Lactarius Species Research Articles

Microbiological quality of some fresh wild edible mushrooms

Fresh mushrooms are an ideal medium for microbial growth because they have high moisture content and a neutral pH. Mushrooms are hand-harvested and exposed to ambient conditions until commercialised in many cases. These characteristics limit their post-harvest shelf life to a few days. Unlike other fresh products, the studies on the microbiological profile of fresh mushrooms are limited. In public, Lactarius species are known as "çıntar, melki, kanlıca, termite, menne specifically used in Türkiye. These mushrooms usually grow naturally during the autumn. They are collected by locals and sold in public markets and along the roadside. In this study, the microbiological quality of wild edible Lactarius species sold in local marketplaces in the province of Muğla was determined. The results are in the ranges 6.10-8.83 log CFU/g for total mesophilic aerobic bacteria, <1.00-5.57 log CFU/g for lactic acid bacteria, 3.10-7.76 log CFU/g for total yeast, <1.00-3.93 log CFU/g for total mould, <1.00-4.74 log CFU/g for Staphylococcus aureus, <0.30-5.07 log MPN/g for total coliform and <0.30-5.07 log MPN/g for faecal coliform. The samples' pH and titratable acidity values were 6.82-7.54 and 0.005-0.020%, respectively.

Phenolic Content, Antibacterial and Antioxidant Potential of Several Edible Agaricomycetes Mushrooms Sold in Public Bazaar in Bolu, Turkey

Edible mushrooms are important natural foods that have been used since ancient times due to their delicious taste, high nutritional value, and various biological activities. In this study, antibacterial (against 10 different human pathogens) and antioxidant potentials (free radical scavenging activity and total phenol-flavonoid content) of 13 different wild-growing and the most popular edible mushrooms (Lactarius salmonicolor, L. deliciosus, L. volemus, L. piperatus, Boletus edulis, Marasmius oreades, Agaricus campestris, Tricholoma terreum, Hydnum repandum, Coprinus comatus, Ramaria sp., Cantharellus cibarius, and Pleurotus ostreatus) sold in a public bazaar in Bolu-Turkey were evaluated. Strong antibacterial capacities were observed with all tested Lactarius species, as well as M. oreades, A. campestris, T. terreum, H. repandum, and Ramaria sp. Significant antibacterial potentials of T. terreum and C. comatus against Staphylococcus epidermidis, Serratia marcescens, and Proteus vulgaris were observed for the first time. H. repandum strongly inhibited all tested Gram-positive bacteria (Staphylococcus aureus, S. epidermidis, and Streptococcus pyogenes). It was remarkable to reveal strong growth inhibition of M. oreades against S. aureus (29.33 ± 1.11 mm) for the first time. The highest total phenolic content was revealed with L. delicious (193.42 ± 0.77 mg GAE/g dw and 198 ± 0.79 mg TAE/g dw), while L. salmonicolor had the highest total flavonoid content (358.33 ± 15.27 mg CE/g dw). B. edulis demonstrated the strongest antioxidant activity with the lowest IC50 value (4.48 ± 0.04 μg/mL). Moreover, L. deliciosus and M. oreades also had high antioxidant potential with the lowest IC50 values (4.76 ± 0.01 μg/mL and 4.77 ± 0.02 μg/mL, respectively). Total phenolic contents of tested mushrooms were highly correlated with their antioxidant capacities. L. delicious is the most well-known and the most delicious mushroom sold in Bolu's public bazaar. The obtained results for this mushroom were notable in terms of the greatest total phenol-flavonoid content and strong antioxidant capability. The antioxidant capacity and polyphenol content of L. deliciosus, M. oreades, H. repandum, A. campestris, and B. edulis, as well as their antibacterial activity, were quite outstanding, and our findings demonstrated the importance of these mushrooms as nutraceutical products.

Comparative genomics reveals a dynamic genome evolution in the ectomycorrhizal milk-cap (Lactarius) mushrooms.

Ectomycorrhizal fungi play a key role in forests by establishing mutualistic symbioses with woody plants. Genome analyses have identified conserved symbiosis-related traits among ectomycorrhizal fungal species, but the molecular mechanisms underlying host specificity remain poorly known. We sequenced and compared the genomes of seven species of milk-cap fungi (Lactarius, Russulales) with contrasting host specificity. We also compared these genomes with those of symbiotic and saprotrophic Russulales species, aiming to identify genes involved in their ecology and host specificity. The size of Lactarius genomes is significantly larger than other Russulales species, owing to a massive accumulation of transposable elements and duplication of dispensable genes. As expected, their repertoire of genes coding for plant cell wall-degrading enzymes is restricted, but they retained a substantial set of genes involved in microbial cell wall degradation. Notably, Lactarius species showed a striking expansion of genes encoding proteases, such as secreted ectomycorrhiza-induced sedolisins. A high copy number of genes coding for small secreted LysM proteins and Lactarius-specific lectins were detected, which may be linked to host specificity. This study revealed a large diversity in the genome landscapes and gene repertoires within Russulaceae. The known host specificity of Lactarius symbionts may be related to mycorrhiza-induced species-specific genes, including secreted sedolisins.

Anticancer and apoptotic effects of a polysaccharide extract isolated from Lactarius chrysorrheus Fr. in HepG2 and PANC-1 cell lines

Mushrooms are widely used in many cultures for nutritional and health benefits. The Lactarius species is found in the Aegean region of Turkey. Lactarius chrysorrheus Fr. is a wild mushroom that contains a milky juice. In this study, we investigated the in vitro cytotoxic potential and apoptotic effect of the polysaccharide extract prepared from L. chrysorrheus by water extraction and alcohol precipitation using the tetrazolium MTT dye assay, annexin V staining, wound healing and colony formation, and qRT-PCR. The molecular weights of three peaks observed in HPLC chromatograms were calculated as 1869.9, 3043.92 and 16821.47 Da. The extract exhibited cytotoxic activity at 72 h, with an IC50 value of 296.42 ?g/mL in HepG2 and 444.43 ?g/mL in PANC-1 cells; the extract that was tested on the normal HEK293 cell line exhibited no cytotoxicity. Further, L. chrysorrheus upregulated the expression of CASPASE 3 and CASPASE 9 while downregulating B-cell lymphoma 2 (BCL-2) and B-cell lymphoma-extra large (Bcl-xL) genes, and inhibited cell migration and colony formation in HepG2 and PANC-1 cells. This study provides new insight into the use of the polysaccharide from L. chrysorrheus in the development of novel anticancer agents.

Conservation Status of Milkcaps (Basidiomycota, Russulales, Russulaceae), with Notes on Poorly Known Species

Mycological conservation has finally come of age. The increasingly recognized crucial role played by fungi in ecosystem functioning has spurred a wave of attention toward the status of fungal populations across the world. Milkcaps (Lactarius and Lactifluus) are a large and widespread group of ectomycorrhizal basidiomycetes; besides their ecological relevance, many species of milkcaps are of socio-economic significance because of their edibility. We analysed the presence of milkcaps in fungal Red Lists worldwide, ending up with an impressive list of 265 species assessed in various threat categories. Lactarius species are disproportionally red-listed with respect to Lactifluus (241 versus 24 species). Two species of Lactarius (L. maruiaensis and L. ogasawarashimensis) are currently considered extinct, and four more are regionally extinct; furthermore, 37 species are critically endangered at least in part of their distribution range. Several problems with the red-listing of milkcaps have been identified in this study, which overall originate from a poor understanding of the assessed species. Wrong or outdated nomenclature has been applied in many instances, and European names have been largely used to indicate taxa occurring in North America and Asia, sometimes without any supporting evidence. Moreover, several rarely recorded and poorly known species, for which virtually no data exist, have been included in Red Lists in some instances. We stress the importance of a detailed study of the species of milkcaps earmarked for insertion in Red Lists, either at national or international level, in order to avoid diminishing the value of this important conservation tool.

Transcriptome Profiling Reveals Differential Gene Expression of Secreted Proteases and Highly Specific Gene Repertoires Involved in Lactarius-Pinus Symbioses.

Ectomycorrhizal fungi establish a mutualistic symbiosis in roots of most woody plants. The molecular underpinning of ectomycorrhizal development was only explored in a few lineages. Here, we characterized the symbiotic transcriptomes of several milkcap species (Lactarius, Russulales) in association with different pine hosts. A time-course study of changes in gene expression during the development of L. deliciosus–Pinus taeda symbiosis identified 6 to 594 differentially expressed fungal genes at various developmental stages. Up- or down-regulated genes are involved in signaling pathways, nutrient transport, cell wall modifications, and plant defenses. A high number of genes coding for secreted proteases, especially sedolisins, were induced during root colonization. In contrast, only a few genes encoding mycorrhiza-induced small secreted proteins were identified. This feature was confirmed in several other Lactarius species in association with various pines. Further comparison among all these species revealed that each Lactarius species encodes a highly specific symbiotic gene repertoire, a feature possibly related to their host-specificity. This study provides insights on the genetic basis of symbiosis in an ectomycorrhizal order, the Russulales, which was not investigated so far.

Characterization of Japanese Lactarius section deliciosi ectomycorrhizae: Toward the use of mycorrhizae for taxonomy and expansion of available cultures

Abstract We described the ectomycorrhizae (ECM) of the Japanese Lactarius section Deliciosi species L. akahatsu, L. hatsudake, L. laeticolor, and L. subindigo with the aim of promoting the use of mycorrhizae for taxonomy and expansion of available cultures. Lactarius tottoriensis (sect. Lactarius) was also included as a comparator. The ECM of the four species of sect. Deliciosi showed orange laticifers and plectenchymatous mantles, whereas those of L. tottoriensis showed white laticifers and pseudoparenchymatous mantles. The ECM of L. hatsudake and L. subindigo showed complex rhizomorphs with thicker walls and more developed vessel-like hyphae compared to the other three species. Cystidium-like cells were rarely found on the mantles of L. laeticolor and L. subindigo. Fungal cultures of the five Lactarius species from their ECM were morphologically characterized. Cultures produced laticifers on agar medium, but the five species showed different growth rates. Rhizomorphs of L. hatsudake and L. subindigo in cultures showed a similar morphology to their ECM. Molecular phylogenetic analyses of cultures from the ECM demonstrated that they were of the targeted Lactarius species and suggested the need for taxonomic studies of L. hatsudake, L. subindigo, and L. tottoriensis at the species and section levels.

Virus population structure in the ectomycorrhizal fungi Lactarius rufus and L. tabidus at two forest sites in Southern Finland

Lactarius fungi belong to the Russulaceae family and have an important ecological role as ectomycorrhizal symbionts of coniferous and deciduous trees. Two Lactarius species, L. tabidus and L. rufus have been shown to harbor bisegmented dsRNA viruses belonging to an unclassified virus group including the mutualistic Curvularia thermal tolerance virus (CThTV). In this study, we characterized the first complete genome sequences of these viruses designated as Lactarius tabidus RNA virus 1 (LtRV1) and Lactarius rufus RNA virus 1 (LrRV1), both of which included two genome segments of 2241 and 2049 bp. We also analyzed spatial distribution and sequence diversity of the viruses in sixty host strains at two forest sites, and showed that the viruses are species-specific at sites where both host species co-occur. We also found that single virus isolates inhabited several different conspecific host strains, and were involved in persistent infections during up to eight years.

Taxonomic revision of the genus Lactarius (Russulales, Basidiomycota) in Korea

The genus Lactarius Pers. (Russulales) is a cosmopolitan group of Basidiomycota that forms ectomycorrhizal relationships primarily with both deciduous and coniferous trees. Although the genus has been well-studied in Europe and North America, only fragmentary researches have been carried out on Asian species. In particular, the distribution of Lactarius species in South Korea is poorly understood due to insufficient morphological descriptions and a lack of DNA sequence data. In addition, the misuse of European and North American names has added to confusion regarding the taxonomy of Asian Lactarius species. In this study, the diversity of Lactarius in South Korea was evaluated by employing both morphological and phylogenetic approaches. A multi-locus phylogenetic analysis of 729 Lactarius specimens collected between 1960 and 2017 was performed using the internal transcribed spacer (ITS) region, partial nuclear ribosomal large subunit (nrLSU), partial second largest subunit of RNA polymerase II (rpb2), and minichromosome maintenance complex component 7 (mcm7). 49 Lactarius species were identified in three Lactarius subgenera: L. subg. Russularia (17 spp.), L. subg. Lactarius (22 spp.), and L. subg. Plinthogalus (10 spp.). Among them, 28 Lactarius species were identified as new to science, while just 17 were previously described Lactarius species. Four of the taxa remain un-named due to paucity of materials. A key to Korean Lactarius species, molecular phylogenies, a summary of diversity, and detailed description are provided.

Two Lactarius species (subgenus Plinthogalus) in ectomycorrhizal association with tropical Quercus trees in eastern Mexico

ABSTRACTTwo species of Lactarius are documented from fragments of tropical lowland oak forest in central Veracruz. Lactarius trichodermoides, described here as new, was found in association with Quercus sapotifolia and Lactarius subplinthogalus with Quercus glaucescens. Both Lactarius species were identified morphologically and supported by phylogenetic analyses of nuc rDNA internal transcribed spacers (ITS1-5.8S-ITS2) and D1–D2 domains of nuc 28S rDNA sequences. Confirmation of mycobionts in ectomycorrhizal (ECM) associations was verified by molecular identification of ECM root tips. Detailed macroscopic and microscopic descriptions and photographs and illustrations of basidiomes and ectomycorrhizas are presented. The new binomial Lactarius chiangmaiensis is proposed for L. subplinthogalus var. chiangmaiensis.

Characterization and comparative analysis of six complete mitochondrial genomes from ectomycorrhizal fungi of the Lactarius genus and phylogenetic analysis of the Agaricomycetes

Lactarius is one of the most prominent genera of mushroom-forming fungi in the world. In the present study, complete mitochondrial genomes (mitogenomes) from six Lactarius species were sequenced and assembled. The six mitogenomes were all composed of circular DNA molecules, with total lengths ranging from 38,445 bp to 60,843 bp. The GC contents, GC skews, and AT skews of the mitogenomes varied among the six species. Mitogenomic synteny analysis revealed the presence of gene rearrangements among the mitogenomes. Among the 15 core protein coding genes (PCGs) within the mitogenomes, nad4L exhibited the least genetic distance among species, indicating a high degree of conservation. In addition, the Ka/Ks values for all 15 core PCGs were <1, suggesting that they were subject to purifying selection. Comparative analyses indicated that the increase of intron numbers and sizes contributed to the expansion of mitogenomes in Lactarius. Phylogenetic analyses based on three combined gene datasets yielded identical and well-supported (BPP ≥ 0.83) topologies, dividing the six Lactarius species into two groups. This study provides the first report of mitogenomes from Lactarius and promotes further understanding of the genetics, evolution, and phylogenetic relationships of this important ectomycorrhizal fungal genus.

First Report of Eight Milkcap Species Belonging to Lactarius and Lactifluus in Korea

Lactarius and Lactifluus are milkcaps that are characterized by the secretion of latex. These two genera are part of a globally distributed cosmopolitan group of ectomycorrhizal fungi that is an important food resource in various ecosystems. Recently, the taxonomy of Lactarius and Lactifluus has been revised based on molecular phylogenetics. Despite the importance of these taxa, Korean species of both genera are poorly understood. In an effort to describe milkcap species that are indigenous to Korea, a long-term study has been initiated. During a recent survey, eight species of milkcaps that were previously unrecorded in Korea were detected based on morphological observation and sequence analysis of the internal transcribed spacer region: five Lactarius species (Lactarius atromarginatus, L. austrotorminosus, L. kesiyae, L. tabidus, and L. vietus) and three Lactifluus species (Lactifluus acicularis, Lf. pilosus, and Lf. pinguis). Detailed morphological descriptions and phylogenetic relationships of these species are provided in this article.

Two Lactarius species mycorrhizal with Cistus laurifolius in Turkey

Two Lactarius species mycorrhizal with Cistus laurifolius in Turkey

New reports, phylogenetic analysis, and a key to Lactarius Pers. in the Greater Yellowstone Ecosystem informed by molecular data

The Greater Yellowstone Ecosystem (GYE), located in the Central Rocky Mountains of western North America, is one of the largest nearly intact temperate-zone ecosystems on Earth. Here, Lactarius is an important component of ectomycorrhizal communities in many habitat types, from low elevation riparian areas to high elevation conifer forests and alpine tundra. Molecular phylogenetic analyses of ITS and RPB2 gene sequences along with detailed morphological examination confirm at least 20 Lactarius species, as well as three varieties, and one unresolved species group in the GYE. Eight taxa are reported from the GYE for the first time, and nearly every major ectomycorrhizal host plant in the GYE appears to have at least one Lactarius species associated with it. Broad intercontinental distributions are suggested for alpine Salix and Betula associates, and for certain subalpine Picea and aspen (Populus spp.) associates. Some species appear to be restricted to western North America with Pinus, Pseudotsuga or Abies. The distribution and/or host affinities of others is not clear due in part to ambiguous host assignment, taxonomic problems or the relative rarity with which they have been reported.

Two new Lactarius species from a subtropical cloud forest in eastern Mexico

Two species of Lactarius from the subtropical montane cloud forest of central Veracruz are described as new. Both species are placed in subgenus Lactarius based on an accurate study of macro- and micromorphological features and supported by molecular phylogenetic analyses of a single nuc rDNA ITS1-5.8S-ITS2 (ITS), a concatenated ITS, D1, and D2 domains of nuc 28S rDNA (28S), and part of the second largest subunit of the RNA polymerase II (rpb2) (6–7 region) sequence datasets. In the phylogenetic reconstruction presented, the two species appear nested in two clearly distinct, well supported clades that reveal their phylogenetic position among members of subgenus Lactarius (= subg. Piperites s. auct.), a complex group of which a worldwide phylogeny requires further study. According to field observations, both taxa are possible ectomycorrhizal associates of Quercus spp. and one of Fagus grandifolia var. mexicana. Taxonomic descriptions based on the study of specimens gathered during fieldwork from 2012 to 2014 are presented. Descriptions are accompanied with illustrations of macro and micromorphological characters and a discussion of related species is provided.

Mercury accumulation of three Lactarius mushroom species

Accumulation, distribution and potential dietary intake of mercury accumulated by mushrooms of Lactarius species L. delicious, L. volemus and L. deterrimus were studied in the Pomerania region of Poland. In total, 212 fruiting bodies and 106 underlying topsoil samples were analyzed. Analysis indicated that the concentrations of Hg were at low levels both in mushrooms and forest topsoils for a majority of the locations investigated. L. volemus that grew in soils with only a slightly elevated contamination (0.11±0.07mgkg−1 of dried soil), very efficiently accumulated Hg in fruiting bodies and concentration levels were at 3.7±1.3mgkg−1 of dry biomass in caps and at 1.9±0.9mgkg−1 of dry biomass in stipes. Consumption of mushrooms foraged from the Sobowidz forest, which is close to a foundry using ferrous and non-ferrous metals could result in a Hg intake that exceeds the current statutory limits.

Lactarius megalopterus, a new angiocarpous species from a tropical rainforest in Central Africa, shows adaptations to endozoochorous spore dispersal

A new sequestrate Lactarius species was found in a humid evergreen tropical rainforest dominated by Fabaceae of the subfamily Caesalpinioideae in Cameroon, Central Africa. It is described here as new to science and is named Lactarius megalopterus, referring to its spore ornamentation of extraordinarily high wings. Anatomical characters and molecular systematic analyses confirm its relationship to Lactarius subgenus Plinthogali. Phylogenetic analyses based on two nuclear DNA regions revealed its close relationship to Lactarius angiocarpus, which is also an angiocarpous species from Zambia in Africa. Molecular studies have shown that tuber-like, sequestrate sporocarps evolved independently in several lineages of Basidiomycota. The findings of sequestrate fungi in tropical rainforests raise questions regarding the evolutionary benefit of enclosing the spore-producing hymenium. The enclosure of spore-producing tissue has often been associated with the protection of the delicate hymenium against desiccation in arid habitats or against frost in cold habitats. However, these cannot be the selective factors in warm and humid areas like the tropics. This controversy is exemplarily studied and discussed in the family of Russulaceae, especially in the genus Lactarius. Characters shown by the angiocarpous sporocarp of the new Lactarius, such as thick-walled statismospores, an aromatic smell and mild taste, can be interpreted as adaptations to endozoochorous spore dispersal by mammals. Therefore, here we prefer the alternative hypothesis that sequestrate sporocarps are the result of adaptation to endozoochorous spore dispersal.

Expanding current knowledge on the chemical composition and antioxidant activity of the genus Lactarius.

Despite the presence of toxic compounds in inedible mushrooms, the question whether the chemical nutrients and non-nutrients compositions in edible and inedible Lactarius species are similar remains unanswered. To answer this question, Lactarius citriolens Pouzar and Lactarius turpis (Weinm.) Fr., two inedible species, were studied in order to obtain information about their chemical composition and bioactivity. Free sugars, fatty acids, tocopherols, organic and phenolic acids were analysed by chromatographic techniques coupled to different detectors. L. citriolens and L. turpis methanolic extracts were tested regarding antioxidant potential (reducing power, radical scavenging activity and lipid peroxidation inhibition). The composition of macronutrients varied among the two species, but the profiles were similar between them and among other Lactarius species; L. citriolens gave the highest energy contribution, saturated fatty acids and organic acids, while the L. turpis sample was richer in free sugars, mono- and polyunsaturated fatty acids, tocopherols and phenolic compounds. L. turpis methanolic extract showed the highest antioxidant activity. The absence of hepatoxicity of the methanolic extracts was confirmed in porcine liver primary cells (in vitro conditions). The present study provided new information about wild L. citriolens and L. turpis, comparing their chemical composition and antioxidant properties with other Lactarius species, and expanding the knowledge about this genus.

Proximate Composition, Acute Toxicity and Antioxidative Property of Lactarius tenuicystidiatus , a New Species

The proximate composition, nutritional value and antioxidative activity of a new species Lactarius tenuicystidiatus and other three widely consumed Lactarius species (L. deterrimus, L. volemus sensu lato and L. hatsudake) from Southwest China were determined. The acute oral toxicity test of L. tenuicystidiatus was performed in mice. L. tenuicystidiatus mushroom presented higher protein (18.13 g/100 g dry weight [DW]) and crude fiber (12.26 g/100 g DW) contents, but lower ash level than the other three Lactarius species. Oleic acid (21.8 mg/g DW) and linoleic acid (17.7 mg/g DW) were major fatty acid components in L. tenuicystidiatus. Glutamine (4.88 mg/g DW) was the most abundant amino acid followed by glutamic acid, arginine and threonine in L. tenuicystidiatus. Some unusual nonprotein amino acids, γ-amino-n-butyric acid, L-α-amino-n-butyric acid and ornithine were also found. In the case of reducing power, 2,2-diphenyl-1-picrylhydrazyl and metal chelating activity, L. tenuicystidiatus possessed more antioxidant than other three Lactarius species. Moreover, acute oral toxicity study demonstrated that L. tenuicystidiatus was safe after oral administration to both male and female mice. Thus, the combination of rich nutritional composition and bioactivity in the new wild mushroom make it appropriate for functional food and nutritional supplements. Practical Applications Lactarius tenuicystidiatus is a new species from Southwest China that may be edible, delicious and popular in a limited area. It is therefore necessary to examine nutritional value, biology activity and the toxicity of the new mushroom. This study clearly demonstrates the proximate composition, amino acid and fatty acid profiles, and antioxidative activity of L. tenuicystidiatus. For the purpose of comparison, other three widely consumed Lactarius species are also analyzed to evaluate the nutritional value of L. tenuicystidiatus. It is suggested that the extract of the mushroom species evaluated here could be of use as an easily accessible source of natural antioxidant for the nourishment. The acute oral toxicity study demonstrated that L. tenuicystidiatus was safe after oral administration to both male and female mice. Thus, the new wild mushroom can be used as an ideal resource for a natural health food because of its abundant nutritive components and antioxidant activity.

A new angiocarpous Lactarius species from Thailand

Lactarius bisporus sp. nov. is described from primary tropical forest in Thailand. Morphological characters and DNA sequence data are given. Comparisons with the closely related angiocarpous taxon Lactarius pomiolens are provided.