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Lactarius indigo
Lactarius indigo (actual genome source) by Brian P. Looney

This genome was sequenced as part of the JGI CSP “1KFG - Deep Sequencing of Ecologically-relevant Dikarya“ and more specifically as a part of the Russulaceae Sequencing Project, which seeks to densely sample members of a diverse lineage of ectomycorrhizal (ECM) fungi to examine functional diversity of ECM fungi with a shared evolutionary history.

Lactarius indigo (Schwein.) Fr. – The Indigo Milk Cap

Lactarius indigo is a distinctive species of Lactarius sect. Deliciosi found throughout eastern North American and Central America (Nuytinck et al. 2006). It is characterized by having a blue, zonate cap, strongly inrolled margin, blue gills, producing copious blue latex that is slightly acrid tasting, and a short blue stem (Hesler & Smith 1979). A variety of this species, Lactarius indigo var. diminutivus Hesler & A.H. Sm. is similar but has a smaller cap diameter (Hesler & Smith 1979). Lactarius indigo naturally forms ectomycorrhizal symbioses with hardwood and coniferous hosts and has been successfully synthesized with Eurasian and neotropical pines (Díaz et al. 2007). Lactarius indigo is considered a prime edible mushroom in Mexico and Central America by both local and indigenous groups (Robles-García et al. 2018). Like many species of Russulaceae, novel sesquiterpenoid compounds have been identified from L. indigo, including the azulene compound that give the mushroom its characteristic blue color (Harmon et al. 1980). This azulene compound has been used as the basis for developing fluorescent dyes to detect reactive oxygen species in cells (Murfin et al. 2019). The sporocarps for this genome were collected on October 1, 2018 in a mixed forest with mainly Pinus taeda and various species of Quercus in West Point on the Eno Park, Durham, NC. This species is a representative of a well-studied section of Lactarius that includes many popular edible mushrooms worldwide and will be important for understanding the evolution of functional diversity of Russulaceae.

Researchers who wish to publish analyses using data from unpublished CSP genomes are respectfully required to contact the PI and JGI to avoid potential conflicts on data use and coordinate other publications with the CSP master paper(s).


Díaz, G., Flores, R. and Honrubia, M., 2007. Lactarius indigo and L. deliciosus form mycorrhizae with Eurasian or Neotropical Pinus species. Nine, 32, p.45.

Harmon, A.D., Weisgraber, K.H. and Weiss, U., 1980. Preformed azulene pigments of Lactarius indigo (Schw.) Fries (Russulaceae, Basidiomycetes). Experientia, 36(1), pp.54-56.

Hesler, L.R. and Smith, A.H., 1979. North American species of Lactarius. University of Michigan Press. Ann Arbor.

Murfin, L.C., Weber, M., Park, S.J., Kim, W.T., Lopez-Alled, C.M., McMullin, C.L., Pradaux-Caggiano, F., Lyall, C.L., Kociok-Köhn, G., Wenk, J. and Bull, S.D., 2019. Azulene-Derived Fluorescent Probe for Bioimaging: Detection of Reactive Oxygen and Nitrogen Species by Two-Photon Microscopy. Journal of the American Chemical Society, 141(49), pp.19389-19396.

Nuytinck, J., Miller, S.L. and Verbeken, A., 2006. A taxonomical treatment of the North and Central American species in Lactarius sect. Deliciosi. Mycotaxon, 96, pp.261-308.

Robles-García, D., Suzán-Azpiri, H., Montoya-Esquivel, A., García-Jiménez, J., Esquivel-Naranjo, E.U., Yahia, E. and Landeros-Jaime, F., 2018. Ethnomycological knowledge in three communities in Amealco, Quéretaro, México. Journal of Ethnobiology and Ethnomedicine, 14(1), p.7.