Changes in jasmonic and salicylic acids levels in barley challenged with cochliobolus sativus

Spot blotch (SB), caused by Cochliobolus sativus is a common foliar disease of barley worldwide. The phytohormones jasmonic acid (JA) and salicylic acid (SA) play important functions in plant defense systems. However, the changes in JA and SA pathways in response to SB disease have been poorly documented. In the current work and to better understand the mechanisms of barley resistance to this disease, JA and SA pathways were evaluated in resistant ‘Banteng’ and susceptible ‘WI2291’ cultivars across four time points post pathogen challenge. The data showed that JA and SA contents were elevated in fungus-inoculated and non-inoculated leaves in both resistant and susceptible interactions 24h post inoculation. However, although JA signaling was activated in parallel with SA signaling up to 72h in both cultivars, JA had no significant differences across four time points as compared with non-inoculated controls. Furthermore, the resistant cultivar ‘Banteng’ constitutively contained higher levels of SA (956.2 ng/g) comparing with the susceptible one ‘WI2291’ (192.5 ng/g) 96h post inoculation, whereas, JA pathway was weakly activated over time. We thus hypothesized that SA signaling has an important function in resistance mechanisms against SB disease, whereas JA signaling has a contrasting role in this defense system, which might prove crucial information concerning barley signaling events induced by C. sativus invasion.