Enzymes of Phenylpropanoid Metabolism Involved in Strengthening the Structural Barrier for Providing Genotype and Stage Dependent Resistance to Karnal Bunt in Wheat

Abstract

The role of lignifications and enzymes involved in the phenylpropanoid (PP) biosynthesis i.e. phenylalanine ammonia lyase (PAL), Peroxidase (POD), Polyphenol oxidase (PPO) in providing resistance to Karnal Bunt (KB) during different developmental stages of resistant (HD-29) and susceptible genotype (WH-542) and its recombinant inbred lines (RILs) of wheat were investigated. The enzymes of PP pathway were expressed constitutively in both the susceptible and resistant genotype. However, the activity was higher in all the developmental stages of resistant genotype and its RILs, indicating that this genotype has a significant higher basal level of these enzymes as compared to the susceptible line and could be used as marker(s) to define KB resistance. The activity of PAL and POD was significantly higher in WSv stage (Z = 16) while the specific activity of PPO was higher in WS3 (Z = 77) stage as compared to the other physiological stages in both the genotypes. In resistant genotype the lignin content increased two-fold and three-fold at WS2 and WS3 stage, respectively, while in susceptible genotype no significant increase in lignin content was observed. The pathway might be associated with the enhancement of structural defense barrier due to lignifications of cell wall as evident from the enhanced synthesis of lignin in all the stages of resistant genotype. Our results clearly indicate the possible role of enzymes of PP metabolism provides genotype and stage dependant structural barrier resistance in wheat against KB.