Seleção de isolados de Trichoderma spp. para o tratamento de sementes de tomate visando a proteção contra patógenos de solo e de armazenamento e promoção de crescimento

Abstract

Bioassays were conducted at Universidade Federal Rural do Rio de Janeiro, departamento de Fitotecnia to (i) determinate a simple and efficient preservation method of Trichoderma spp; (ii) evaluate the viability of essays in gerboxes with Trichoderma spp.; (iii) evaluate the potential of storaging seeds treated with Trichoderma isolates (iv) evaluate the survival of antagonistic fungi; (v) assess the level of protection of seeds against storage fungi and (vi) select Trichoderma isolates which improves velocity of emergence, development and nutrition of seedlins under greenhouse conditions. Fourty isolates, originated from rizosphere soil, roots, seeds, and stems of tomato cultivar Santa Clara Miss Brasil were used. The treatments were applied by immersion of seeds in water suspension containing Tween 80 (one drop.L- 1) for 10 minutes, adjusted to a concentration of 5x104 conidia.mL-1. As controls, original samples of tomato seeds without any treatment plus solution of water and Tween 80 plus Captan (3g.kg-1) were used. Further evaluations in laboratory conditions were performed by seed germination tests, and evaluation of seedlings development on two kinds of substrate, soil and a commercial substrate. To evaluate the survival of isolates with the time, seeds were treated and stored for 60 and 180 days, following the same procedures above. On the majority of tests performed under laboratory conditions, significant differences were observed among treatments on the velocity of germination and the percentage of seeds and seedlings colonized by Trichoderma, even after the storage for 180 days. Under greenhouse, independently of the substrate used, significant effect of various isolates on emergence and development of seedlings, expressed by height of stem, length of roots, weight of fresh and dry mass and contents of N and P were observed. On the essays in gerboxes and in the greenhouse, seeds, seedlings and roots were easily and rapidly colonized by the different isolates tested. Damage to seedlings was verified only in gerboxes , probably due to the existence of favourable conditions to the antagonistic fungi. The trials under laboratory conditions also revealed the possibility of using Trichoderma isolates as a protection agent of tomato seeds against storage fungi. From the 40 isolates evaluated, TENA1, TENA7, TENA16, TENA31 and TENA33 were selected as promising for treating.