Fungalpedia – Note 51 Lactarius
Citation if using this entry: Bera et al. (2023) Basidiomycota. Mycosphere (in prep)
Described first time in Europe by Christian Hendrik Persoon (1797), Lactarius (Russulaceae, Russulales) is one of the most dominant ectomycorrhizal mushrooms in the subtropical to subtemperate forests playing a very significant ecological role in the terrestrial ecosystem. ‘Lac’ in Lactarius signify ‘milk’ in the Italian language, hence the genera’s naming due to the exudation of “milk” or latex when injured or bruised (Persoon 1797). Commonly, they are collectively called “milk caps”. The latex in Lactarius is contained in microscopic lactiferous hyphae which ramify and emerges to the hymenium without any septum forming pseudocystidia (Hesler & Smith 1979, Heilmann-Clausen et al. 1998). The genus has typical fleshy basidiomata with funnel to convex-shaped pileus attaching a well-defined stipe below without any kind of ring or volva (Hesler & Smith 1979, Heilmann-Clausen et al. 1998). The basidiomata can show a wide variation in colour, and surface characters. The macromorphological character like the colour change of the latex and the context on exposure or bruising is of great taxonomic significance (Hesler & Smith 1979, Heilmann-Clausen et al. 1998, Verbeken & Nuytinck 2013). The presence of conspicuous sphaerocytes makes their fruit bodies quite brittle which is a character for all genera belonging to the order Russulales (Hesler & Smith 1979, Heilmann-Clausen et al. 1998). However, the most striking character is the amyloid reaction of the basidiospore ornamentations with reagents like Melzer’s or Lugol’s (Hesler & Smith 1979, Heilmann-Clausen et al. 1998). Basidiospore shapes can also range from globose to elliptical having a diversified ornamentation pattern varying from isolated warts or spinoid to partial to completely reticulate or can be evidently winged (Le et al. 2007a, b, c, Verbeken & Nuytinck 2013). The hymenial and dermatocystidia are thin-walled with various types of apices and contents (Le et al. 2007a, b, c, Verbeken & Nuytinck 2013). The nature of the pileipellis and stipitipellis can be of various hyphal arrangements or only composed of pseudoparenchymatous cells or combination of both (Le et al. 2007a, b, c, Verbeken & Nuytinck 2013). Clamp connection is completely absent (Heilmann-Clausen et al. 1998).
The genus Lactarius has 450 species that have been discovered worldwide (Wijayawardene et al. 2022). All these species are classified into three subgenera: L. subg. Lactarius (Fr. ex J. Kickx f.) Kauffman, L. subg. Russularia (Fr.) Kauffman and L. subg. Plinthogalus (Berk.) Hesler & A.H. Sm. (Buyck et al. 2010).
Type species: Lactarius torminosus (Schaeff.) Gray
Fig 1. Lactarius torminosus (holotype) a. Basidiomata. b. Basidiospores. c. Cheilocystidia. d. Pleurocystidia. e. Pileipellis. Drawn from Heilmann-Clausen et al. 1998.
Buyck B, Hofstetter V, Verbeken A, Walleyn R 2010 – Proposals to conserve or reject names. 1919 Proposal to conserve Lactarius nom. cons. Basidiomycota with a conserved type. Taxon, 59(1), 295–296. https://www.cabdirect.org/cabdirect/abstract/20198647876
Heilmann-Clausen J, Verbeken A, Vesterholt J 1998 – The genus Lactarius. The Danish Mycological Society, Odense. 287 pp. https://biblio.ugent.be/publication/278976
Hesler LR, Smith AH 1979 – North American species of Lactarius. University of Michigan Press. USA. 841 pp. https://quod.lib.umich.edu/f/fung1tc/AAC3719.0001.001?view=toc
Le HT, Nuytinck J, Verbeken A, Lumyong S, Desjardin DE 2007a – Lactarius in Northern Thailand: 1. Lactarius subgenus Piperites. Fungal Diversity, 24(1), 173–224. https://www.fungaldiversity.org/fdp/sfdp/24-8.pdf
Le HT, Stubbe D, Verbeken A, Nuytinck J, Lumyong S, Desjardin DE 2007b – Lactarius in Northern Thailand: 2. Lactarius subgenus Plinthogali. Fungal Diversity, 27(1), 61–94. https://www.fungaldiversity.org/fdp/sfdp/27_5.pdf
Le HT, Verbeken A, Nuytinck J, Lumyong S, Desjardin DE 2007c – Lactarius in Northern Thailand: 3. Lactarius subgenus Lactariopsis. Mycotaxon, 102, 281–291. http://cmuir.cmu.ac.th/handle/6653943832/60782
Persoon CH 1797 – Tentamen dispositionis methodicae fungorum in classes, ordines, genera et familias, cum supplement adjecto. Petrum Philippum Wolf, Leipzig. https://www.biodiversitylibrary.org/bibliography/42674
Verbeken A, Nuytinck J 2013 – Not every milkcap is a Lactarius. Scripta Botanica Belgica, 51, 162–168. https://fungi.fr/Html/VerbekenNuytinckLactarius.pdf
Wijayawardene NN, Hyde KD, Dai DQ, Sánchez-García M……..Thines M 2022 – Outline of Fungi and fungus-like taxa-2021. Mycosphere, 13(1), 53–453. https://www.mycosphere.org/pdf/MYCOSPHERE_13_1_2.pdf
Ishika Bera, Center of Excellence in Fungal Research, Mae Fah Luang University, Chiang Rai 57100, Thailand
(Edited by Kevin D Hyde)