biologia plantarum

Biologia plantarum 63:643-653, 2019 | DOI: 10.32615/bp.2019.130

Changes in leaf gas exchange, chlorophyll a fluorescence, and antioxidantsin maize leaves infected by Exserohilum turcicum

P.R. SILVEIRA¹, P.O. MILAGRES¹, E.F. CORRÊA¹, C.E. AUCIQUE-PÉREZ¹, J.A. WORDELL FILHO², F.A. RODRIGUES^1,*

¹ Universidade Federal de Viçosa, Departamento de Fitopatologia, Laboratório da Interação Planta-Patógeno, Viçosa, Minas Gerais, 36570-900, Brazil

² EPAGRI/CEPAF, Laboratório de Fitossanidade, Chapecó, Santa Catarina, 89801-970, Brazil

Considering the importance of northern leaf blight, caused by Exserohilum turcicum, to decrease maize yield, this study evaluated electrolyte leakage, content of H₂O₂, malondialdehyde (MDA), chlorophyll (Chl) a, Chl b, and carotenoids (CAR), and activities of superoxide dismutase, catalase, ascorbate peroxidase, peroxidase, glutathione reductase, glutathione-S-transferase, and glutathione peroxidase, as well as expressions of superoxide dismutase (sod), catalase (cat 1), ascorbate peroxidase (apx 2), peroxidase (pox), glutathione reductase (gr 1), and glutathione-S-transferase (gst 23) genes, and leaf gas exchange and Chl a fluorescence parameters in maize leaves infected with E. turcicum. The content of H₂O₂ and MDA was high at 15 and 20 d after inoculation (dai) and electrolyte leakage was high from 10 dai onward in infected leaves. Net assimilation rate, stomatal conductance to water vapour, transpiration rate, internal CO₂ concentration, maximum quantum yield of photosystem (PS) II, and effective quantum yield of PS II significantly decreased as the disease developed. Quantum yield of regulated energy dissipation significantly increased at 10 and 15 dai but decreased at 20 dai whereas the quantum yield of non-regulated energy dissipation significantly increased at 15 and 20 dai. The content of Chl a, Chl b, and CAR decreased in infected leaves. The activities of the enzymes increased, and the relative expressions of the genes sod, cat 1, apx 2, pox, gr 1, and gst 23 were higher in infected leaves compared to non-infected ones mainly from 10 dai onward. In conclusion, photosynthesis in infected leaves was dramatically affected and a late involvement of the antioxidant metabolism was not sufficiently helpful to counteract the deleterious effects of fungal infection.

Keywords: carotenoids, gene expression, malondialdehyde, necrotrophic fungus, northern leaf blight, photosynthetic rate, stomatal conductance, transpiration rate.

Received: June 18, 2018; Revised: January 23, 2019; Accepted: January 24, 2019; Published online: October 22, 2019  Show citation