Estudo da germinação e do efeito de Trichoderma spp. no crescimento de Gochnatia polymorpha (LESS.) Cabrera

Abstract

The production and cultivation of native tree seedlings have difficulties that can be attended to through the knowledge of the environmental factors and microorganisms affecting seed germination, as well as the interaction between forest species and the Trichoderma, which is a genus of fungi used in plant pathogens biological control and promotion of plant growth. This study aimed to investigate the germination of Gochnatia polymorpha (Less.)Cabrera, identifying the fungi associated with diaspores and evaluate the effect of Trichoderma spp. in promoting germination and plant growth. In the study of seed germination, the seeds have been subjected to temperatures of 15°, 20°, 25° and 30° C with a photoperiod of 16 hours and continuous darkness. In another experiment the effect of sodium hypochlorite (NaClO) has been evaluated on seed germination and contamination of the seeds with and without Papus at concentrations of 0, 1, 2, 3 and 4%. Identification of fungi present in the diaspores has been performed by the methods of filter paper and plating on BDA culture medium. In the study of the interaction between G. polymorpha and Trichoderma spp. TSM1 and TSM2 isolates of Trichoderma viride, 2B2 and 2B22 of Trichoderma harzianum and two commercial products, Agrotrich® and Trichodermil®, have been analyzed in the contamination of and germination of the seeds, using the cellophane in vitro technique .The antagonism of these isolates to four fungi of the genera Bipolaris, Alternaria, Cladosporium and Phoma, previously isolated from diaspores, has been evaluated by the technique of direct confrontation. The ex vitro interaction experiments have been conducted in a greenhouse with autoclaved and not autoclaved substrates. It has been concluded that the seeds germinated both in the presence and absence of light and temperatures of 15° and 20° C have been the most appropriate. The tested concentrations of NaClO did not interfere with seed germination, but in diaspores with papus the lowest contamination rates have been in the concentrations of 0% and 4%; yet in the diaspores without papus, the lowest rates have been in the concentrations of 3, 4 and 0%. In the diaspores the fungi genera Bipolaris, Alternaria, Cladosporium, Phoma, Aspergillus and Epicoccum have been identified. By the technique of in vitro cellophane, all tested isolates of Trichoderma spp. have been effective in controlling the contamination of the seeds, but it has been not possible to assess the effect of Trichoderma spp. in seed germination. In direct confrontation technique, the 2B22 isolate and the product Agrotrich ® have been the most effective. In both autoclaved and not autoclaved substrates, the tested isolates did not interfere in seedling emergence, but the isolates of 2B2 and 2B22 of T. harzianum promoted the vegetative growth of G. polymorpha.