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.

Annotation

The ability to effectively protect orchards against apple scab is threatened by Venturia inaequalis developing resistance to fungicides with a particular mode of action. Three pathogen populations from orchards in the Krasnodar region were used in dose-effect tests to examine the susceptibility of the apple scab pathogen population to cyprodinil. One of the populations was collected in an abandoned garden and was the baseline. The rest of the populations are collected in commercial gardens with the annual use of fungicides, including cyprodinil. The effect of 7 concentrations of cyprodinil was determined: 0.001, 0.01; 0.10; 0.50; 1.00; 10.00 and 50.00 mg/l for the growth of monospore pathogen isolates on Leroux synthetic medium. A total of 63 fungus isolates were analyzed. The growth of mycelium on the fungicide was expressed as a percentage relative to the control variant of the medium. The concentration of fungicide active ingredient that resulted in a two-fold inhibition of growth, called the effective 50 % concentration (EC50), was found using a probit regression transformation of the relative mycelial growth on the active ingredient. Analysis of dose-effect curves showed hormetic responses at low fungicide concentrations. The results of the study revealed that the sensitivity of the original population was significantly higher than that of the two fungicidal populations at a significance level of p

Annotation

In the protection of fruit crops from a complex of pathogens, one of the current tasks is to prevent the development of root rot, among the causes of which are the activity of soil micromycetes Phytophthora sp. Selective media play a key role both in identification and subsequent storage in the laboratory, and in the study of morphological and cultural traits, sporulation ability, as well as to obtain a certain amount of inoculum (for example, for in vivo studies) and mycelium (for DNA isolation). Obtaining a pure culture of pathogenic micromycete with certain morphological and cultural characteristics, which may be important for diagnosis by both traditional and modern methods, determines the relevance of studying the influence of various media on these parameters of the pathogenic fungus Phytophthora sp. The studies were carried out by methods of laboratory and comparative analyses. The growth of the pathogen strain of apple root rot Phytophthora sp. on nine nutrient media was studied. The colony growth rate and morphological and cultural characteristics were evaluated. As a result of the research, the strain has been found to vary not only the growth rate of the colony, but also the cultural characteristics depending on the nutrient medium. Of the nine nutrient media, three universal ones were selected that are most suitable for cultivation and identification, namely, tomato, potato-glucose and must agars. They meet the following criteria: ensuring the maximum degree of sporulation, rapid growth and development of the mycelium of the fungus, ease of preparation. It was also noted that Leroux medium can be used to obtain a large amount of inoculum, since it will produce more spores when planted in a lawn than on other media.