Sibling spore isolates of Tricholoma matsutake vary significantly in their ectomycorrhizal colonization abilities on pine hosts in vitro and form multiple intimate associations in single ectomycorrhizal roots

Cultivation studies of edible ectomycorrhizal mushrooms: successful establishment of ectomycorrhizal associations in vitro and efficient production of fruiting bodies

Most edible ectomycorrhizal mushrooms are harvested in forests or controlled tree plantations; examples include truffles, chanterelles, porcinis, saffron milk caps, and matsutake. This study explored recent advances in in vitro ectomycorrhizal cultivation of chanterelles and matsutakes for successful ectomycorrhizal seedling establishment and the subsequent manipulation of these seedlings for efficient fruiting body production. Chanterelle cultivation studies have been limited due to the difficulty of establishing pure cultures. However, once pure cultures were established in the Japanese yellow chanterelle (Cantharellus anzutake), its ectomycorrhizal manipulation produced fruiting bodies under controlled laboratory conditions. As C. anzutake strains have fruited repeatedly under ectomycorrhizal symbiosis with pine and oak seedlings, mating tests for the cross breeding are ongoing issues. As one of the established strains C-23 has full-genome sequence, its application for various type of ectomycorrhizal studies is also expected. By contrast, Tricholoma matsutake fruiting bodies have not yet been produced under controlled conditions, despite successful establishment of ectomycorrhizal seedlings. At present, the shiro structure of ≈1L in volume can be provided in two y incubation with pine hosts under controlled environmental conditions. Therefore, further studies that provides larger shiro on the host root system are desired for the outplantation trial and fruiting.

Spore germination and ectomycorrhizae formation of Tricholoma matsutake on pine root systems with previously established ectomycorrhizae from a dikaryotic mycelial isolate of T. matsutake

In vitro ectomycorrhizal synthesis of Tricholoma matsutake with host plants has been widely conducted to elucidate fungal symbiotic properties for future cultivation practices. Here, we report on the importance of basidiospore inocula for this fungus to provide ectomycorrhizal seedlings in vitro. Ectomycorrhizal pine seedlings synthesized in vitro with cultured mycelium of T. matsutake (isolate #45 or #84) in a 250-mL culture vessel (soil volume) were transplanted to a large 1-L culture vessel. Fresh basidiospores of this fungus were aseptically inoculated on the ectomycorrhizal root system. The ectomycorrhizal seedlings in the 1-L vessel were grown for 9 months, and some plants were further grown for 6 more months under non-aseptic conditions in 4.1-L jars. The ectomycorrhizal seedlings previously inoculated with isolate #84 in the 1-L vessel showed significant ectomycorrhizal biomass (mycorrhizal root length) after spore inoculation. The ectomycorrhizal seedlings in the 4.1-L vessel showed large shiro structures (> 10 cm in diameter). PCR amplification of intergenic spacer 1 of the rRNA gene and long terminal repeat retroelement of T. matsutake in ectomycorrhizal root tips in both the 1-L vessels and 4.1-L jars revealed the presence of amplicons of the previously inoculated culture isolate of T. matsutake and the new genet(s) that established via germination of the inoculated basidiospores. This is the first report that inoculated basidiospores of T. matsutake germinated and colonized the host root to generate ectomycorrhizae in vitro.

Successes and challenges in the sustainable cultivation of edible mycorrhizal fungi – furthering the dream

The cultivation of edible mycorrhizal fungi (EMF) has made great progress since the first cultivation of Tuber melanosporum in 1977 but remains in its infancy. Five cultivation steps are required: (1) mycorrhizal synthesis, (2) mycorrhiza development and acclimation, (3) out-planting of mycorrhizal seedlings, (4) onset of fructification, and (5) performing tree orchards. We provide examples of successes and challenges associated with each step, including fruiting of the prestigious chanterelles in Japan recently. We highlight the challenges in establishing performing tree orchards. We report on the monitoring of two orchards established between Lactarius deliciosus (saffron milk cap) and pines in New Zealand. Saffron milk caps yields reached 0.4 and 1100 kg/ha under Pinus radiata and P. sylvestris 6 and 9 y after planting, respectively. Canopy closure began under P. radiata 7 y after planting, followed by a drastic reduction of yields, while P. sylvestris yields still hovered at 690 to 780 kg/ha after 11 y, without canopy closure. The establishment of full-scale field trials to predict yields is crucial to making the cultivation of EMF a reality in tomorrow's cropping landscape. Sustainable EMF cultivation utilizing trees in non-forested land could contribute to carbon storage, while providing revenue and other ecosystem services.