Trichoderma spp. on treatment of Handroanthus serratifolius seeds: effect on seedling germination and development

Fungi of the genus Trichoderma are important microorganisms used in biocontrol processes and the promotion of plant development. However, they remain poorly studied in the context of forestry programs, especially those related to native Amazonian species. Thus, it is the aim of this study to evaluate the effects of different Trichoderma isolates on the germination and development of Handroanthus serratifolius seedlings. During in vitro germination tests, seeds were immersed for 24 h in respective fungal suspensions each prepared using one of five Trichoderma isolates. The suspensions were held in plastic trays and kept at a temperature of 24 ± 2 °C. Metrics related to germination and development assessed under laboratory conditions include: germination speed index (GSI), germination percentage, length of the roots, and hypocotyls, as well as fungal perseverance. In the nursery, Trichoderma were used in two different applications: pre-planting treatment and as a monthly, post-planting treatment. Pre-planting treatments consisted of 10 g of colonized rice grains bearing each isolate being placed into experimental bags five days before seeding. The post-planting treatment involved the application of 10 mL of fungal suspension per experimental bag. Each month, the height, stem diameter, and leaf number were measured for each seedling. At the end of the experiment, the length and mass of roots as well as the total dry mass were recorded. In laboratory conditions, seeds treated with Trichoderma asperellum -TAM03 obtained the greatest fractional germination (76.5%) and GSI. In the nursery experiments, isolates TAM01 and TAM03, when applied as a post-planting treatment, increased the height, stem diameter, and number of leaves of treated plants with respect to the control group by 180 days post-treatment. After 365 days, plants which received TAM01 pre-planting treatments were observed to have increased root and aerial part length, as well as root mass and overall dry mass. These results suggest that T. asperellum -TAM01 positively affects H. serratifolius development.