ABSTRACT
The aim of this study was to evaluate four strains of Trichoderma spp. (T. harzianum IBLF 006 WP, T. harzianum IBLF 006 SC, T. harzianum ESALQ 1306 and T. asperellum URM 5911) for seedling growth promotion in laboratory and head lettuce yield in field conditions. The experiment was carried out in a completely randomized design with four treatments (strains): IBLF 006 WP, IBLF 006 SC, ESALQ 1306 and URM 5911 and a non-inoculated (without Trichoderma) control. Each treatment consisted of 200 seeds, arranged in four replicates. Lettuce seeds cv. Astra were treated with 2 mL Trichoderma suspension (2.5 x 108 conidia mL-1 per each 100 g seeds) and submitted to growth assay in laboratory up to 7 days after sowing. For field experiment, we opened furrows, which were manually sprayed with 5 x 107 conidia mL-1. Afterwards, seedlings were transplanted (4 to 6 leaves of head lettuce cv. Mauren) and harvested 40 days later. Each treatment consisted of four replicates (1.2 x 1.2 m, 16 plants per plot) arranged in randomized blocks. In both experiments, a control without Trichoderma application was included, and we evaluated shoot length, root and total length, shoot, root and total fresh mass and shoot, root and total dry mass, shoot mass ratio, root mass ratio and shoot/root ratio. The germination (%) was evaluated by laboratory tests, whereas in field experiment, height, stem diameter, head diameter, number of leaves and yield were evaluated. The T. harzianum strain ESALQ 1306 provided the best head lettuce growth rate in laboratory test, which was confirmed in field experiment, in which the productivity (50.2 t ha-1) was superior when compared to the other strains (41.38 to 44.23 t ha-1) and the control (30.18 t ha-1).
Keywords:
Trichoderma harzianum; Trichoderma asperellum; Lactuca sativa; biological control; horticulture