Abstract
Abstract Fungi of Rhizoctonia complex are mycorrhizal of orchids and may to germinate yours seeds and development the seedlings. In this context, our objective was to select a fungal isolate to promote seed germination and seedling development of Cyrtopodium saintlegerianum. Pelotons were found in the roots and three mycorrhizal fungi were isolated. We tested mycorrhizal isolates obtained from C. saintlegerianum roots and six mycorrhizal fungi from other orchids as well three pathogenic isolates (of rice and bean) to germinate the seeds in oatmeal-agar medium. Seeds not inoculated were used as control. The isolates En07 (Waitea circinata), Cs10 (Tulasnella sp.) and Ro88 (Rhizoctonia oryzae) were efficient to promote seed germination, but only En07 differing statistically of the control. The non-specific isolate En07 promoted germination in 81% of seeds and the specific isolate (Cs10) promoted 60%, evidencing the non-specificity mycorrhizal association in this orchid during germination. Axenic seedlings were inoculated with four mycorrhizal fungi (non-inoculated seedlings - control). After six months, the isolates En07 and Cs10 were efficient in the interaction with the seedlings, but did not differ to the control. Therefore, our results suggested that fungi of the Rhizoctonia complex can be used in the germination and seedling development of C. saintlegerianum.
Highlights
Mycorrhizal associations are essential to the life cycle of orchids in natural habitat
The biological material was transported to the Laboratório de Genética de Microrganismos (LGM) at the Universidade Federal de Goiás (UFG) Brazil
Mycorrhizae microscopy characterization, fungal isolation and identification Root fragments of C. saintlegerianum were sectioned by freehand for optical microscopy (OM) observation
Summary
Mycorrhizal associations are essential to the life cycle of orchids in natural habitat. The interaction begins during seed germination when the mycorrhizal fungi infect basal cells in embryo. The hyphal coils formed into these cells are digested by the orchid to obtain carbon and nutrients necessary for its developmental initial phase. The seed produces a heterotrophic structure called the protocorm, which forms the seedling. The seedling produces its first root and fungi can colonize its cortical cells. From this phase, symbiosis with mycorrhizal fungi facilitates the acquisition of nutrients from the substrate (Peterson et al 2004; Rasmussen & Rasmussen 2009; Dearnaley et al 2012)
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