Inducers of resistance and silicon on the activity of defense enzymes in the soybean-Phakopsora pachyrhizi interaction

Abstract

This study aimed to determine the effect of jasmonic acid (JA), Acibenzolar-S-Methyl (ASM) and calcium silicate (a source of soluble silicon, Si), on the potentiation of soybean resistance to Asian soybean rust (ASR). The ASR severity was significantly reduced on plants sprayed with ASM or supplied with Si in comparison to plants sprayed with JA or deionized water. For chitinases (CHI), significant differences in activity between non-inoculated and inoculated plants sprayed with deionized water or with ASM occurred at 72 hours after inoculation (hai), at 24 and 72 hai when sprayed with JA and at 141 hai when supplied with Si. For β-1,3-glucanases (GLU), significant differences in activity between non-inoculated and inoculated plants sprayed with deionized water occurred at 24, 48 and 141 hai, but not until 72 for plants sprayed with ASM. For phenylalanine ammonia-lyases (PAL), significant differences in activity between non-inoculated and inoculated plants occurred only for plants sprayed with ASM at 72 and 141 hai. In conclusion, the ASR symptoms can be mild on plants sprayed with ASM or supplied with Si and that this amelioration likely involved the defense enzymes.Key words: Glycine max, Asian soybean rust, induction of resistance, mechanisms of host defense.Indutores de resistência e silício na atividade de enzimas de defesa na interação soja-Phakopsora pachyrhizi ResumoEste estudo objetivou determinar o efeito do ácido jasmônico (AJ), do Acibenzolar-S-Metil (ASM) e do silicato de cálcio (fonte de silício solúvel, Si) na potencialização da resistência da soja à ferrugem asiática (FA). A severidade da FA foi significativamente reduzida nas plantas pulverizadas com ASM ou supridas com Si em comparação com as plantas pulverizadas com água deionizada ou AJ. Para a atividade das quitinases (QUI), diferenças significativas entre plantas não inoculadas e inoculadas que foram pulverizadas com água destilada ou ASM ocorreram às 72 horas após a inoculação (hai); às 24 e 72 hai para plantas pulverizadas com AJ e às 141 hai quando supridas com Si. Para β-1,3-glucanases (GLU), diferenças significativas entre plantas inoculadas e não inoculadas que foram pulverizadas com água deionizada ocorreram às 24, 48 e 141 hai, mas não ocorreram até as 72 hai para plantas pulverizadas com ASM. Para fenilalanina amônia-liases (PAL), houve diferença significativa na atividade entre plantas inoculadas e não inoculadas somente para aquelas pulverizadas com ASM as 72 e 141 hai. Em conclusão, os sintomas da FA podem ser reduzidos em plantas pulverizadas com ASM ou em plantas supridas com Si, em parte, pela participação das enzimas de defesa estudadas.Palavras-chave: Glycine max, ferrugem asiática, indução de resistência, mecanismos de defesa do hospedeiro.

Leaf gas exchange and chlorophyll a fluorescence in soybean leaves infected by Phakopsora pachyrhizi

“…Moreover, photosynthesis was preserved at the photosynthetic machinery level coupled with lower destruction of photosynthetic pigments and greater leaf gas exchange capacity of the infected plants. It is known that both Epo+Pyr and ASM can decrease ASR severity as well as the number of pustules per leaf (Cruz et al., ; Duarte et al., ; Miles et al., ; Rodrigues et al., ). The QoI fungicides affect both spore germination and fungal penetration into the host′s tissues and these are both detrimental against fungal infection (Bartlett et al., ).…”

“…According to Cruz et al. (), the reduction in ASR severity on soybean plants sprayed with ASM was linked with an increase in chitinases and phenylalanine ammonia‐lyases activities.…”

“…Moreover, photosynthesis was preserved at the photosynthetic machinery level coupled with lower destruction of photosynthetic pigments and greater leaf gas exchange capacity of the infected plants. It is known that both Epo+Pyr and ASM can decrease ASR severity as well as the number of pustules per leaf (Cruz et al, 2013;Duarte et al, 2009;Miles et al, 2007;Rodrigues et al, 2009).…”

“…On the other hand, the DMI fungicides affect the growth of fungal hyphae on host′s tissues (Kuck, Stenzel, & Vors, 2012). According to Cruz et al (2013), the reduction in ASR severity on soybean plants sprayed with ASM was linked with an increase in chitinases and phenylalanine ammonia-lyases activities.…”

“…Application of foliar fungicides, particularly quinone outside and demethylation inhibitors (QoIs and DMIs), has been recommended for minimizing the losses caused by ASR (Langenbach, Campe, Beyer, Mueller, & Conrath, 2016). Additionally, the use of inducers of resistance such as the Acibenzolar-S-Methyl (ASM), an analogue of the salicylic acid, could be an alternative for ASR management (Cruz, Rodrigues, Diniz, Moreira, & Barros, 2014;Cruz et al, 2013;Dallagnol, Navarini, Ugalde, Balardin, & Catellam, 2006;Duarte, Zambolim, Rodrigues, Rios, & Lopes, 2009;Rodrigues et al, 2009).…”