Improved ex vitro survival of asymbiotically raised seedlings of Cymbidium using mycorrhizal fungi isolated from distant orchid taxa

• Two fungal endophytes isolated from the roots of epiphytic orchids Rhynchostylis retusa and Aerides multiflorum showed resemblance to Rhizoctonia-like fungi.
• The isolates were identified on the basis of their cultural characteristics, nuclei number and ITS region sequences.
• The fungal isolates formed mycorrhizal association and promoted growth in asymbiotically raised Cymbidium aloifolium and C. giganteum seedlings.
• The study showed the greater survival and growth increment in the inoculated seedlings of C. aloifolium tested on mass scale.

Two fungal endophytes isolated from the roots of epiphytic orchids Rhynchostylis retusa and Aerides multiflorum were employed for biological hardening of asymbiotically raised seedlings of Cymbidium aloifolium and C. giganteum. These fungal isolates showed resemblance to Rhizoctonia-like fungi in their cultural characteristics, microscopic features and ITS region sequences. The ITS region sequences of Ceratobasidium sp. strain RR showed 100% identity with Rhizoctonia sp. M2ao1 and Ceratobasidium sp. FPUB 168, whereas Ceratobasidium sp. strain AM displayed 89% identity with Ceratobasidium sp. JTO 031. The fungal isolates promoted growth and survival of seedlings of both species of Cymbidium, with greater promotory effects of Ceratobasidium sp. strain RR. The higher survival and growth increment in inoculated seedlings of C. aloifolium emphasized the importance of biological hardening of asymbiotically grown orchid seedlings.