In vitro screening for the antagonistic activity of yeast strains against the apple scab pathogen Venturia inaequalis (Cooke) G. Winter

Apple scab (caused by Venturia inaequalis (Cooke) G. Winter) is one of the most harmful diseases of this crop. Therefore, when cultivating susceptible cultivars, it is necessary to implement a set of protective measures based on fungicide use. This increases the cost of the output and reduces the environmental friendliness of production. Consequently, alternative control methods are currently being sought. One such promising approach involves utilizing biological agents which have an antagonistic effect on the scab pathogen. The article examines the prospects of using yeast as a biological agent to suppress the scab pathogen. The study aims to evaluate the antagonistic activity of yeast strains against the pathogen V. inaequalis under microbiological culture conditions. The research objects were yeast strains of the Saccharomyces cerevisiae species and the non-Saccharomyces genera. A total of 34 isolates was obtained from the surface of grape berries selected in the vineyards of Krasnodar Krai. Another object was an apple scab strain isolated from scab-affected leaves. The antagonistic activity of yeast was evaluated using the dual culture technique on an agarized peptone-yeast medium. As a result, the research identified the antagonistic effects of several studied yeast strains on the scab pathogen. The colony diameter of the pathogen culture ranged from 19.0 (nS23) to 29.3 mm (S1, S8) depending on the antagonistic activity of the yeast strains. In the controls, this figure equaled 35.6 mm. Taking into account the average values, the non-Saccharomyces genera strains had a stronger antagonistic effect on V. inaequalis , unlike the Saccharomyces cerevisiae strains. The inhibitory activity evaluation enabled the identification of strains nS22, nS23, nS26, nS27 which exhibited inhibitory capacity of 43.8–46.6 %. Subsequent studies of the ability of strains nS22, nS23, nS26, nS27 to suppress V. inaequalis bioactivity under orchard coenosis conditions may further confirm their antagonistic properties. As a result, it will be possible to propose strains for developing biofungicides to combat apple scab.