Densidade populacional de Fusarium sp. submetido a variações de fatores físicos, aplicação de Trichoderma harzianum e germinação conidial

Abstract

Fusarium is a widely distributed fungus, highly resilient and adaptable, responsible for severe diseases in various agricultural crops. Its ability to survive and adapt to climate change reinforces its global economic and phytopathological relevance. In this study, the aim was to estimate the population density of Fusarium sp. under different physical conditions, evaluate the effect of Trichoderma harzianum application, and characterize conidial germination. Soil samples were collected in gerboxes at the State University of Goiás, South Campus, Ipameri Unit. The gerboxes were divided into two treatments: control, intended for quantification of the natural population density of Fusarium sp., and biological treatment, which previously received a suspension of T. harzianum. The treatments were subjected to temperatures of 16, 20, 24, 28, and 32°C for ten days of incubation in BOD chambers under a 12 h photoperiod. After the incubation period, 1 g of soil was removed from the gerbox and suspended at a 1:100 dilution. Aliquots of 1 mL of this suspension were transferred to Komada medium for seven days at 24°C under a 12 h photoperiod. Subsequently, the number of colonies formed was counted, and the estimate expressed per gram of soil. In parallel, isolate Q-01-08 was obtained and subjected to pathogenicity tests on bean seeds, as well as evaluation of initial germination time, germ tube growth, and microconidia germination percentage. The experiment was conducted in a completely randomized design. The highest Fusarium density occurred around 24–25°C, reduced by approximately 55% at extreme temperatures and by 30–60% due to the action of T.harzianum. Isolate Q-01-08 showed high pathogenicity in bean seeds. Molecular identification based on ITS sequencing revealed 567/569 bp similarity with F. solani sequences. Temperature and light regime influenced germination, with delays at lower ranges, limitation between 24–27°C under light, and promotion of growth at 28–32°C in darkness, which also increased germination percentage above 24°C. It is concluded that the isolate has economic importance due to its pathogenicity and that its growth and behavior are strongly modulated by light and temperature conditions.