Application of sodium salicylate up-regulates defense responseagainst Fusarium graminearum in wheat spikes

Abstract

Fusarium head blight caused by the hemibiotrophic fungus Fusarium graminearum is one of the most devastating diseases of wheat which reduces both grain yield and quality. To better understand mechanism underlying wheat resistance to this pathogen, the expressions of five candidate genes encoding phenylalanine ammonia-lyase (PAL), glucanase-2 (Gl 2), class IV chitinase (Cht-4), cytochrome P450 (CYP), and pleiotropic drug resistance (PDR) following spike inoculation with F. graminearum was compared in susceptible cv. Falat and resistant cv. Sumai3 at three time points (48, 96, 144 h after inoculation). Real-time quantitative PCR analysis indicated earlier and greater inductions of PAL, Glu-2, and Cht-4 in spikes of 'Sumai3' as compared to 'Falat' in response to F. graminearum inoculation. The expression of CYP in the resistant 'Sumai3' was about three times higher than in 'Falat' at 144 h after pathogen inoculation. Moreover, soil drench application of sodium salicylate (SA) one day before pathogen inoculation drastically curtailed pathogen infection in both the cultivars. Furthermore, SA treatment caused an induction of these genes in spikes of the susceptible cultivar to show a similar pattern as in the resistant one when inoculated with F. graminearum. Proteomics analysis of F. graminearum treated spikes 96 h after inoculation confirmed an increase of Glu and Cht spot volume in 'Sumai3' whereas a decrease in 'Falat'. The SA treatment also caused significant increases in Glu and Cht spot volumes in both the cultivars. Our findings show an association between SA improvement of wheat defense against F. graminearum infection and induction of genes encoding proteins involved in pathogen response (Glu-2, Cht-4), secondary metabolite biosyntheses (PAL), and xenobiotic detoxification (CYP and PDR).