Photosynthetic and antioxidative alterations in coffee leaves caused by epoxiconazole and pyraclostrobin sprays and Hemileia vastatrix infection

Abstract

Coffee leaf rust (CLR), caused by Hemileia vastatrix, is a major disease affecting coffee production worldwide. In this study, an in-depth analysis of the photosynthetic performance of coffee leaves challenged or not with H. vastatrix and sprayed with either epoxiconazole (EPO) or pyraclostrobin (PYR) was performed by combining chlorophyll a fluorescence images, photosynthetic pigment pools and the activities of chitinase (CHI), β-1,3-glucanase (GLU), peroxidase (POX) and catalase (CAT). The CLR severity was higher in the control plants, but reduced in plants sprayed with both PYR and EPO. Also, the CLR severity was reduced in plants sprayed with PYR compared with plants sprayed with EPO. Plants sprayed with either EPO or PYR showed maximal photosystem II quantum efficiency (Fv/Fm) values ranging from 0.78 to 0.80, which were quite similar to those obtained with inoculated plants (values ranging from 0.74 to 0.77). The decreases in the Fv/Fm ratio values and parallel increases in the F0 values in the inoculated plants, which were not observed in the control plants (sprayed with water) and were confirmed by images of the initial fluorescence (F0) and Fv/Fm parameters in the regions of the leaf tissue containing pustules and in the asymptomatic leaf tissue, indicated that photosynthesis was negatively impacted. When effective photosystem II quantum yield (Y(II)) values approached zero with a high photosynthetic photon flux density, high values of quantum yield of regulated energy dissipation (Y(NPQ)) in association with a high carotenoid concentration were noted in the inoculated plants sprayed either with PYR or EPO. The increased CLR severity in inoculated plants in contrast to inoculated plants sprayed with either PYR or EPO was associated with greater POX activity and a reduced photosynthetic pigment concentration. POX and CAT activities were increased in inoculated plants sprayed with either EPO or PYR when compared with control plants. CHI and GLU activities were maintained at high levels in the leaves of inoculated plants, regardless of the fungicide sprayed, indicating that CHI and GLU are less important for coffee resistance against CLR. The results of the present study clearly demonstrated that plants sprayed with either EPO or PYR showed milder CLR symptoms with adequate photosynthetic performance and optimal conditioning of their antioxidant systems.

Leaf gas exchange and chlorophyll a fluorescence in soybean leaves infected by Phakopsora pachyrhizi

“…pachyrhizi , the F v / F m values remained closer to the ones obtained from non‐inoculated counterparts indicating a positive effect of the fungicide in counteract the deleterious effect of fungal infection on photosynthesis. The reduction of coffee leaf rust severity in coffee plants sprayed with Epo+Pyr was accompanied by a better photosynthetic capacity of the infected plants due to a lower photochemical damage as indicated by the higher values for F 0 , F m and F v / F m (Honorato Junior, Zambolim, Aucique‐Perez, Resende, & Rodrigues, ). For soybean plants sprayed with ASM and infected with P .…”

“…Additionally, high concentration of Chl a + b would lead to an increase in the ability and efficiency of the leaves to capture energy needed for the photochemical reactions involved on photosynthesis (Buchenauer & Rohner, ). Reduction in the concentration of pigments on the leaves of soybean plants infected with P. pachyrhizi as well as for other host‐pathogen interactions such as Phakopsora pachyrhizi on soybean, Pyricularia oryzae on wheat, Stenocarpella macrospora on maize and Hemileia vastatrix on coffee has been reported (Bermúdez‐Cardona, Wordell Filho, & Rodrigues, ; Honorato Junior, Zambolim, Aucique‐Perez, Resende, & Rodrigues, ; Kumudini, Prior, Omielan, & Tollenaar, ; Rios, Rodrigues, Debona, & Silva, ).…”

“…The F m and F v /F m (Honorato Junior, Zambolim, Aucique-Perez, Resende, & Rodrigues, 2015). For soybean plants sprayed with ASM and infected with P. pachyrhizi, the F 0 , F m and F v /F m values showed minor reductions in comparison with plants from the control treatment and infected with P. pachyrhizi indicating, therefore, a delay in the occurrence of damage to the photosystems.…”

Photoynthetic and productive increase in tomato plants treated with strobilurins and carboxamides for the control of Alternaria solani

“…Resulting in greater absorption of sunlight and, consequently, greater ETR values , as observed for Flux + Pyra, followed by Me + Pyra treatments. Increases in the content of photosynthetic pigments were also reported in tomato with the application of pyraclostrobin plus boscalid (Ramos et al, 2015) and coffee with application of pyraclostrobin (Honorato Júnior et al, 2015), reflecting higher photosynthetic efficiency of plants, in addition to the increase of the repair and protection of the photosynthetic apparatus by carotenoids (Nisar et al, 2015).…”

Cambios bioquímicos en respuesta al ataque de roya en plantaciones de café

“…De acuerdo con González et al (2011), la actividad enzimática de la glucanasa es una de las más importantes en el fenómeno de la resistencia vegetal ya que interviene en la degradación de los glucanos de la pared celular fúngica. Así mismo, Honorato et al (2015) demostraron que la actividad de la glucanasa en las plantas se eleva en los días en torno a la infección de la roya desde el día 2 hasta el día 40, caso contrario a lo que se demuestra con las plantas control que no están infectadas. Monteiro et al, (2016) mostraron que las plantas de café ante la incidencia de la roya en las primeras 24 horas, hay un incremento de la expresión de la enzima glucanasa.…”