Damasceno-Silva K J, Souza E A, Freire C N S, Ishikawa F H
Embrapa Meio-Norte, Teresina, PI, Brasil.
Universidade Federal de Lavras, Laboratório de Resistência de Plantas a Doenças e Genética Molecular,
Genet Mol Res. 2015 Jul 3;14(3):7436-45. doi: 10.4238/2015.July.3.19.
The fungus Pseudocercospora griseola is the causal agent of angular leaf spot, a common bean (Phaseolus vulgaris L.) disease. The successful development of angular leaf spot-resistant cultivars depends on understanding the levels of variability in pathogen populations. P. griseola shows great pathogenic and genetic variation using inoculation on differential bean cultivars and molecular markers. Nevertheless, how this variability develops is not clearly understood. Parasexuality has been presented as a mechanism used by asexual fungi to increase variation. Hyphal fusion is the first step for the parasexual cycle, and it can be considered an additional trait for population studies. The aim of this study was to identify hyphal fusion (anastomosis) among P. grisola isolates and to evaluate the variability of isolates using analyses of anastomosis groups and RAPD markers. Hyphal anastomosis was observed in all isolates. Three isolates showed 85.0% compatibility and were compatible with 17 isolates. This is the first report of the occurrence of anastomosis between P. griseola isolates. Sixteen anastomosis groups were observed and only one group was formed by five isolates (Pg-01, Pg-02, Pg-07, Pg-08, and Pg-12). There was a large number of anastomosis groups and absence of clustering among isolates for hyphal fusion, demonstrating the existence of genetic variability for loci involved in the control of this trait. High genotypic variability by RAPD markers was detected, but there was no relationship between genotype and anastomosis group. More studies are necessary to elucidate further the process of asexual recombination in this phytopathogen.
灰拟尾孢菌是菜豆角斑病的致病因子，菜豆角斑病是普通菜豆（Phaseolus vulgaris L.）的一种病害。抗角斑病品种的成功培育取决于对病原菌群体变异水平的了解。通过接种鉴别菜豆品种和利用分子标记，灰拟尾孢菌表现出很大的致病性和遗传变异。然而，这种变异是如何产生的尚不清楚。准性生殖已被认为是无性真菌增加变异的一种机制。菌丝融合是准性生殖周期的第一步，可被视为群体研究的一个附加性状。本研究的目的是鉴定灰拟尾孢菌分离株之间的菌丝融合（吻合）情况，并通过吻合群分析和随机扩增多态性DNA（RAPD）标记评估分离株的变异性。在所有分离株中均观察到菌丝吻合。三个分离株表现出85.0%的相容性，并与17个分离株相容。这是关于灰拟尾孢菌分离株之间发生吻合的首次报道。观察到16个吻合群，只有一个群由五个分离株（Pg - 01、Pg - 02、Pg - 07、Pg - 08和Pg - 12）组成。菌丝融合的吻合群数量众多且分离株之间无聚类现象，表明控制该性状的基因座存在遗传变异性。通过RAPD标记检测到高度的基因型变异性，但基因型与吻合群之间没有关系。需要更多研究来进一步阐明这种植物病原菌的无性重组过程。
