Exogenous salicylic acid enhanced resistance of Foxtail Millet (Setaria italica) to Sclerospora graminicola

Abstract

To ward off pathogens, plants establish innate immunity system in which salicylic acid (SA) plays an important role. The downy mildew of foxtail millet (Setaria italica) is an oomycete disease caused by biotrophic pathogen Sclerospora graminicola, which seriously affects the yield and quality of foxtail millet. However, it is not clear how SA regulating the defense responses of foxtail millet. In this study, we found that spraying exogenous SA of low concentration (1 mM and 3 mM) had good effect on enhancing the resistance while high concentration (6 mM and 9 mM) did not significantly affect the defense of foxtail millet. Excess SA inhibited the growth and development of plants and we found spraying exogenous SA reduced the plant height, fresh weight and dry weight of foxtail millet. The low concentration of exogenous SA promoted the accumulation of Chlorophyll, soluble sugar and proline, promoted the activity of Phenylalanine Ammonia-Lyase and suppressed the accumulation of Malondialdehyde. After the treatment with 1 mM or 3 mM of SA, the expressions of genes related to disease resistance were increased at the early stage after treatment. The results indicated exogenous SA could enhance the resistance of foxtail millet against the pathogen and provided a basis for improving the control methods of downy mildew.