Variation among matsutake ectomycorrhizae in four clones of Pinus sylvestris

Pinus massoniana somatic embryo maturation, mycorrhization of regenerated plantlets and its resistance to Bursaphelenchus xylophilus

Pine wilt disease, caused by the pine wood nematode (PWN, Bursaphelenchus xylophilus), is a major quarantine forest disease that poses a threat to various pine species, including Pinus massoniana (masson pine), worldwide. Breeding of PWN-resistant pine trees is an important approach to prevent the disease. To expedite the production of PWN-resistant P. massoniana accessions, we investigated the effects of maturation medium treatments on somatic embryo development, germination, survival, and rooting. Furthermore, we evaluated the mycorrhization and nematode resistance of regenerated plantlets. Abscisic acid was identified as the main factor affecting maturation, germination, and rooting of somatic embryos in P. massoniana, resulting in a maximum of 34.9 ± 9.4 somatic embryos per ml, 87.3 ± 9.1% germination rate, and 55.2 ± 29.3% rooting rate. Polyethylene glycol was identified as the main factor affecting the survival rate of somatic embryo plantlets, with a survival rate of up to 59.6 ± 6.8%, followed by abscisic acid. Ectomycorrhizal fungi inoculation with Pisolithus orientalis enhanced the shoot height of plantlets regenerated from embryogenic cell line (ECL) 20-1-7. Ectomycorrhizal fungi inoculation also improved the survival rate of plantlets during the acclimatization stage, with 85% of mycorrhized plantlets surviving four months after acclimatization in the greenhouse, compared with 37% non-mycorrhized plantlets. Following PWN inoculation, the wilting rate and the number of nematodes recovered from ECL 20-1-7 were lower than those recovered from ECL 20-1-4 and 20-1-16. The wilting ratios of mycorrhizal plantlets from all cell lines were significantly lower than those of non-mycorrhizal regenerated plantlets. This plantlet regeneration system and mycorrhization method could be used in the large-scale production of nematode-resistance plantlets and to study the interaction between nematode, pines, and mycorrhizal fungi.

Ectomycorrhization of Tricholoma matsutake with Quercus aquifolioides affects the endophytic microbial community of host plant

Tricholoma matsutake (S. Ito et Imai) is an ectomycorrhizal basidiomycete associated with Pinaceae and Fagaceae trees in the Northern Hemisphere. It is still unknown whether the symbiotic relationship with this ectomycorrhiza could affect the host plant's endophytic microbial community. In this study, we used high throughput sequencing to analyze the endophytic microbial communities of different Quercus aquifolioides tissues with or without T. matsutake partner. About 35,000 clean reads were obtained per sample, representing 34 bacterial phyla and 7 fungal phyla. We observed 3980 operational taxonomic units (OTUs) of bacteria and 457 OTUs of fungi at a 97% similarity level. Three bacterial phyla, Proteobacteria, Cyanobacteria, and Bacteroidetes, and the fungal phylum Ascomycota were dominant in all tissues. The relative abundance of these taxa differed significantly between Q. aquifolioides tissues with and without T. matsutake partner (p < 0.05). The bacterial genus Pseudomonas and the fungal genus Cryptosporiopsis were more abundant in mycorrhized roots than in control roots. This study showed that the community structure and dominant species of endophytic microbial communities in Q. aquifolioides tissues might be altered by colonization with T. matsutake. This work provides a new insight into the interactions between ectomycorrhizal fungus and host plant.