Arbuscular mycorrhizal fungal communities in the roots of understory photosynthetic herbaceous plants

Mycoheterotrophic plants forming Paris-type arbuscular mycorrhiza (AM) exhibit two distinctive mycorrhizal features, digestion of fungal materials and specialization toward particular fungal lineages. To explore the possibility of partial mycoheterotrophy, i.e., both photosynthetic and mycoheterotrophic nutritional strategies, in AM plants, these features were investigated in 13 understory green herbaceous plant species collected from five Japanese temperate forests. Through microscopic observations, digestion-like hyphal structures were observed in four species, Disporum sessile and Disporum smilacinum in Colchicaceae, and Gentiana scabra and Swertia japonica in Gentianaceae. However, amplicon sequencing of AM fungal SSU rDNA using Illumina Novaseq 6000 revealed that all examined plant species exhibited less specificity toward AM fungi. Moreover, several AM fungi were consistently found in the majority of plant individuals across the study sites and plant species.