Monitoring of virulence and phenotypes composition of Puccinia triticina population in Southern Ural in 2018
Keywords:: leaf rust, Triticum aestivum L., Triticum durum Desf., population structure, Lr-genes
The long-term monitoring of Puccinia triticina virulence on common wheat from the Southern Urals, started in 2014, was continued in 2018. Population studies have been supplemented with the data on the infectious pathogen samples collected from the durum wheat. In total, sixty isolates from each host species were studied. All isolates from the common and durum wheat were avirulent to the lines with the Lr19, Lr16, Lr24, Lr28, Lr29, Lr44 genes and virulent to the lines with Lr1, Lr3a, Lr3bg, Lr3ka, Lr14a, Lr14b, Lr17, Lr18 genes. Similarly to the previous years, the main changes in the Chelyabinsk population on the common wheat included the frequencies of virulence to Lr2a, Lr2b, Lr9, Lr11, Lr15, Lr20 and Lr26 genes. The average number of virulence alleles with respect to the 20 differentiator lines in 2018 was 13.5 and it was the lowest for the 2014–2018 period. The studied isolates from the common wheat were represented by seven virulence phenotypes. According to the indices of the genetic differences Nei (Nei D), Rogers (R) and Fst, the Chelyabinsk population in 2018 was characterized by moderate differences in comparison to 2017–2016, and higher differences in comparison to 2014–2015. Analysis of infectious populations samples collected from the durum wheat revealed significant differences among them and with pathogen samples from the common wheat. All isolates from the durum wheat were characterized by a reduced number of virulence alleles (10.5) and were avirulent to the lines with the Lr2a, Lr2b, Lr2c, Lr15 genes. A subpopulation of P. triticina from the durum wheat had a lower virulence polymorphism (TcLr20, TcLr26) and phenotypic composition (three phenotypes), compared to the subpopulation from common wheat. Under the field conditions with moderate development of leaf rust, the lines TcLr24, TcLr25, TcLr28, TcLr29, TcLr32, and TcLr37 (0 % of infection) were characterized by a high level of resistance.