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Research on Crops

Effect of repeated treatments with a two-component fungicide based on active ingredients from the triazole and strobilurin classes on the virulence of Puccinia hordei isolates in southern Russia


DOI: 10.31830/2348-7542.2026.ROC-1309    | Article Id: ROC-1309 | Page : 343-349
Citation :- Effect of repeated treatments with a two-component fungicide based on active ingredients from the triazole and strobilurin classes on the virulence of Puccinia hordei isolates in southern Russia. Res. Crop. 27: 343-349
OLGA KUDINOVA, MARIA GVOZDEVA, VALERIA RUDENKO AND GALINA VOLKOVA alosa@list.ru
Address : Federal State Budgetary Scientific Institution «Federal Research Center of Biological Plant Protection» (FSBSI FRCBPP), Krasnodar, 350039, Russia
Submitted Date : 16-04-2026
Accepted Date : 7-05-2026
Online Published:

Abstract

Resistance of pest populations to fungicide active ingredients is a serious problem for crop production. One of the factors contributing to the development of resistance is the use of fungicides at rates below the recommended application rates and repeated applications of fungicides. According to the literature, this can lead to the selection of virulent pathogen isolates. The purpose of this study was to test the hypothesis of the selection of virulent Puccinia hordei isolates under the influence of repeated applications at reduced rates of the fungicide Baliy, MEC (active ingredient: 120 g/l azoxystrobin + 180 g/l propiconazole). The study was conducted in the greenhouse complex of the Federal Research Center of Biological Plant Protection in 2025. Thirty isolates of the North Caucasus population of P. hordei with known virulence were used in the study. Sixteen barley lines containing known Rph resistance genes were used to study the virulence. The plants of the susceptible barley variety Vivat, infected with fungal isolates, were treated with the fungicide Baliy, MEC at a rate of 50% of the recommended application rate (0.3 l/ha). A total of three treatments were performed, and the virulence of 99 P. hordei isolates was studied, of which 97 unique phenotypes were identified. A general trend of a decrease in the frequency of isolates to most lines with Rph genes was observed after the first and second applications of the fungicide. However, an increase in the frequency of isolates to Rph9, Rph14, and Rph19 was observed after the first application, and to Rph3 and Rph9 after the second application. After the third application, 20 fungal isolates ceased to sporulate, and the remaining 10 isolates exhibited high virulence, with an increase in the frequency of isolates infecting lines with Rph1, Rph3, Rph4, Rph5, Rph6, Rph12, Rph14, Rph19, Rph21, Rph25, and Rph27 genes. Therefore, reducing the dosage of the fungicide and performing repeated applications can contribute to the selection of virulent isolates, making strict adherence to the recommended application rates crucial for sustainable barley protection and preventing resistance.

Keywords

Barley barley leaf rust fungicides Puccinia hordei resistance fungicides virulence.

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