Fruit growing
and viticulture of South Russia

Annotation

To develop protective measures, it is necessary to identify the most dangerous and new harmful objects, as well as to select drugs with high efficiency. However, it is not always possible to assess the effectiveness of inhibition of a particular fungus species by chemical preparations; in addition, many phytopathogens can acquire a certain level of resistance to fungicides. For this reason, it becomes necessary to study the effectiveness of drugs against individual species using laboratory methods using pure cultures of fungi. The in vitro method makes it possible to evaluate the effectiveness of chemical preparations against pathogens in a fairly short time. However, there is the problem of the lack of a standardized method for assessing antifungal activity against economically important pathogens of agricultural crops. The studies were performed by two methods depending on the method of introducing the drug into the medium: by agar stab technique with a uniform introduction of the drug onto the surface of the nutrient medium and by inoculation the conidial suspension of the pathogen with a microbiological spatula when the drug is introduced on paper disks. The antifungal activity of chemicals against the fungus Alternaria alternata, the causative agent of apple fruit rot, varied in a wide range from no effect to strong, but in most variants of the experiment it was medium and the data obtained by the two methods of study were comparable. Comparison of these two methods showed a different degree of reproducibility of the results. So the most stable and repeatable results were given by the method with a uniform application of the working concentration of the drug to the surface of the nutrient medium and sowing by injection. In our study, the disk-diffusion method turned out to be more laborious, and the effects obtained by this method were not always characterized by an unambiguous interpretation and differed in repetitions, in comparison with the method in which the fungicide was applied directly to the agar plate, and the sowing was carried out by agar stab technique. Further optimization and standardization of this method is needed, including the amount of fungal inoculum applied and the thickness and evenness of the agar plate.