Amplified fragment length polymorphism (AFLP) analysis was used to investigate the genetic diversity in isolates of the ectomycorrhizal fungus Cenococcum geophilum from serpentine and non-serpentine soils in Portugal. A high degree of genetic diversity was found among C. geophilum isolates; AFLP fingerprints showed that all the isolates were genetically distinct. We also assessed the in vitro Ni sensitivity in three serpentine isolates and one non-serpentine isolate. Only the non-serpentine isolate was significantly affected by the addition of Ni to the growth medium. At 30 microg g(-1) Ni, radial growth rate and biomass accumulation decreased to 73.3 and 71.6% of control, respectively, a highly significant inhibitory effect. Nickel at this concentration had no significant inhibitory effect on serpentine isolates, and so the fitness of serpentine isolates, as evaluated by radial growth rate and biomass yield, is likely unaffected by Ni in the field. In all isolates, the Ni concentration in the mycelia increased with increasing Ni concentration in the growth medium, but two profiles of Ni accumulation were identified. One serpentine isolate showed a linear trend of Ni accumulation. At the highest Ni exposure, the concentration of Ni in the mycelium of this isolate was in the hyperaccumulation range for Ni as defined for higher plants. In the remaining isolates, Ni accumulation was less pronounced and seems to approach a plateau at 30 microg g(-1) Ni. Because two profiles of Ni accumulation emerged among our Ni-insensitive serpentine isolates, this result suggests that different Ni detoxification pathways may be operating. The non-serpentine isolate whose growth was significantly affected by Ni was separated from the other isolates in the genetic analysis, suggesting a genetic basis for the Ni-sensitivity trait. This hypothesis is further supported by the fact that all isolates were maintained on medium without added Ni to avoid carry-over effects. However, because AFLP analysis failed to distinguish between serpentine and non-serpentine isolates, we cannot conclude that Ni insensitivity among our serpentine isolates is due to evolutionary adaptation. Screening a larger number of isolates, from different geographical origins and environments, should clarify the relationships between genetic diversity, morphology, and physiology in this important species.

译文

:扩增片段长度多态性(AFLP)分析用于研究葡萄牙蛇纹石和非蛇纹石土壤中的外生菌根真菌Cenococcum geophilum分离株的遗传多样性。在嗜水梭状芽孢杆菌分离物中发现了高度的遗传多样性。 AFLP指纹图谱显示所有分离株在基因上都是不同的。我们还评估了三种蛇形分离株和一种非蛇形分离株的体外镍敏感性。在生长培养基中添加镍只会显着影响非蛇纹石分离株。在30 microg g(-1)Ni下,放射状生长速率和生物量积累分别降至对照的73.3和71.6%,这是一个非常显着的抑制作用。此浓度的镍对蛇纹石分离物没有明显的抑制作用,因此,通过径向生长速率和生物量产量评估,蛇纹石分离物的适应性很可能不受田间镍的影响。在所有分离物中,菌丝体中的镍浓度随着生长培养基中镍浓度的增加而增加,但是鉴定出两种镍积累曲线。一种蛇形分离株显示出镍积累的线性趋势。在最高的Ni暴露水平下,此分离株菌丝体中的Ni浓度在高聚植物的累积范围内。在其余的分离物中,Ni的积累不那么明显,并且似乎在30 microg g(-1)Ni时接近平稳状态。由于在我们对镍不敏感的蛇形分离株中出现了两个镍积累曲线,因此该结果表明可能存在不同的镍解毒途径。在基因分析中,其生长受到镍显着影响的非蛇形分离株与其他分离株是分离的,这为镍敏感性特征提供了遗传基础。所有分离物均保持在不添加镍以避免残留效应的培养基上的事实进一步支持了该假设。但是,由于AFLP分析无法区分蛇纹石和非蛇纹石分离株,因此我们不能得出结论,我们的蛇纹石分离株中Ni不敏感是由于进化适应。筛选来自不同地理起源和环境的大量分离株,应阐明该重要物种的遗传多样性,形态和生理之间的关系。

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