Evaluación in vitro de cepas de Bacillus spp., para el control de Colletotrichum gloeosporioides y Botrytis cinerea

Abstract

In Ecuador, the agricultural sector faces an increasing phytosanitary problem caused by the fungi Botrytis cinerea and Colletotrichum gloeosporioides, which has led to the irrational use of chemical compounds and economic losses in Vitis vinifera and Theobroma cacao crops. Therefore, the aim of this study was to evaluate, through an in vitro assay, Bacillus spp. Strains for the control of the phytopathogenic fungi C. gloeosporioides and B. cinerea. Five strains of the genus Bacillus (AEC-00215, AEC-00256, AEC-00257, AEC-00258 and AEC-00259) at a concentration of 1x10*7 CFU/mL were evaluated against fungal isolates of B. cinerea from Vitis vinifera and C. gloeosporioides from Theobroma cacao using dual culture assays, with a total of 18 experimental units per fungus. A 20 % quaternary ammonium solution was used as a positive control and water as a negative control. Each fungus was inoculated in the center of Petri dishes containing malt extract agar and incubated for 24 and 48 hours at 28 ± 2 °C, while bacterial strains were cultured in LuriaBertani broth and incubated overnight at 35 ± 2 °C. After 48 and 72 hours of fungal incubation, bacterial strains were placed in a triangular arrangement around the mycelial growth. Fungal radial growth was measured on the seventh day of incubation, and the percentage of radial growth inhibition was calculated. Statistical analyses confirmed that all five bacterial strains inhibited the growth of both phytopathogenic fungi, with Bacillus subtilis (AEC-00258) showing the highest inhibition against B. cinerea (73,98 %) and Bacillus amyloliquefaciens (AEC-00259) being the most effective against C. gloeosporioides (69,05 %). These results demonstrate that Bacillus spp. is highly effective as a biocontrol agent under laboratory conditions, highlighting its potential application for preventive treatments during the preharvest stage.