Wheat blast, caused by Pyricularia oryzae, is currently the main disease that threat to food security and wheat production in the world. This study investigated the photosynthetic responses of wheat plants from cultivars BR‐18 (moderately resistant) and BRS‐Guamirim (susceptible), differing in their levels of resistance to blast, by using leaf gas exchange and rapid light curves analysis focusing primarily on the asymptomatic (AS) and symptomatic (S) phases of disease development. The photosynthetic capacity of plants from cultivar BRS‐Guamirim was compromised by diffusional CO₂ limitations and inefficient photoprotection mechanism at the AS phase of blast due to reductions in CO₂ assimilation, stomatal conductance, transpiration rate and fluorescent quantum efficiency (F_v/F_m). For cultivar BR‐18, the loss in photosynthesis was minimized due to an efficient control in the regulated energy dissipation [Y(NPQ)] avoiding losses by latent heat [Y(NO)]. Additionally, F_v/F_m was a promissory physiological indicator of blast during its AS phase while Y(NPQ) and Y(NO) were more sensitive at the S phase of the disease. In conclusion, the physiological parameters F_v/F_m, Y(NQP) and Y(NO) can be used as physiological markers in wheat breeding programs seeking in the development of cultivars resistant to blast.

中文翻译：

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小麦抗稻瘟病水平的光合变化

由稻瘟病菌引起的小麦瘟病是目前威胁世界粮食安全和小麦生产的主要疾病。这项研究通过使用叶片气体交换和快速光曲线分析（主要针对无症状）研究了BR-18（中度抗病）和BRS-Guamirim（易感）小麦植物的光合响应，不同之处在于它们对稻瘟病的抗性水平不同。 （AS）和症状（S）阶段的疾病发展。来自BRS-Guamirim品种的植物的光合作用能力受到扩散的CO ₂限制和高能植物在AS阶段由于CO ₂减少而导致的光保护机制效率低下的损害。同化，气孔导度，蒸腾速率和荧光量子效率（F _v / F _m）。对于BR-18品种，由于有效控制了调节的能量耗散[Y（NPQ）]，避免了潜热[Y（NO）]的损失，因此光合作用的损失得以最小化。此外，F _v / F _m是在其AS阶段爆炸的一种顺应性生理指标，而Y（NPQ）和Y（NO）在疾病的S阶段更为敏感。总之，生理参数F _v / F _m，Y（NQP）和Y（NO）可用作小麦育种计划中的生理标记，以寻求抗稻瘟病品种的发展。