SHORT COMMUNICATION Silicon-mediated maize resistance to macrospora leaf spot Caroline Hawerroth 1 & Leonardo Araujo 2 & Maria B. Bermúdez-Cardona 3 & Patrícia R. Silveira 1 & João A. Wordell Filho 4 & Fabrício A. Rodrigues 1 Received: 14 March 2018 /Accepted: 31 July 2018 # Sociedade Brasileira de Fitopatologia 2018 Abstract This study investigated the effect of silicon (Si) on maize resistance against macrospora leaf spot (MLS) caused by the fungus Stenocarpella macrospora. Maize plants susceptible to MLS were grown in a Si-deficient soilless potting mix and irrigated daily with either potassium silicate solution or potassium chloride solution. The amount of potassium was equilibrated between the solutions. The severity of MLS was evaluated at 48, 72, 96, 120 and 168 h after inoculation and data were used to calculate the area under MLS progress curve (AUMLSPC). The foliar Si concentration in Si-supplied plants (2.8 dag/kg) significantly increased in comparison to non-supplied ones (0.6 dag/kg). The AUMLSPC was significantly reduced by 42% in Si-supplied plants (368.3) when compared with non-supplied ones (635.0). Fungal hyphae grew abundantly in the leaf tissue of non-supplied in comparison to Si-supplied plants based on light and scanning electron microscopy observations. Cell walls in the leaf tissue of Si-supplied plants were rarely degraded, and fungal hyphae were surrounded by phenolic compounds. In conclusion, marked differences in the infection process of S. macrospora were noticed between Si-supplied and non-supplied plants. The role of Si acting as a physical barrier and potentiating the phenylpropanoid pathway in maize was of great importance for resistance to MLS. Keywords Stenocarpella macrospora . Host defense response . Phenolics . Plant nutrition . Phenylpropanoid pathway Maize (Zea mays L.) production can be negatively impaired by the occurrence of macrospora leaf spot (MLS), caused by Stenocarpella macrospora (Earle) Sutton (syn. Diplodia macrospora Earle), especially when grown in the humid sub- tropical and tropical regions worldwide (Latterell and Rossi 1983. On leaves, MLS symptoms appear as small brown spots of water-soaked appearance with a chlorotic halo (Casa et al. 2006). As the lesions expand, they become irregular or elliptical and develop concentric rings with a reddish or yellow halo Casa et al. 2006, Bradley et al. 2010). In the necrotic leaf tissues, subepidermal, globose or elongated pycnidia of dark brown color are abundantly produced (Bradley et al. 2010; Bermudez-Cardona et al. 2016). Conidia are often released from cirri on pycnidia and spread by wind and rain under warm and moist conditions (Casa et al. 2004). Considering fungal mycelia and pycnidia on maize debris as the main source of primary inoculum for MLS epidemics, plant residue management, crop rotation and the use of healthy seeds are of detrimental importance for MLS control (Casa et al. 2003, 2006; Bampi et al. 2012). There is no fungicide registered for MLS control, and resistant commercial hybrids are not available (Bampi et al. 2012; Piletti et al. 2014). New control strategies for MLS management are urgently needed to reduce the yield losses caused by this disease. The supply of silicon (Si) to crops of economic importance, such as maize, shows promise as an environmentally friendly choice considering the potential of this quase-essential ele- ment to decrease the intensities of several roots and foliar diseases (Rodrigues et al. 2015; Debona et al. 2017). Symptom reduction of foliar diseases affecting several mono- cots is linked to the effect of Si on some components of host resistance, such as incubation period, latent period, lesion size, Section Editor: Marcelo A. Carmona * Fabrício A. Rodrigues fabricio@ufv.br 1 Departamento de Fitopatologia, Universidade Federal de Viçosa, Viçosa, Minas Gerais CEP 36570-900, Brazil 2 Laboratorio de Fitopatología, Universidad del Tolima, Tolima, Colombia 3 Laboratório de Fitopatologia, EPAGRI, São Joaquim, Santa Catarina CEP 86600-000, Brazil 4 Laboratório de Fitossanidade, EPAGRI/CEPAF, Chapecó, Santa Catarina CEP 89801-970, Brazil Tropical Plant Pathology https://doi.org/10.1007/s40858-018-0247-8