Abstract
Bipolaris maydis and Exserohilum turcicum are important fungal pathogens that cause leaf blight in corn whose control have been difficult. Essential oils are a promising and environmentally friendly alternative for disease management, but the mechanisms of action remain poorly studied. Here, we aimed to assess the effect of B. maydis and E. turcicum as well as the essential oil of Morinda citrifolia in the activity of plant defense enzymes in corn plants. Experiments were carried out in a completely randomized design with three replications and six treatments as they follow: (T1): corn plants inoculated with B. maydis; (T2): corn plants inoculated with E. turcicum; (T3): corn plants treated with essential oil of M. citrifolia (0.25%) and inoculated with B. maydis; (T4): corn plants treated with essential oil of M. citrifolia (0.25%) and inoculated with E. turcicum; (T5): corn plants treated with essential oil of M. citrifolia (0.25%); and (T6): corn plants non-inoculated and treated with distilled water. Protein content (PC) and activities of the enzymes ascorbate peroxidase, catalase, chitinase (CHI), peroxidase (POX) and superoxide dismutase (SOD) were assessed. PC was significantly decreased, whereas CHI and SOD activity was higher in T1-T5 compared to T6. T4 and T5 significantly increased POX activity relative to T6. Therefore, our findings suggest that the essential oil of M. citrifolia may play an active role in disease control by activating defense enzymes in corn plants.
Highlights
Corn (Zea mays L.) is one of the most important cereals for human and animal consumption and it is grown for grain and forage
Experiments were carried out in a completely randomized design with three replicates and six treatments as they follow: (T1): corn plants inoculated with Bipolaris maydis; (T2): corn plants inoculated with Exserohilum turcicum; (T3): corn plants sprayed with essential oil of M. citrifolia (0.25%) and inoculated with B. maydis; (T4): corn plants sprayed with essential oil of M. citrifolia (0.25%) and inoculated with E. turcicum; (T5): corn plants sprayed with essential oil of M. citrifolia (0.25%); (T6): corn plants sprayed with distilled water
We provide novel evidences at the biochemical level of the effect of B. maydis and E. turcicum as well as the essential oil of M. citrifolia in corn leaves and shed light on the potential indirect effect of the essential oil in southern leaf blight (SLB) and northern leaf blight (NLB) control
Summary
Corn (Zea mays L.) is one of the most important cereals for human and animal consumption and it is grown for grain and forage. Corn ranks first in production, accounting for 1,052 million metric tons in the world. Brazil is the third largest producer with 9% of the world production, after USA (34%) and China (21%) (USDA, 2018). Notably southern leaf blight (SLB) and northern leaf blight (NLB), caused by Bipolaris maydis (teleomorph: Cochliobolus heterostrophus) and Exserohilum turcicum (teleomorph: Setosphaeria turcica), respectively, are known to affect corn production worldwide. SLB is considered to be the most important and wide spread corn leaf disease around the world and it is prevalent in warm humid temperate to tropical regions, where temperatures ranges from 20-30 °C during cropping period (Singh & Srivastava, 2012). Different strategies, including cultural practices, genetic resistance and fungicide application can be employed in SLB and NLB management. Broad-spectrum fungicides, including propiconazole, fluazinam, benzovindiflupyr, chlorotalonil and mancozebe were demonstrated to be effective, but pathogen sensitivity to some of them has been shown to jas.ccsenet.org
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