Background and aims

There is little information about the role of fungal endophytes on plant performance under oxygen-limited conditions. This study aimed to investigate the effect of Epichloë endophyte symbiosis on tall fescue responses to oxygen stress in a greenhouse experiment.

Methods

The experiment was conducted with seven air-filled porosity levels in a sandy loam soil using genotypes (75C and 75B) of tall fescue (Festuca arundinacea) infected with and without endophytic fungus Epichlöe coenophiala (E+ and E–, respectively). Growth and physiological variables were determined to characterize plant response to oxygen-limited conditions, after nine-month application of the treatments.

Results

The results showed that E+ 75B plants benefited from endophytic symbiosis in all air-filled porosity levels, showing a higher plant biomass, better water status and lower catalase and ascorbate peroxidase activity than E– 75B plants. In contrast, a reverse trend was observed for the genotype 75C. The E– plants also coped with poor aeration by forming adventitious roots at the soil surface, aerenchyma formation within the root tissue, and increased alcohol dehydrogenase activity.

Conclusions

The presence of endophyte improved the genotype 75B performance under anaerobic conditions, while endophyte had an adverse effect on the performance of genotype 75C. This is probably due to incompatibility between Epichlöe endophyte and genotype 75C. Epichloë endophyte is likely to decrease the flooding-induced oxidative stress and prevented the over-accumulation of reactive oxygen species in the genotype 75B. Epichloë endophyte probably maintained oxidative conditions around the roots, and consequently, E+ plants required lower level of flooding-tolerance mechanisms.

中文翻译：

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Epichloë 真菌内生菌共生对高羊茅以应对洪水导致的缺氧条件的影响取决于宿主基因型

背景和目标

关于内生真菌在缺氧条件下对植物性能的作用的信息很少。本研究旨在在温室实验中研究Epichloë内生菌共生对高羊茅对氧胁迫反应的影响。

方法

使用感染和未感染内生真菌Epichlöe coenophiala（分别为 E+ 和 E- ）的高羊茅（Festuca arundinacea）的基因型（75C 和 75B），在砂质壤土中进行了七个充气孔隙度水平的实验。在应用治疗 9 个月后，确定了生长和生理变量来表征植物对氧气限制条件的反应。

结果

结果表明，与 E-75B 植物相比，E+75B​​ 植物在所有充气孔隙度水平下均受益于内生共生，显示出更高的植物生物量、更好的水分状况以及更低的过氧化氢酶和抗坏血酸过氧化物酶活性。相反，观察到基因型 75C 的相反趋势。E- 植物还通过在土壤表面形成不定根、在根组织内形成通气组织和增加乙醇脱氢酶活性来应对通气不良。

结论

内生菌的存在改善了基因型 75B 在厌氧条件下的性能，而内生菌对基因型 75C 的性能有不利影响。这可能是由于Epichlöe内生菌和基因型 75C之间的不相容性。Epichloë内生菌可能会降低洪水引起的氧化应激，并防止基因型 75B 中活性氧的过度积累。Epichloë内生菌可能维持根部周围的氧化条件，因此，E+ 植物需要较低水平的耐淹机制。