Azoxystrobin induces lignification-related enzymes and phenolics in rice (Oryza sativaL.) against blast pathogen (Pyricularia grisea)

Abstract

This study was conducted to analyse the induction of lignification-related enzymes and phenolic content in rice to blast disease caused by Pyricularia grisea using azoxystrobin. The severity of rice blast was reduced (70% over control) through treatment by azoxystrobin. This reduction in disease severity was mainly associated with induction of host defense mechanisms by azoxystrobin. Increased production of secondary metabolite Á phenolic and lignification Á related enzymes, namely, peroxidase (POD), polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL) were observed in rice plants treated with azoxystrobin.

Rice defense responses to Bipolaris oryzae mediated by a strobilurin fungicide

“…At advanced stages of fungal infection (144 hai), however, the high concentration of TSP appeared to play a pivotal role in limiting fungal invasion in the leaf tissue of azoxystrobin-sprayed plants in contrast to their -Fu counterparts. Consistent with our findings, rice plants treated with azoxystrobin and inoculated with P. oryzae accumulated high concentration of TSP than did the non-treated plants (Sundravadana et al 2007). Many preformed phenolic compounds such as chlorogenic, p-coumaric, ferulic, salicylic, cinnamic and caffeic acids are known to occur in rice (Kuwatsuka and Oshima 1962;Varga 1970) which can become associated to lipids and phospholipids, thereby increasing membrane permeability, electrolyte leakage and cytoplasm aggregation in the fungal cells (Southerton and Deverall 1990;Xiao et al 1991).…”

“…Irrespective of the fungicide treatment, inoculated plants displayed higher activities of PAL, POX and PPO than their non-inoculated counterparts, indicating that such enzymes are integral part of the basal rice resistance against brown spot. Accordingly, rice plants infected with B. oryzae or P. oryzae showed increases in the activities of such enzymes or in the levels of their transcripts either in compatible or incompatible interactions (Rodrigues et al 2005;Sundravadana et al 2007;Dallagnol et al 2011). However, the activities of POX and PPO were transiently increased by azoxystrobin spray in the present study.…”

“…Similarly to what was found in the present study, some authors have suggested that strobilurin fungicides prime plants for enhanced defense against pathogens infection, fact that was supported by earlier and higher accumulation of PR1 transcripts in pyraclostrobin-treated plants, which was associated with tobacco resistance to Pseudomonas syringae pv. tabaci and TMV (Herms et al 2002) as well as by higher activities of PAL, POX and PPO observed in azoxystrobin-treated plants that was linked to rice resistance to blast (Sundravadana et al 2007).…”

“…In addition to their fungicidal activity, there are compelling evidences that strobilurins can reprogram plant metabolism, benefiting growth and enhancing defense against abiotic and biotic stress (Conrath et al 2015). Regarding strobilurinmediated plant defense responses to pathogen attack, it was showed that pyraclostrobin primed tobacco plants for accelerated PR1 induction after Tobacco mosaic virus (TMV) infection (Herms et al 2002), whereas azoxystrobin was found to enhance the production of secondary metabolites (phenolics and lignin) and enzymes activities (POX, PPO and PAL) in rice plants infected with P. oryzae (Sundravadana et al 2007).…”

The mononuclear nickel(II) complex bis(azido-κN)bis[2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole-κ2N2,N3]nickel(II) protects tomato fromVerticillium dahliaeby inhibiting fungal growth and activating plant defences

“…Probenazole controls rice blast by both inhibiting the growth of Pyricularia grisea and stimulating the plant defence mechanisms. The main mode of action of fungicide azoxystrobin is to inhibit mitochondrial respiration of the pathogen and induce the activity of enzymes involved in lignification, such as PAL, POX and PPO . Enhancement of POX and PPO activities results in the reinforcement of cell walls by lignification, which acts as a physical barrier preventing or reducing pathogen colonisation .…”