In vitro control of Botrytis cinerea and Penicillium italicum by antagonistic yeasts

Abstract

Gray mold in grapes (caused by Botrytis cinerea) and blue mold in citrus (caused by Penicillium italicum) are post-harvest diseases that cause major losses in these crops. The control of these diseases is based on the use of synthetic chemical fungicides. The increase in regulatory policies and demand to reduce the application of pesticides, due to harmful effects on the environment and humans, have led to the search for more ecofriendly alternatives, such as biological control agents. Thus, the present work aims to verify the antagonistic potential of four yeast strains, Pichia caribbica (CCMA 0759), Hanseniaspora opuntiae (CCMA 0760), Pichia manshurica (CCMA 0762), and Lachancea thermotolerans (CCMA 0763), against of B cinerea and P. italicum. To assess the antagonism of volatile compounds, Petri plates with two divisions containing potato-dextrose-agar (PDA) were used by placing a fungal mycelial disc and yeast suspension (3.0 × 106 cells mL-1) on opposite sides of the plate. The colony diameter and mycelial growth rate index of the fungi were evaluated via comparisons with the control plate without yeast. For the evaluation of the antagonism of diffusible substances in the medium, yeasts were striated 3 cm from the center of the plates containing PDA. After 48 h, a mycelial disc of each phytopathogen was placed in the center of the plates. The colony growth, inhibition halo, and mycelial growth rate index were evaluated via comparisons with the control plate. All yeast strains showed an antagonistic effect on the mycelial growth of B. cinerea in both tests. In the volatile compounds test, H. opuntiae, L. thermotolerans, P. caribbica, and P. manshurica inhibited mycelial growth by approximately 82%, 75%, 72%, and 50%, respectively. In the antagonism test of the diffusible substances in the medium, P. caribbica and P. manshurica inhibited mycelial growth by 58% and 33%, respectively. However, these yeast strains did not show an antagonistic effect against P. italicum. Thus, all isolates demonstrated potential to be tested as biocontrol agents of gray mold in post-harvest grape fruits.