Biochemical defense in maize against Chilo partellus (Swinhoe) through activation of enzymatic and nonenzymatic antioxidants

Abstract

Biochemical defense against herbivores is one of the most important components of plant resistance to insects. Here, we studied the constitutive and induced biochemical defense through activation of enzymatic and nonenzymatic antioxidants in response to damage by the spotted stem borer, Chilo partellus (Swinhoe) in six maize genotypes including resistance and susceptible checks. The levels of total sugars, total soluble protein and starch were significantly lower, while total phenol and total antioxidant higher in resistant than susceptible maize genotypes both under damaged and healthy plant conditions. The activity of antioxidant enzymes like AO, CAT, APX, PAL and TAL were significantly higher in resistant than susceptible genotype, Basi Local, which further increased in response to damage by C. partellus. The nonenzymatic antioxidant scavenging activity of FRAP was also significantly higher in resistant maize genotypes, which further increased upon damage by C. partellus. Total antioxidant activity increased from 22.2 to 96.3% across test maize genotypes in response to damage by C. partellus, wherein maximum increase was recorded in CML 345. These findings clearly demonstrate that both constitutive and induced biochemical compounds through activation of enzymatic and nonenzymatic antioxidant defense systems impart resistance against C. partellus in CPM 8, CPM 13, CPM 15, CPM 18 and CML 345, thus could be used in insect resistance breeding program. These studies could also be useful for detailed understanding on metabolic pathways regulating biochemical defense and up- and down-regulation of associated genes in plant defense against biotic stresses.