Comparative effects of two indole-producing trichoderma strains and two exogenous phytohormones on the growth of zea mays l., with or without tryptophan

Abstract

This research evaluated the growth responses of maize plants due to the inoculation of two indole-producing Trichoderma strains in comparison to the application of two exogenous phytohormones. Either T. tomentosum (EMMFRS1C2) or T. harzianum (MichV6S3C2) were inoculated as conidia or as fungal filtrates obtained from Luria-Bertani, liquid medium, with or without the addition of L-Tryptophan (1 g L-1). In addition, two concentrations (5 and 10 mg L-1) of indole acetic acid (IAA) and indole butyric acid (IBA) from which 2 mL were applied per plant. Twelve treatments and six replicates distributed in a completely randomized design. Plants were maintained for 50 days in microcosms (perlite and vermiculite, 2:1 v/v), under greenhouse conditions (38ºC±5) and watered every 48 h. The best plant growth responses (height, root length, leaf area, and root, stem and total dry weight were achieved by inoculating conidia of either T. tomentosum (EMMFRS1C2) or T. harzianum (MichV6S3C2) in combination with tryptophan (1 g L-1) when compared to control plants; but T. harzianum (MichV6S3C2) only resulted in beneficial effects in root length. Moreover, the application of fungal filtrates had similar plant growth responses than the application of either IAA or IBA at 5 mg L-1.