Talaromyces minioluteus: New Postharvest Fungal Pathogen in Serbia

Pathogen Eradication in Garlic in the Phytobiome Context: Should We Aim for Complete Cleaning?

Global food production is challenged by plant pathogens that cause significant crop losses. Fungi, bacteria, and viruses have long threatened sustainable and profitable agriculture. The danger is even higher in vegetatively propagated horticultural crops, such as garlic. Currently, quarantine, rouging infected plants, and control of natural vectors are used as the main means of disease and pest control in garlic crops. Agricultural biotechnology, meristem-tip culture, and cryotherapy offer solutions for virus eradication and for the multiplication of 'clean stocks', but at the same time, impact the symbiotic and beneficial components of the garlic microbiome. Our research involves the first metatranscriptomic analysis of the microbiome of garlic bulb tissue, PCR analyses, and a biological assay of endophytes and pathogens. We have demonstrated that in vitro sanitation methods, such as shoot tip culture or cryotherapy can alter the garlic microbiome. Shoot tip culture proved ineffective in virus elimination, but reduced bacterial load and eliminated fungal infections. Conversely, cryotherapy was efficient in virus eradication but demolished other components of the garlic microbiome. Garlic plants sanitized by cryotherapy exhibited a lower survival rate, and a longer in vitro regeneration period. The question arises whether total eradication of viruses, at the expense of other microflora, is necessary, or if a partial reduction in the pathogenic load would suffice for sanitized garlic production. We explore this question from both scientific and commercial perspectives.

Isolation and identification of antagonistic Bacillus amyloliquefaciens HSE-12 and its effects on peanut growth and rhizosphere microbial community

The HSE-12 strain isolated from peanut rhizosphere soil was identified as Bacillus amyloliquefaciens by observation of phenotypic characteristics, physiological and biochemical tests, 16S rDNA and gyrB gene sequencing. In vitro experiments showed that the strain possessed biocontrol activity against a variety of pathogens including Sclerotium rolfsii. The strain has the ability to produce hydrolytic enzymes, as well as volatile organic compounds with antagonistic and probiotic effects such as ethyleneglycol and 2,3-butanediol. In addition, HSE-12 showed potassium solubilizing (10.54 ± 0.19 mg/L), phosphorus solubilization (168.34 ± 8.06 mg/L) and nitrogen fixation (17.35 ± 2.34 mg/g) abilities, and was able to secrete siderophores [(Ar-A)/Ar × 100%: 56%] which promoted plant growth. After inoculating peanut with HSE-12, the available phosphorus content in rhizosphere soil increased by 27%, urease activity increased by 43%, catalase activity increased by 70% and sucrase activity increased by 50% (p < 0.05). The dry weight, fresh weight and the height of the first pair of lateral branches of peanuts increased by 24.7, 41.9, and 36.4%, respectively, compared with uninoculated peanuts. In addition, compared with the blank control, it increased the diversity and richness of peanut rhizosphere bacteria and changed the community structure of bacteria and fungi. The relative abundance of beneficial microorganisms such as Sphingomonas, Arthrobacter, RB41, and Micromonospora in rhizosphere soil was increased, while the relative abundance of pathogenic microorganisms such as Aspergillus, Neocosmospora, and Rhizoctonia was decreased.

Genomic Sequence Resource of Talaromyces albobiverticillius, the Causative Pathogen of Pomegranate Pulp Rot Disease

Talaromyces albobiverticillius, a prominent pathogen responsible for pomegranate pulp rot disease, inflicts significant damage on Punica granatum L. Besides its pathogenicity, this fungus possesses the potential to produce substantial amounts of red pigments, making it promising for industrial applications. This study presents the genome annotation of T. albobiverticillius field strain Tp-2, isolated from pomegranates. The genome assembly, generated through a combination of Oxford Nanopore and Illumina sequencing reads, yielded a high-quality assembly with 14 contigs, featuring an N50 length of 4,594,200 bp. The complete genome of strain Tp-2 spans 38,354,882 bp, with a GC content of 45.78%. Importantly, the assembly exhibits remarkable integrity, with 98.3% of complete Benchmarking Universal Single-Copy Orthologs validating genome completeness. Genome prediction analysis reveals the presence of 10,380 protein-coding genes. To our knowledge, this study is the first report on the genome sequence of T. albobiverticillius, offering valuable insights into its genetic variation and molecular mechanisms of pigment production.

Two Novel Species of Talaromyces Discovered in a Karst Cave in the Satun UNESCO Global Geopark of Southern Thailand

Karst caves are oligotrophic environments that appear to support a high diversity of fungi. Studies of fungi in Thailand’s caves are limited. During a 2019 exploration of the mycobiota associated with soil samples from a karst cave, namely, Phu Pha Phet in the Satun UNESCO Global Geopark in Satun Province, southern Thailand, two previously undescribed fungi belonging to Talaromyces (Trichocomaceae, Eurotiales, Eurotiomycetes) were studied using a polyphasic approach combining phenotypic and molecular data. Based on datasets of four loci (ITS, BenA, CaM, and RPB2), phylogenetic trees of the section Trachyspermi were constructed, and two new species—Talaromyces phuphaphetensis sp. nov. and T. satunensis sp. nov.—phylogenetically related to T. subericola, T. resinae, and T. brasiliensis, are described. Detailed descriptions and illustrations of the new species are provided. This study increases the number of cave-dwelling soil fungi discovered in Thailand’s Satun UNESCO Global Geopark, which appears to be a unique environment with a high potential for discovering fungal species previously undescribed.

New Insights into Chemical and Biological Properties of Funicone-like Compounds

Funicone-like compounds are a homogeneous group of polyketides that, so far, have only been reported as fungal secondary metabolites. In particular, species in the genus Talaromyces seem to be the most typical producers of this group of secondary metabolites. The molecular structure of funicone, the archetype of these products, is characterized by a γ-pyrone ring linked through a ketone group to a α-resorcylic acid nucleus. This review provides an update on the current knowledge on the chemistry of funicone-like compounds, with special emphasis on their classification, occurrence, and diverse biological activities. In addition, their potential relevance as mycotoxins is discussed.

Polyphasic identification of decay agents of lemon fruits in Serbia

Lemon fruits are an important source of vitamin C, potassium, folate, carotenoids, polyphenols, coumarins and terpenes. These lemon compounds have antioxidant and anti-inflammatory properties which have beneficial effects on human health. This research aimed to elucidate the etiology of blue and green molds detected on lemon fruits in Serbia. Using integrative identification approach, the obtained isolates were characterized from morphological, physiological, molecular, phylogenetic and pathological aspects. Colony growth and morphology were examined on Czapek yeast autolysate agar (CYA), Malt extract agar (MEA) and Creatine sucrose agar (CREA), and on CYA at two additional incubation temperatures (5 and 37 ?C). For molecular identification, ITS and partial ?-tubulin (BenA) genes were sequenced. Phylogenetic relationships were investigated using maximum-likelihood method. A pathogenicity test was carried out and the possible difference in pathogenicity among isolates was assessed with analysis of variance (ANOVA) and subsequent Tukey?s test. Four species were identified: Penicillium expansum, Penicillium digitatum, Penicillium polonicum and Talaromyces rugulosus. All four species proved to be pathogenic on lemon fruits, producing symptoms similar to those observed on naturally infected fruits. The results of this study are the first records of the beforementioned Penicillium/ Talaromyces species as postharvest pathogens on lemon fruits in Serbia and the first world report of T. rugulosus as phytopathogenic on the same host.

Re-Evaluation of the Taxonomy of Talaromyces minioluteus

Talaromyces minioluteus belongs to the section Trachyspermi, has a worldwide distribution and has been found on various substrates, especially on various (stored) food commodities and indoor environments. This species is phenotypically and phylogenetically closely related to T. chongqingensis and T. minnesotensis. The phylogenetic and morphological analyses of 37 strains previously identified as T. chongqingensis, T. minnesotensis and T. minioluteus revealed that this clade incudes eight species: the accepted species T. chongqingensis, T. minnesotensis and T. minioluteus, the newly proposed species T. calidominioluteus, T. africanus and T. germanicus, and the new combinations T. gaditanus (basionym Penicillium gaditanum) and T. samsonii (basionym Penicillium samsonii). In this study, we give insight of the phylogenetic relationships and provide detailed descriptions of the species belonging to this clade. Macromorphological features, especially colony growth rates, texture and conidial colors on agar media, are important characters for phenotypic differentiation between species.

Penicillium and Talaromyces Species as Postharvest Pathogens of Pear Fruit (Pyrus communis) in Serbia

Pears are one of the oldest and the third most important fruit species grown in temperate regions. They are consumed because of their nutritional and health benefits, in fresh form or as various processed products. This article resolves the etiology of the Penicillium-like mold symptoms on pear fruits in Serbia. Samples of pear fruits with blue mold and other Penicillium-like mold symptoms were collected in Serbia from 2016 to 2019, from four storages. The recovered isolates were identified and characterized according to a polyphasic approach. Morphological and physiological analyses were performed on three media and five temperatures, respectively. Four loci (internal transcribed spacer, beta-tubulin, calmodulin, and DNA-dependent RNA polymerase II second largest subunit) were used for sequencing, genetic identification, and phylogenetic analyses. The results of the identification by conventional and molecular methods were in agreement, and they revealed that the obtained isolates belong to five species: Penicillium crustosum, P. expansum, P. italicum, Talaromyces minioluteus, and T. rugulosus. In a pathogenicity test, P. crustosum, P. expansum, T. minioluteus, and T. rugulosus produced decay on artificially inoculated pear fruits, and P. italicum induced tissue response lesions. The results of this study are the first reports of T. minioluteus and T. rugulosus as postharvest pear pathogens. Also, these are the first world records of T. minioluteus, T. rugulosus, and P. italicum on fruits of European pear. Furthermore, this is the first finding of P. crustosum, P. expansum, P. italicum, T. minioluteus, and T. rugulosus on pear fruit in Serbia.

Fungal communities in bat guano, speleothem surfaces, and cavern water in Madai cave, Northern Borneo (Malaysia)

The island of Borneo is a global biodiversity hotspot. However, its limestone caves are one of its least-studied ecosystems. We report for the first time the fungal species richness, diversity and abundance from Madai cave, situated in north-eastern Borneo. Environmental samples from inside the cave environment were collected (guano, speleothem, and cavern water) via opportunistic sampling. The dilution method was performed for isolation of fungi. Morphological characterisation and molecular analysis of the ITS region were utilised for the identification of isolates. Fifty-five pure cultures of fungi were attained, comprising 32 species from 15 genera, eight orders, and two divisions, Ascomycota and Basidiomycota. Ascomycetes dominated the fungal composition, accounting for 53 (96%) out of 55 total isolates. Penicillium spp. accounted for more than 47.1% of fungal abundance in all sample types. However, Aspergillus spp. had the highest occurrence rate, being isolated from all environmental samples except one. Purpureocillium lilacinum was isolated most frequently, appearing in five separate samples across all three substrates. Annulohypoxylon nitens, Ganoderma australe, Pyrrhoderma noxium, and Xylaria feejeensis were discovered and reported for the first time from the cave environment. This study provides additional data for further research on the mycoflora of Sabah’s various ecosystems, especially limestone caves.

Microbiome Status of Cider-Apples, from Orchard to Processing, with a Special Focus on Penicillium expansum Occurrence and Patulin Contamination

Patulin is a secondary metabolite produced primarily by the fungus Penicillium expansum, responsible for the blue mold disease on apples. It is found in apple products including apple cider when apple juice is added after fermentation. In the present study, two hundred and twenty-five cider-apples of the variety “Bedan”, cultivated in Brittany in France, were sampled from the orchard during harvesting until the storage step, right before processing. The patulin analysis on these samples reported a low contamination at the orchard and a significantly higher-level of contamination in the cider-apples starting from the transporting bin. The percentage of positive samples increased from 6% to 47% after 12 h in the harvesting bin before transporting and reached 95% after 24 h of transporting, decreasing then to 69% at the end of the storage. Penicillium expansum was quantified on the surface of apples using real-time PCR and was observed to be mostly consistent between the harvest and post-harvest steps. It was detected on average, on the surface of 85% of all sampled apples with a mean value around 2.35 × 10⁶Penicillium expansum DNA/g of apple. Moreover, the changes in the fungal and bacterial epiphytic microbiota in the different steps were studied using a metabarcoding approach. The alpha and beta diversity analysis revealed the presence of unique and more diverse bacterial and fungal communities on the surface of apples picked from the orchard compared to the rest of the sampling steps. Potential indigenous biological control agents were identified on the surface of sampled apples. Future perspective includes developing actions of prevention and control of the contamination by Penicillium expansum during the harvest and along the various critical post-harvest stages before transformation in a sustainable development concern.

Molecular phylogeny, identification and pathogenicity of Rhizopus oryzae associated with root rot of mulberry in India

AIMS

Root rot caused by a group of fungi is a serious disease in mulberry. This study aims to identify and characterize Rhizopus oryzae and other fungal species associated with root rot of mulberry in India.

METHODS AND RESULTS

Rotted root samples were collected from the mulberry gardens from four states of Southern India. The majority of the isolates identified were R. oryzae, and others were saprophytic fungi, less abundant to occasional. Two methods of inoculations were tested to confirm the pathogenicity of the selected isolates and R. oryzae was found to be pathogenic on susceptible mulberry genotypes RC2 and SRDC-1. Multi gene phylogenetic analyses using the internal transcribed spacer region (ITS), actin (ACT) and translation elongation factor 1-α (TEF), identified the isolates as R. oryzae. Additionally, Ovatospora brasiliensis, Amesia nigricolor, Gongronella butleri, Myrmecridium schulzeri, Scedosporium boydii, Graphium euwallacea, Clonostachys rosea andTalaromyces spp. were also identified.

CONCLUSION

This study revealed the existence of eleven species of fungi including the first report of R. oryzae and the occurrence of weak pathogens or saprophytes that are associated with the root rot of mulberry in India.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first report of R. oryzae causing Rhizopus rot of mulberry in India. Moreover, the occurrence of saprophytes associated with root rot of mulberry was identified. Further studies should focus more on the ability of these species to generate secondary metabolites and extracellular lytic enzymes as they are beneficial for the management of root rot disease.