Chaetomium-like como potencial agente de controle biológico de Ceratocystis fimbriata

Abstract

Brazil has an area of 7.53 million hectares of planted Eucalyptus forests. Due to high productivity and extensive cultivation areas, there is a predisposition to the occurrence of diseases such as Ceratocystis wilt. Ceratocystis fimbriata is a soil-inhabiting fungus of significant forestry importance, known for its challenging control and substantial negative impact on wood and cellulose production. The Chaetomium-like genus has demonstrated effectiveness in plant pathogen control. Therefore, the objective of this study was to conduct in vitro tests with Chaetomium-like isolates to evaluate their potential in controlling C. fimbriata. The paired culture technique with three repetitions for each Chaetomium-like isolate against C. fimbriata was employed. Initial multiplication of Chaetomium-like isolates and the pathogen occurred in Petri dishes containing potato dextrose agar (PDA) and were maintained at 25 ± 1°C. Subsequently, mycelial discs from the pure cultures of both fungi were transferred to opposite sides, 1 cm apart, from the edge of new Petri dishes containing PDA. The pathogen was also cultured separately as a control. After 14 days, the most aggressive isolates (CT05B, CT07B, CT08A, CT13A, and CT13B) were selected based on the Bell Scale. Inhibition tests of spore germination were then conducted with the selected isolates. A spore suspension was prepared with 10 mL of sterilized distilled water, transferred to Petri dishes where fungal mycelium had been previously scraped with a toothpick. Each suspension was adjusted to a concentration of 106 conidia/mL using a Neubauer chamber. Fifteen µL of each isolate suspension were deposited and homogenized with C. fimbriata suspension on five sterilized microscope slides within Petri dishes containing two layers of moistened germitest paper. After 72 hours of incubation at 25 ± 1°C in a B.O.D incubator, a drop of lacto-fuchsin was deposited to halt the germination/growth process. Twenty-one isolates were tested in the pairing test, with five isolates (CT05B, CT07B, CT08A, CT13A, and CT13B) proving to be the most aggressive. Optical microscopy revealed that these five isolates inhibited the germination of C. fimbriata conidia. Therefore, it is concluded that the five isolates tested are efficient in controlling C. fimbriata in vitro.