Mycorrhizal Compatibility and Germination-Promoting Activity of Tulasnella Species in Two Species of Orchid (Cymbidium mannii and Epidendrum radicans)

Qianyu Yang,Lixiong Liang,Lubin Li,Lu Xu,Wei Xia,Lei Liu,Lijun Xu,Xiao Bai

doi:10.3390/horticulturae7110472

Abstract

In nature, Orchidaceae seeds establish a relationship with orchid mycorrhizal fungi to obtain essential nutrients for germination. The orchids, Cymbidium mannii and Epidendrum radicans, have significant ornamental and economic value. We isolated and cultured mycorrhizal fungi from C. mannii, E. radicans, and C. goeringii roots. Three strains of fungi, Tulasnella calospora (Tca), T. asymmetrica (Tas), and T. bifrons (Tbi), were identified using ITS-rDNA sequencing. Their mycorrhizal compatibility, germination-promoting effects, and symbiosis with the seeds of C. mannii and E. radicans were studied in vitro using various concentrations of oatmeal agar (OA) medium. Tca exhibited significant seed-germination-promoting effects on C. mannii (92.1%) and E. radicans (84.7%) on 2.0 and 4.0 g/L OA, respectively. For Tbi and Tas, the highest germination percentages were observed on 4.0 g/L OA in E. radicans (73.60% and 76.49%, respectively). Seed germination in C. mannii was enhanced by high oatmeal concentrations (8.0 and 12.0 g/L) during symbiosis with Tas, whereas Tbi had no effect regardless of OA concentration. Tca exhibited high compatibility with C. mannii and E. radicans, and the oatmeal concentration of the medium affected this compatibility. The findings of this study will aid in the propagation of endangered orchid species for conservation and commercial purposes using mycorrhizal technology.

Highlights

Orchidaceae is widely regarded as the largest and most diverse family of angiosperms, consisting of 17,000–35,000 species and encompassing 8% of all vascular plants [1,2]
Mycorrhizal fungi were isolated from three orchid plants (Table 1)
Strains Tulasnella calospora (Tca) and Tbi were clustered with T. calospora strain MAFF P305802 (DQ388042) and T. bifrons specimen voucher BPI 724,849 (AY373290), respectively

Summary

Introduction

Orchidaceae is widely regarded as the largest and most diverse family of angiosperms, consisting of 17,000–35,000 species and encompassing 8% of all vascular plants [1,2]. Germination and protocorm development depend on compatible mycorrhizal fungi to obtain carbon, water, and nutrients under natural conditions [5,6,7]. Given this obligate requirement, at least in the early developmental stages, obtaining optimal sources of mycorrhizal fungi and understanding the patterns of orchid–mycorrhizal relationships may facilitate the conservation of threatened orchid species and are, important steps for seed-based orchid conservation [8,9,10]. Compatibility between mycorrhizal fungi and orchids has an important effect on successful symbiotic seed germination [11].

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