Root endophyte interaction between ectomycorrhizal basidiomycete Tricholoma matsutake and arbuscular mycorrhizal tree Cedrela odorata, allowing in vitro synthesis of rhizospheric “shiro”

Abstract

The ectomycorrhizal basidiomycete Tricholoma matsutake associates with members of the Pinaceae such as Pinus densiflora (red pine), forming a rhizospheric colony or "shiro," which produces the prized "matsutake" mushroom. We investigated whether the host specificity of T. matsutake to conifers is innately determined using somatic plants of Cedrela odorata, a tropical broad-leaved tree (Meliaceae) that naturally harbors arbuscular mycorrhizal fungi. We found that T. matsutake could form in vitro shiro with C. odorata 140 days after inoculation, as with P. densiflora. The shiro was typically aromatic like that of P. densiflora. However, this was a root endophytic interaction unlike the mycorrhizal association with P. densiflora. Infected plants had epidermal tissues and thick exodermal tissues outside the inner cortex. The mycelial sheath surrounded the outside of the epidermis, and the hyphae penetrated into intra- and intercellular spaces, often forming hyphal bundles or a pseudoparenchymatous organization. However, the hyphae grew only in the direction of vascular bundles and did not form Hartig nets. Tricholoma fulvocastaneum or "false matsutake" naturally associates with Fagaceae and was also able to associate with C. odorata as a root endophyte. With T. matsutake, C. odorata generated a number of roots and showed greatly enhanced vigor, while with T. fulvocastaneum, it generated a smaller number of roots and showed somewhat lesser vigor. We argue that the host-plant specificity of ectomycorrhizal matsutake is not innately determined, and that somatic arbuscular mycorrhizal plants have a great potential to form mutualistic relationships with ectomycorrhizal fungi.

Respuesta de plántulas de Cedrela odorata a la inoculación con Rhizophagus intraradices y diferentes niveles de defoliación

“…Tampoco se ha estudiado si la simbiosis puede ayudar en la respuesta o resistencia de esta especie al ataque de insectos como el barrenador de las meliáceas (Shi et al, 2006;Murata et al, 2013). En la mayoría de las plantaciones se utiliza planta producida en vivero, pero con baja calidad, susceptible a enfermedades y plagas.…”

“…Neither has been studied, whether symbiosis can help in the response or resistance of this species to insect attacks like the borer from Meliaceae (Shi et al, 2006;Murata et al, 2013). Most plantations use plants produced in nurseries, but with low quality, susceptible to diseases and pests.…”

Ectomycorrhizas in vitro between Tricholoma matsutake, a basidiomycete that associates with Pinaceae, and Betula platyphylla var. japonica, an early-successional birch species, in cool-temperate forests

“…matsutake Y1 (=ATCC MYA-915, NBRC 33136) has been described elsewhere (Murata et al 1999(Murata et al , 2013. Mycelia were grown at 25°C on modified Melin-Norkrans agar plates containing V8 juice (Murata et al 1999).…”

“…T. matsutake has been experimentally proven to associate with Picea abies, Pinus densiflora, and Pinus sylvestris as an ectomycorrhizal symbiont (Guerin-Laguette et al 2004, 2005Vaario et al 2010;Yamada et al 1999aYamada et al , b, 2006Yamada et al , 2010Yamada et al , 2013. Thin fungal hyphae penetrate the intercellular spaces of the root cortex, develop Hartig net structures and, in P. densiflora, establish a rhizospheric mycelial aggregate, or "shiro", that is required for fruiting in nature (Masui 1927;Yamada et al 1999aYamada et al , b, 2006.…”

“…Thin fungal hyphae penetrate the intercellular spaces of the root cortex, develop Hartig net structures and, in P. densiflora, establish a rhizospheric mycelial aggregate, or "shiro", that is required for fruiting in nature (Masui 1927;Yamada et al 1999aYamada et al , b, 2006. In vitro, shiros, which form in granite-based soil substrates, promote growth of P. densiflora and other species not regarded as hosts in nature (Murata et al 2013Yamada et al 2006;Yamanaka et al 2014). Recently, T. matsutake was proven to associate with Tsuga diversifolia (>1600 m a.s.l.)…”