Changes in salicylic acid content and pathogenesis - related (PR2) gene expression during barley - Pyrenophora teres interaction

Net blotch (NB), caused by the necrotrophic fungal pathogen Pyrenophora teres f. teres, substantially reduces barley grain yield and quality worldwide. The role of salicylic acid (SA) signaling in NB resistance has been poorly documented. In this study, SA levels as well as the expression of the SA-responsive gene PR2 were monitored in infected leaves of two barley genotypes, Banteng (resistant) and WI2291 (susceptible), at different time points of infection. SA signaling was activated in bothgenotypes 24 hours post infection (hpi) as compared with non-inoculated plants. However, with or without pathogen pretreatment, SA signifi cantly increased (P=0.001) in Banteng comparing with WI2291. RT-PCR analysis revealed that PR2 expression increases in the resistant and susceptible genotypes over the inoculation time points, with maximum expression (6.4 and 1.99-fold, respectively) observed 6 dpi. PR2 expression was paralleled by an increase in leaf SA content as shown by the test coincidence (F₃, ₃₂ = 4.74, P = 0.001). Based on barley genotype resistance levels, our data strengthen the idea that SA signaling and PR2 play a role in barley NB reduction