Abstract

Induced systemic resistance is an alternative mechanism to antagonism for achieving biological control of plant diseases. Induced Systemic Resistance (ISR) involves the activation of latent resistance mechanisms that are expressed upon subsequentsocalled “challenge’ inoculation with a pathogen. Induced resistance occurs naturally as a result of limited infection by the pathogen, particularly when the plant develops a hypersensitive reaction. Therefore, ISR as a mechanism of biocontrol against leaf blight disease (Helminthosporium turcicum) in maize, cv. CO 1 was investigated. The application effect of different formulations of Azospirillum and Paenibacillus cells viz., single strain inoculation, co-inoculation and co-aggregates (natural and artificial) on the enhancement of growth and reduction in leaf blight disease incidence of maize was studied under in vivo conditions. It was observed that the application of each formulation of Azospirillum and Paenibacillus cells augmented the growth parameters and reduction in the incidence of leaf blight disease of maize to a higher level when compared to un-inoculated control. However, the application of Azospirillum and Paenibacillus cells, as, natural co-aggregates, exhibited the highest performance followed by artificial co-aggregates of Azospirillum and Paenibacillus cells co-inoculation and single strain inoculation of PGPR cells. The comparative study of rhizobacterial EPS viz., Azospirillum and Paenibacillus and some ISR inducing chemicals viz., salicylic acid (SA), Jasmonic acid (JA) and Azibenzolar on the enhancement of growth and reduction in leaf blight disease incidence in maize plant revealed incidence to a higher level than rhizobacterial EPS but they couldn't augment the growth of the maize plant as in the case of rhizobacterial EPS. The application of rhizobacterial EPS had both phytostimulatory and biocontrol effect whereas the use of ISR inducing chemicals exert only biocontrol activity against Helminthosporium turcicum.