Kamel Sana, Cherif Mejda, Hafez Mohamed, Despins Therese, Aboukhaddour Reem
Laboratory of Genetics and Cereal Breeding, Department of Agronomy and Plant Biotechnology, National Agronomic Institute of Tunisia, University of Carthage, Tunis, Tunisia.
Cereal Pathology Lab, Agriculture and Agri-Food Canada, Lethbridge Research and Development Centre, Lethbridge, AB, Canada.
Front Plant Sci. 2019 Dec 18;10:1562. doi: 10.3389/fpls.2019.01562. eCollection 2019.
Tan spot is a destructive foliar wheat disease worldwide and caused by the ascomycete fungus (); it has become more frequent in Tunisia over the last decade. In this study, the virulence of 73 single-spore isolates, collected from durum and bread wheat fields during 2017-2018 growing season, was evaluated on four differential wheat genotypes. This was followed by polymerase chain reaction tests with specific primers for the effector genes , , and (-homolog). Sequence analysis to validate the identity of the amplified genes was followed, and amplicons from a subset of 22 isolates were analyzed to determine its haplotype identity. isolates from Tunisia were grouped in races 2, 4, 5, and 7, and 44% of the tested isolates did not fit under any known race, and were denoted here as atypical. These atypical isolates induced the same symptoms as race 7 isolates, extensive necrosis, and chlorosis on susceptible genotypes, but lacked the gene. is the only identified necrosis-inducing effector in , and was amplified in 51% of tested isolates, and shared identical sequence to previously identified haplotype (H15). and its homolog were present in 97% and 93% of tested isolates, respectively. in Tunisia lacked Ptr ToxC activity, and none of the tested isolates induced the specific symptoms of that effector. Race 7 and the atypical isolates dominated the Tunisian population, while races 2, 4, and 5 were found at low percentages. In conclusion, and its homolog were the most dominant genes in from Tunisia, and the majority of the isolates induced necrosis and chlorosis on Ptr ToxA and Ptr ToxB susceptible wheat genotypes. However, only about half of that necrosis can be attributed to presence, this result necessitates further research to investigate the prevalence of additional necrotic effector(s). Terminology: in this paper, abbreviated as , the effectors are referred to by Ptr ToxA, Ptr ToxB and Ptr ToxC, and the genes coding for them are written in italic as , , and , respectively.
条斑病是一种在全球范围内具有破坏性的小麦叶部病害，由子囊菌真菌（）引起；在过去十年中，它在突尼斯变得更加频繁。在本研究中，对2017 - 2018年生长季从硬粒小麦和面包小麦田采集的73个单孢分离株，在四种鉴别小麦基因型上评估了其毒力。随后使用针对效应子基因、和（-同源物）的特异性引物进行聚合酶链反应测试。接着进行序列分析以验证扩增基因的身份，并对22个分离株的子集的扩增子进行分析以确定其单倍型身份。突尼斯的分离株被分为2、4、5和7号小种，44%的测试分离株不符合任何已知小种，在此被称为非典型分离株。这些非典型分离株在感病基因型上诱导出与7号小种分离株相同的症状，即广泛的坏死和褪绿，但缺乏基因。是中唯一已鉴定的诱导坏死的效应子，在51%的测试分离株中被扩增，并且与先前鉴定的单倍型（H15）具有相同序列。和其同源物分别存在于97%和93%的测试分离株中。突尼斯的分离株缺乏Ptr ToxC活性，且没有一个测试分离株诱导出该效应子的特异性症状。7号小种和非典型分离株在突尼斯的群体中占主导地位，而2、4和5号小种的比例较低。总之，和其同源物是突尼斯分离株中最主要的基因，并且大多数分离株在对Ptr ToxA和Ptr ToxB敏感的小麦基因型上诱导坏死和褪绿。然而，只有大约一半的坏死可归因于的存在，这一结果需要进一步研究以调查其他坏死效应子的流行情况。术语：在本文中，简称为，效应子分别称为Ptr ToxA、Ptr ToxB和Ptr ToxC，编码它们的基因分别用斜体表示为、和。
