. is probably related to the structure of the microbial population adapted to these conditions in the semi-arid-mediterranean ecotone. [Copyright &y& Elsevier]