Efficiency of mycorrhizal fungi for seed germination and protocorms development of commercial Cattleya species (Orchidaceae)

Orchidaceae is one of the largest plant families and stands out for its wide variety of flowers with ornamental and environmental importance. Cattleya is one of the main commercial genera, presenting a great diversity of species and hybrids that attract the attention of collectors, orchid enthusiasts, and consumers. In their natural environment, orchids associate with mycorrhizal fungi, which are responsible for providing carbon and other nutrients during seed germination. This study investigated the potential of mycorrhizal fungi isolated from the genus Cattleya for in vitro symbiotic germination of seeds from three contrasting Cattleya species, comparing them with non-symbiotic germination in a commercially used culture medium for orchid propagation. The isolated fungi were molecularly identified through phylogenetic analyses of DNA sequences using the ITS (Internal Transcribed Spacer) region. Three isolates obtained were identified as Tulasnella amonilioides, and through microscopic evaluations, the formation of monilioid cells was observed, a morphological characteristic previously unknown for this species. The T. amonilioides isolates were efficient in promoting seed germination of Cattleya bicolor, Cattleya walkeriana and Cattleya jongheana and accelerated the germination process when compared with the non-symbiotic commercial medium, showing to be promised for commercial seed production of these orchids species.