The effectiveness of rhizosphere bacteria in inducing the resistance of maize to downy mildew, Peronosclerospora philipinensis

The aim of study was to determine the efficacy of bacterial isolates from the rhizosphere in influencing the resistance of maize to downy mildew by measuring the accumulated concentration of salicylic acid. Treatments were based on a fully randomized 2- factor design with 3 levels of; factor I (bacteria) 3 levels (b0 = no bacteria, b1 = Bacillus paramycoides Ga-3, b2 = B. cereus Si-4) and factor II (salicylic acid) 2 levels (as0 = 0 g/L and as1 = 2 g/L). The research was carried out at the greenhouse and plant pathology laboratory, Indonesian Cereal Research Institute (ICERI), from March to July 2020. Each treatment combination was tested on three varieties of maize, namely Anoman, Bima20, and Bima3. Hence there were 18 treatment combinations. Furthermore, the results showed that rhizosphere bacteria and salicylic acid could control downy mildew in maize. In the case of the Bima20 variety, the combined treatment of B. paramycoides Ga3 + salicylic acid had the lowest incidence of disease at 13%. Meanwhile, treatment of B. cereus Si4 + salicylic acid in the Bima3 variety had the lowest incidence of disease by 26%. Considering the results, the enrichment of salicylic acid content was highest at 9.6 ppm on maize which was applied with the rhizosphere bacterium B. paramycoides Ga3 + salicylic acid.