Prospecção de fungos micorrízicos e promoção de crescimento em orquídeas

Abstract

Orchid seeds do not have practically reserve of energy and are not able to absorb what exists, necessitating a symbiosis with mycorrhizal fungi for germination to occur. During the aclorophyll stage of embryo development, these are the dependent on the mycorrhizal association, because fungi provide simple sugars to the plant from digested pelotons. The objective of this work was to isolate mycorrhizal fungi of orchid in cultivated and wild plants, that could promote the germination and development of seedlings of different species. Roots of nine species of orchids were collected for the isolation by peloton, four of natural environment, three from in vitro culture that developed and grew in greenhouse orchid and two who were born spontaneously in the greenhouse orchid. This methodology promoted the isolation of nine anamorphic rhizoctonioid from two species from a natural environment, Prescotia sp and Oeceoclades maculata and of a spontaneous species in greenhouse orchid, Arundina bambusifolia. In pots of three species of orchids, Vanda sp., Cattleya tigrina and Cattleya walkeriana, were placed baiting containing seeds of the same. This methodology obtainedthe isolation of eight anamorphic rhizoctonioid fung from Cattleya tigrina and Cattleya walkeriana. Were made the quantitative and qualitative morphological characterizations of the 17 isolates obtained by the two methodologies, and these characteristics were used for the formation of groups by the grouping method UPGMA. This method together with the morphological characteristics made it possible to classify four genera of mycorrhiza, Epulorhiza, Ceratorhiza, Moniliopsis and Rhizoctonia-like. The isolates were separated into 7 different groups, and one isolate from each group was used for the symbiotic germination of six species of orchids, Cattleya brevicaulis, Cattleya tigrina, Cattleya walkeriana, Cattleya labiata, Dendrobium signatum and Encyclia cordigera. Posteriorly confirmation of the mycorrhizal association was made, of protocorm resulting from symbiotic germination. Ninety days after seeding, seedlings of the six species that germinated were transferred to flasks, and 180 days after seeding were evaluated growth and dry mass variables. The methodology of isolation by peloton promoted the isolation of mycorrhiza from plants of natural environment and from a spontaneous in greenhouse orchid, the baiting methodology was able to promote the isolation of mycorrhiza from plants that were born and developed in a controlled environment. Of the seven inoculum, six were efficient to promote the germination of the six species tested, but only five inoculum presented growth of seedlings. One inoculum is no specific, presenting better results, improving seedling growth in five of the evaluated species.