Mycorrhizal Fungal Partners Remain Constant during a Root Lifecycle of Pleione bulbocodioides (Orchidaceae).

Jiao Qin,Shi-Bao Zhang,Wei Zhang,Jing-Qiu Feng

doi:10.3390/jof7110994

Abstract

Mycorrhizal mutualisms are vital for orchids through germination to adulthood. Fungal species diversity and community composition vary across seasons and plant development stages and affect plant survival, adaptation, and community maintenance. Knowledge of the temporal turnover of mycorrhizal fungi (OMF) remains poorly understood in the eco-physiologically diverse orchids (especially in epiphytic orchids), although it is important to understand the function and adaptation of mycorrhizae. Some species of Pleione are epiphytic plants with annual roots and may recruit different fungal partners during their root lifecycle. Based on continuous samplings of Pleione bulbocodioides during a whole root lifecycle, we characterized the fungal temporal dynamics using Illumina sequencing of the ITS2 region. Our data showed that the plants of P. bulbocodioides were quickly colonized by OMF at root emergence and had a constant OMF composition throughout one root lifecycle, although the OMF richness declined with root aging after a peak occurrence during root elongation. In contrast, the richness of root-inhabiting fungal endophytes kept increasing with root aging and more drastic turnovers were found in their species compositions. Our findings of OMF temporal turnover contribute to further understanding of mycorrhizal associations and adaptation of Orchidaceae and will benefit orchid resource conservation and utilization.

Highlights

Fungal associates provide plants with a range of benefits and play crucial roles in plant survival and diversifications [1]
Sebacinoid, tulasnelloid, and ceratobasidioid fungi were predominant in roots of P. bulbocodioides, with a large portion of orchid mycorrhizal fungi (OMF) Operational taxonomic unit (OTU) that were root age-independent and six of the later three families had colonized 90% of the individual plants (Figure 5, Table S1)
We found that a persistent core of OMF exists throughout one root lifecycle of a lithophytic orchid, P. bulbocodioides

Summary

Introduction

Fungal associates provide plants with a range of benefits and play crucial roles in plant survival and diversifications [1]. Common temporal changes within symbioses, ranging from lifelong fidelity to total replacement of fungal partners, exist because plant physiological demands and ecological factors can change over time. Temporal turnovers of mycorrhizal fungi associated with different plants have drawn wide attention because of the importance in understanding functions and adaptations of mycorrhizae [3,4]. Fungal interactions are critical for orchids because their dust-like seeds that contain only minimal nutrient reserves, cannot develop to the seedling stage without the establishment of an association with orchid mycorrhizal fungi (OMF) [9]. Seed germination and protocorm development of orchids require organic carbon provided by fungal

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