Silício na indução de resistência a Sitobion avenae (Fabricius, 1775) (Hemiptera: Aphididae), na produtividade e na produção de voláteis em plantas de trigo

Abstract

Wheat (Triticum aestivum L.) is the most widely cultivated crop worldwide. Despite being a known responsive grass to fertilization with silicon (Si), there are few studies in the field with the crop to confirm its effect on grain yield, in the induction of resistance to aphids and production of plant volatiles. In order to evaluate these characteristics four trials were conducted, three in the field and one in the laboratory. The first and the second field tests (2012 and 2014) were done to evaluate the production characteristics and resistance induction promoted by Si against aphids in wheat cultivars. The first test was conducted in the experimental area of EPAMIG in Uberlândia, Minas Gerais, in a randomized block design, with three repetitions and a 3x2x5 factorial (wheat cultivars: BRS 254, BRS 264 and BRS Timbaúva, fertilized or not with Si at 300 kg ha , and evaluated at 90, 97, 104, 111, 118 days after sowing). The second test was conducted at Fazenda Capim Branco in Uberlândia, Minas Gerais, in a randomized block design with four replications and split plot scheme in time (four Si levels: 50, 100, 150 and 200 kg ha and a control distributed in plots, two wheat cultivars - BRS 254 and BRS Timbaúva - in the subplots, and the evaluation of aphid population in time as subsubplots). The third trial was done in 2015, evaluating the stability of Si induced resistance to Sitobion avenae and productivity of BRS 254 in two sowing dates (April and May). The experiment was conducted at Fazenda Capim Branco with four Si levels in a randomized block design with four replications. The fourth trial was conducted in 2015 in the laboratory of ESALQ Insect Behavior, in Piracicaba, São Paulo. BRS 254 wheat plants were subjected to Si fertilization and, or, to herbivory by Rhopalosiphum padi, and a control without herbivory and without Si. Field results showed that Si induced resistance against the aphid S. avenae, and this induction was enhanced by increasing Si doses, especially at wheat reproductive stage. It was also observed that the induction of resistance was stable over two wheat growing seasons, even in different densities of S. avenae. Wheat cultivars BRS 254 and BRS 264 were more susceptible to aphids than Timbaúva; however, fertilization with Si induced resistance and increased productivity in all tested cultivars. In the absence of Si fertilization, BRS Timbaúva showed lower population density of aphids in all tests. In the laboratory test, it was observed that Si, with or without herbivory, stimulated the production of volatile organic compounds by wheat plants.