Reduction of the severity of Asian soybean rust with foliar application of silicon dioxide

Abstract

Asian soybean rust (Phakopsora pachyrhizi; ASR) is one of the main diseases that affect soybeans, and it is controlled mainly with chemical fungicides. Induction of plant defense with silicon dioxide (SiO2) application could also be considered to control the disease. However, there is no information on the use of SiO2 as a source of silicon to control ASR. Silicon is an element related to the induction of plant defense mechanisms. Thus, the aim of this study was to verify the in vitro effect of SiO2 on the germination of uredospores of P. pachyrhizi and whether foliar application reduces ASR severity. The in vitro experiment was conducted with six treatments (0; 0.1; 1; 10; 100; 1000 μg.L−1 of SiO2) while the in vivo experiment was carried out with four treatments (0; 1; 2.5; 5% SiO2) under controlled conditions. There was no effect of SiO2 on the germination of uredospores of P. pachyrhizi, yet there was a reduction of up to 85% in the number of uredia with application of 4% SiO2. Plants that received 5% of SiO2 accumulated about 60% more silicon in their leaf tissues compared to the control treatment, increasing 22.99 mg kg−1 of silicon for each percentage point of SiO2 applied. Thus, our study demonstrates that foliar application of SiO2 reduces the severity of ASR and provides greater accumulation of silicon in soybean leaf tissues.