Monitoring of Puccinia triticina Erikss. physiologic races and effectiveness of Lr-genes in Egyptian wheat during 2014-2016 growing seasons

Abstract

Infected wheat leaves with leaf rust fungus, (Puccinia triticina), were obtained from Egyptian wheat rust trap nursery (EWRTN) located at Kafr El-Sheikh, Sharqia and Beni-Suef Governorates during 2014-15 and 2015-16 growing seasons. Leaves were used to identify virulence phenotypes prevalent in the selected Governorates. Virulence was tested with 16 lines of Thatcher wheat that differed for single leaf rust resistance (Lr) genes. The single pustule method was applied for isolation of each sample. A total of 37 and 90 virulence phenotypes were respectively described in the three Governorates during 2014-15 and 2015-16 growing seasons. The two most common virulence phenotypes across three areas were BBBB and BBBT that were high frequencies throughout the tow growing seasons. While, the other races were rare, which they represented by only one or two isolates in the tested pathogen populations. Frequency of race groups based on infection types (IT, s) of the first 8 differential host lines were also detected. The most common race group was DK-- (13.51%) which virulent to Lr 2c, 16, 24 and 26, followed by race group TT-- (10.81%) which virulent to all 8 Lr genes in 2014-15. On the other hand, race group BB-- (23.33%) was avirulent to all 8 Lr genes in 2015-16. Virulence frequency was very high against Lr 1, 2c, 10, 11, 16, 17, 21, 24 and 26. In contrast, virulence occurred at relatively low frequency against Lr 2a, 2b, 3, 3ka, 9, 18 and 30. Thus, these genes considered to be the most effective resistance genes against a large number of the pathogen isolates which were detected in the two successive growing seasons 2014-2015 and 2015-2016.