Laboratoire Biotechnologie des Micro-organismes, GIS PhyNoPi, Institut Supérieur d'Agriculture, 48 Boulevard Vauban, F-59046 Lille cedex, France.
Fungal Biol. 2010 Nov-Dec;114(11-12):980-90. doi: 10.1016/j.funbio.2010.09.008. Epub 2010 Sep 29.
Septoria tritici blotch caused by the heterothallic ascomycete Mycosphaerella graminicola is currently the most frequent and the most economically damaging disease on wheat worldwide. Five hundred and ten strains of this fungus were sampled from 16 geographical locations representing the major wheat producing areas in France. Multiplex PCR amplification, PCR-RFLP-SSCP screening and sequencing of parts of mating type encoding sequences were performed in order to assess the distribution and molecular polymorphism of the mating type idiomorphs. The two idiomorphs were scored at similar frequencies within all sampled locations. Both mating types were also identified at the leaf spatial scale, on 42% of leaves from which two or three strains were isolated. No correlation was found between distribution of mating types and either host cultivars from which the sampling was carried out or in vitro colony phenotypes observed during the culture of strains on potato dextrose agar (PDA) medium. PCR-RFLP-SSCP assay highlighted only one MAT1-1 strain exhibiting a profile distinct from all other MAT1-1 strains, whereas ten MAT1-2 strains (among which two and four with same profiles, respectively) showed profiles differing from the other MAT1-2 strains. Sequencing revealed that all polymorphisms corresponded to single nucleotide variations and all strains displaying the same single strand conformation polymorphism (SSCP) profiles showed identical nucleotide sequences, thereby confirming the high sensitivity of SSCP. Only two out of the disclosed nucleotide variations were nonsynonymous. This study strongly suggests a large potential for sexual reproduction in the French population of M. graminicola and reports a high conservation of mating type sequences in the fungus at both nucleotide and population levels, with a great difference in molecular variability between the two idiomorphs.
小麦叶枯病菌引起的叶枯病是目前世界范围内小麦上最普遍和最具经济危害性的病害。本研究从法国 16 个主要小麦种植区采集了 510 株该病原菌。通过多重 PCR 扩增、PCR-RFLP-SSCP 筛选和交配型编码序列部分测序，评估了交配型异型的分布和分子多态性。在所有采样地点，两个异型的评分频率相似。在叶的空间尺度上，也在 42%的叶片上鉴定到了两种交配型，从这些叶片上分离到了两到三个菌株。在采样所涉及的宿主品种或在马铃薯葡萄糖琼脂（PDA）培养基上培养菌株时观察到的体外菌落表型之间，没有发现交配型的分布与两者之间存在相关性。PCR-RFLP-SSCP 分析仅突出了一个 MAT1-1 菌株，其图谱与所有其他 MAT1-1 菌株明显不同，而 10 株 MAT1-2 菌株（其中两个和四个分别具有相同的图谱）显示出与其他 MAT1-2 菌株不同的图谱。测序表明，所有多态性均对应于单个核苷酸变化，并且显示相同单链构象多态性（SSCP）图谱的所有菌株均显示出相同的核苷酸序列，从而证实了 SSCP 的高灵敏度。所揭示的核苷酸变异中只有两个是非同义的。本研究强烈表明，法国小麦叶枯病菌群体中存在很大的有性繁殖潜力，并报告了该真菌在核苷酸和种群水平上的交配型序列高度保守，两个异型之间的分子变异性差异很大。
