Oak powdery mildew (Erysiphe alphitoides)-induced volatile emissions scale with the degree of infection in Quercus robur

Abstract

Oak powdery mildew (Erysiphe alphitoides) is a major foliar pathogen of Quercus robur often infecting entire tree stands. In this study, foliage photosynthetic characteristics and constitutive and induced volatile emissions were studied in Q. robur leaves, in order to determine whether the changes in foliage physiological traits are quantitatively associated with the degree of leaf infection, and whether infection changes the light responses of physiological traits. Infection by E. alphitoides reduced net assimilation rate by 3.5-fold and isoprene emission rate by 2.4-fold, and increased stomatal conductance by 1.6-fold in leaves with the largest degree of infection of ∼60%. These alterations in physiological activity were quantitatively associated with the fraction of leaf area infected. In addition, light saturation of net assimilation and isoprene emission was reached at lower light intensity in infected leaves, and infection also reduced the initial quantum yield of isoprene emission. Infection-induced emissions of lipoxygenase pathway volatiles and monoterpenes were light-dependent and scaled positively with the degree of infection. Overall, this study indicates that the reduction of foliage photosynthetic activity and constitutive emissions and the onset of stress volatile emissions scale with the degree of infection, but also that the infection modifies the light responses of foliage physiological activities.

Induction of stress volatiles and changes in essential oil content and composition upon microwave exposure in the aromatic plant Ocimum basilicum

“…WLAN-frequency irradiation resulted in a stronger induction of VOC emissions than the GSM-frequency irradiation (Table 1), suggesting that it is a severe stress. While stress generally leads to enhanced emissions, constitutive emissions are often reduced in response to stress, especially upon severe stress (Staudt et al, 2002;Lavoir et al, 2009;Copolovici et al, 2014). In our study (Table 1), microwave-irradiated O. basilicum plants had lower emissions of β-pinene, α-phellandrene and bornyl acetate (decreased N67% compared to control).…”

“…LOX products are formed from polyunsaturated fatty acids that are released from plant membranes in different stress conditions (Feussner and Wasternack, 2002), and LOX emissions are considered to be one of the initial plant stress responses (Liavonchanka and Feussner, 2006). LOX emissions have been reported in response to drought (Permyakova et al, 2012), heat and cold (Copolovici et al, 2012), high light (Loreto et al, 2006), ozone (Beauchamp et al, 2005), leaf herbivory or mechanical damage (Allmann and Baldwin, 2010;Holopainen, 2011), fungal infections (Toome et al, 2010;Copolovici et al, 2014;Jiang et al, in press-b) and environmental pollutants including antibiotics and textile dyes . In our study, statistically significant increases in LOX compound emission were observed in the case of 3-Z-hexenol and 2-E-hexenal (about 2.5 times higher than control), indicating that microwave irradiation did lead to enhance stress status in the plants.…”

Changes in photosynthetic rate and stress volatile emissions through desiccation‐rehydration cycles in desiccation‐tolerant epiphytic filmy ferns (Hymenophyllaceae)

“…However, a plethora of volatiles is released from stressed plants (Loreto & Schnitzler, ; Matsui, Sugimoto, Kakumyan, Khorobrykh, & Mano, ; Niinemets et al, ), and the release of several of stress volatiles is typically quantitatively associated with the severity of stress (Beauchamp et al, ; Jiang, Ye, Li, & Niinemets, ; Loreto & Schnitzler, ; Niinemets, Kännaste, & Copolovici, ). Among these volatiles, the release of lipoxygenase (LOX) pathway volatiles, a mixture of various C6 aldehydes and alcohols and their derivatives, is a ubiquitous response to different abiotic and biotic stresses; LOX volatiles are typically elicited upon severe stress that leads to membrane‐level damage (Beckett et al, ; Copolovici et al, ; Copolovici, Kännaste, Pazouki, & Niinemets, ; Copolovici, Väärtnõu, Portillo Estrada, & Niinemets, ; Kanagendran, Pazouki, & Niinemets, ; Li, Harley, & Niinemets, ). The LOX pathway starts with the release of free polyunsaturated fatty acids from plant membranes, and production of a mixture of 9‐ and 13‐hydroperoxy linoleic and linolenic acids by LOXs (Andreou & Feussner, ; Liavonchanka & Feussner, ).…”

“…Among these volatiles, the release of lipoxygenase (LOX) pathway volatiles, a mixture of various C6 aldehydes and alcohols and their derivatives, is a ubiquitous response to different abiotic and biotic stresses; LOX volatiles are typically elicited upon severe stress that leads to membrane-level damage (Beckett et al, 2012;Copolovici et al, 2017;Copolovici, Kännaste, Pazouki, & Niinemets, 2012;Copolovici, Väärtnõu, Portillo Estrada, & Niinemets, 2014;Kanagendran, Pazouki, & Niinemets, 2018;Li, Harley, & Niinemets, 2017). The LOX pathway starts with the release of free polyunsaturated fatty acids from plant membranes, and production of a mixture of 9-and 13-hydroperoxy linoleic and linolenic acids by LOXs (Andreou & Feussner, 2009;Liavonchanka & Feussner, 2006).…”

Effects of oak powdery mildew (Erysiphe alphitoides [Griffon and Maubl.] U. Braun and S. Takam.) on photosynthesis of pedunculate oak (Quercus robur L.)

“…Although it has been proven and well documented that oak powdery mildew has negative effects on the photosynthesis and transpiration of leaves (Hajji et al, 2009;Pap et al, 2014;Copolovici et al, 2014), there is a further need for better understanding the effects of this obligate leaf parasite on the photosynthetic apparatus, due to its complexity. For that purpose, chlorophyll a fluorescence measurement can provide useful additional information for understanding the primary events of photosynthesis and the effects of stress on photochemistry (Razavi et al, 2008;Ajigboye et al, 2016;Guo et al, 2016;Song et al, 2018).…”