The vast oak-dominated forests of the Zagros Mountains in southwestern Iran currently undergo large-scale dieback driven by a combination of drought and increasing incidence of charcoal disease caused by the fungal pathogens Biscogniauxia mediterranea and Obolarina persica. Here, we explore the interactive effects between drought and charcoal disease agents on the physiology and biochemistry of Quercus infectoria and Quercus libani seedlings. The combination of pathogen attack and water limitation hampered plant development, especially in Q. libani seedlings, negatively affecting growth, biomass production, photosynthetic efficiency, and leaf water potential. An increase in markers of oxidative damage together with the upregulation of the antioxidant defence revealed that drought stress and pathogen infection led to pro-oxidative conditions in both oak species, especially in Q. libani, where larger changes in malondialdehyde and hydrogen peroxide occurred. The upregulation of the antioxidant system was more prominent in Q. infectoria than in Q. libani, resulting in enhanced enzyme activity and accumulation of non-enzymatic antioxidants. Fungal infection stimulated the activity of chitinase, phenylalanine ammonia lyase and β-1,3-glucanase in Q. infectoria leaves and this response became more pronounced under water shortage. Our study highlights that drought stress greatly intensifies the effects of the charcoal disease. Moreover, our findings imply superior stress resistance of Q. infectoria conferred by a highly efficient antioxidant system, strong osmotic adjustment (through proline), and increases in resistance enzymes and secondary metabolites (phenols and flavonoids). Future investigations should focus on adult trees in their natural habitat including interactions with soil factors and other pathogens like nematodes, bacteria and other fungi. Since the present research was conducted on oak seedlings, the findings can be considered by forest nursery managers. This article is protected by copyright. All rights reserved.

中文翻译：

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Quercus infectoria和Q. libani对干旱和木炭病的不同生理生化反应

伊朗西南部扎格罗斯山脉以橡树为主的广阔森林目前正在经历大规模枯死，这是由于干旱和由真菌病原体 Biscogniauxia mediterranea 和 Obolarina persica 引起的木炭病发病率增加的共同驱动。在这里，我们探讨了干旱和木炭病因子之间对 Quercus infectoria 和 Quercus libani 幼苗生理和生物化学的相互作用。病原体攻击和水分限制的结合阻碍了植物发育，特别是在 Q. libani 幼苗中，对生长、生物量生产、光合效率和叶水势产生负面影响。氧化损伤标志物的增加以及抗氧化防御的上调表明，干旱胁迫和病原体感染导致两种橡树物种的促氧化条件，特别是在 Q. libani 中，丙二醛和过氧化氢发生了更大的变化。抗氧化系统的上调在 Q. infectoria 中比在 Q. libani 中更为突出，导致酶活性增强和非酶抗氧化剂的积累。真菌感染刺激了 Q. infectoria 叶子中几丁质酶、苯丙氨酸解氨酶和 β-1,3-葡聚糖酶的活性，这种反应在缺水情况下变得更加明显。我们的研究强调，干旱压力极大地加剧了木炭病的影响。此外，我们的研究结果表明 Q 具有优越的抗压性。由高效抗氧化系统、强渗透调节（通过脯氨酸）以及抗性酶和次级代谢物（酚类和黄酮类化合物）的增加赋予的感染。未来的调查应侧重于自然栖息地中的成年树木，包括与土壤因素和其他病原体（如线虫、细菌和其他真菌）的相互作用。由于目前的研究是在橡树幼苗上进行的，因此森林苗圃经理可以考虑这些发现。本文受版权保护。版权所有。未来的调查应侧重于自然栖息地中的成年树木，包括与土壤因素和其他病原体（如线虫、细菌和其他真菌）的相互作用。由于目前的研究是在橡树幼苗上进行的，因此森林苗圃经理可以考虑这些发现。本文受版权保护。版权所有。未来的调查应侧重于自然栖息地中的成年树木，包括与土壤因素和其他病原体（如线虫、细菌和其他真菌）的相互作用。由于目前的研究是在橡树幼苗上进行的，因此森林苗圃经理可以考虑这些发现。本文受版权保护。版权所有。