Linde Celeste C, Zala Marcello, Ceccarelli Sara, McDonald Bruce A
Institute of Plant Sciences, Plant Pathology Group, Federal Institute of Technology, ETH-Zentrum, LFW, CH-8092 Zürich, Switzerland.
Fungal Genet Biol. 2003 Nov;40(2):115-25. doi: 10.1016/s1087-1845(03)00110-5.
Rhynchosporium secalis, the causal agent of scald on barley, is thought to be exclusively asexual because no teleomorph has been found. Partial sequences of the HMG-box and alpha-domain of Rhynchosporium secalis isolates were identified and used to develop a PCR assay for the mating-type locus. PCR amplification of only one of these two domains was possible in each strain, suggesting that R. secalis has a MAT organization that is similar to other known heterothallic fungi. A multiplex PCR with primers amplifying either a MAT1-1- or MAT1-2-specific amplicon was used to determine the distribution of mating types in several R. secalis populations. In total, 1101 isolates from Australia, Switzerland, Ethiopia, Scandinavia, California, and South Africa were included in the analysis. Mating types occurred in equal frequencies for most of these populations, suggesting frequency-dependent selection consistent with sexual reproduction. In addition, both mating types were frequently found occupying the same lesion or leaf, providing opportunities for isolates of opposite mating type to interact and reproduce sexually. We propose that R. secalis should be considered a sexual pathogen, although the sexual cycle may occur infrequently in some populations.
大麦网斑病菌（Rhynchosporium secalis）是大麦叶斑病的病原菌，由于未发现其有性态，因此被认为完全是无性繁殖的。对大麦网斑病菌分离株的HMG框和α结构域的部分序列进行了鉴定，并用于开发一种针对交配型位点的PCR检测方法。在每个菌株中，这两个结构域中只有一个能够进行PCR扩增，这表明大麦网斑病菌具有与其他已知异宗配合真菌相似的交配型组织。使用一对引物分别扩增MAT1-1或MAT1-2特异性扩增子的多重PCR来确定几个大麦网斑病菌群体中交配型的分布。分析共纳入了来自澳大利亚、瑞士、埃塞俄比亚、斯堪的纳维亚、加利福尼亚和南非的1101个分离株。在大多数这些群体中，两种交配型出现的频率相等，这表明存在与有性繁殖一致的频率依赖性选择。此外，经常发现两种交配型占据同一病斑或叶片，这为相反交配型的分离株进行有性相互作用和繁殖提供了机会。我们建议，尽管在某些群体中有性循环可能很少发生，但大麦网斑病菌应被视为有性病原菌。
