Puccinia triticina Eriks., is an important fungal plant pathogen worldwide which causes wheat leaf rust and leads to considerable yield losses in Iran. New races of rust develop by mutation and selection for virulence against rust resistance genes in wheat. Studying the changes in virulence against Lr resistant genes is essential to achieve durable leaf rust resistance. Frequencies of virulence to the twenty Lr genes (Lr1, Lr2a, Lr2c, Lr3, Lr3bg, Lr3ka, Lr9, Lr10, Lr11, Lr14a, Lr14b, Lr16, Lr17, Lr18, Lr20, Lr24, Lr26, Lr28, Lr30, LrB) were compared among the regional populations of P. triticina collected from different hosts (bread wheat )Triticum aestivum Lam.), durum wheat )Triticum durum Desf.(, barley )Hordeum vulgare L.), oat )Avena sativa L.(, and triticale )Triticosecale Wittm. Ex A. Camus) and wild barley )Hordeum spontaneum Thell.() in Iran for eight years (from 2010 to 2017). Virulence to Lr1 was detected with a low frequency only in 2016 in Ardabil, Khorasan Razavi, Khuzestan, Lorestan and Mazandaran Provinces while virulence to Lr2a was not found in any studied area or year. Virulence to Lr9 was found in Mazandaran Province from 2013 and Ardabil Province from 2014 with a low frequency (one virulent pathothype) among Lr lines in all studied years. Virulence to Lr16 from 2011 to 2017 increased slightly while virulence to Lr18 was seen three times only in Khuzestan Province in 2016 and one isolate only in Fars Province in 2017. Virulence to Lr20 was found only in 2014 in Ardabil, East Azerbaijan and Mazandaran Provinces. . In 2016, Lr20-virulent pathotypes were also found in Ilam, Khuzestan and Khorasan Razavi Provinces. Thatcher isogenic line with Lr26 (TcLr26) had moderate level of resistance to Iranian isolates of P. triticina. Virulence to Lr26 was found with low frequency in 2011 and increased slightly till 2016. Virulence to Lr28 was seen only in durum wheat in Khuzestan Province in 2016 and in Fars Province on wild barley in 2017. High virulence frequencies for LrB and Lr30 were found in all studied areas and years. Virulence to Lr2c, Lr3a, Lr3bg, Lr11, Lr14b and Lr17 were observed more than other genes. The virulence frequency of leaf rust Lr genes increased from 2010 to 2017.