Potencial de Trichoderma spp. no biocontrole da fusariose e na promoção de crescimento de mudas em pimenteira-do reino na Amazônia Oriental.

Abstract

Fungi of the genus Trichoderma spp. are known to establish beneficial interactions with plants. For the efficient management of black pepper (Piper nigrum L.) in the Amazon region, ecological methods promoting the biological control of fungal diseases in the crop and plant growth can be considered viable options given the unexplored biodiversity existing in the Amazon. The objectives of the study include: (i) obtaining Trichoderma spp. isolates from areas with Piper spp. in the Eastern Amazon, (ii) selecting isolates antagonistic to F. solani f. sp. piperis through in vitro tests, (iii) evaluating the capacity of Trichoderma spp. isolates to produce lytic enzymes, (iv) determining the potential of Trichoderma spp. isolates to reduce the severity of black pepper fusariosis, (v) determining the capacity of Trichoderma spp. isolates to produce plant growth hormone, and (vi) investigating the ability of Trichoderma spp. isolates to promote growth in black pepper seedlings and evaluate their effects on plant biochemical responses. Collections to obtain Trichoderma spp. isolates were carried out in four municipalities of the Eastern Amazon in areas cultivated with Piper spp. A total of 80 Trichoderma spp. isolates were obtained and evaluated in in vitro tests for antagonistic action against Fusarium solani f. sp. piperis, the causal agent of black pepper fusariosis, and for their capacity to produce lytic enzymes. Eight antagonistic isolates (T9, T18, T44, T62, T69, T76, T77, and T80) were selected in in vitro tests and evaluated for their biocontrol potential against fusariosis in black pepper seedlings. Trichoderma spp. isolates were also tested for their capacity to produce indole-3-acetic acid (IAA). The isolates that showed the best results (T03, T05, T07, T08, T13, T15, T21, T42, T45, T56, T63) were tested for their effects on black pepper seedling growth. Leaf and root biochemical analyses were conducted to evaluate the effects of Trichoderma spp. inoculation on seedling biochemical responses. Regarding biocontrol tests, most Trichoderma spp. isolates efficiently inhibited the mycelial growth of F. solani f. sp. piperis and produced at least one lytic enzyme. In the in vivo assay, all selected Trichoderma spp. isolates showed significant antifungal activity, ranging from 27.30% to 77.80% reduction in fusariosis symptom severity compared to the control. Isolates T18 and T80 were selected as promising biocontrol agents against black pepper fusariosis. In the growth promotion assay, some Trichoderma spp. isolates promoted black pepper seedling growth compared to the control treatment, 60 days after transplantation. Isolate T21 was the most efficient in growth responses, suggesting it could be a potential growth promoter for black pepper seedlings. Significant biochemical responses in black pepper seedlings related to nitrogen metabolism indicate a good metabolic regulatory state of the plant in the presence of Trichoderma spp. The evidence provided in this study strongly supports the possibility of using Trichoderma spp. as a safe, environmentally friendly, and effective biocontrol agent and growth promoter for black pepper cultivation.