Potential of Pseudomonas putida, Bacillus subtilis, and their mixture on the management of Meloidogyne incognita, Pectobacterium betavasculorum, and Rhizoctonia solani disease complex of beetroot (Beta vulgaris L.)

Effects of Pseudomonas putida and Bacillus subtilis alone, and in combinations for the management of Meloidogyne incognita , Pectobacterium betavasculorum , and Rhizoctonia solani disease complex of beetroot ( Beta vulgaris L.), were studied. Application of P. putida or B. subtilis to plants with M. incognita or P. betavasculorum or R. solani singly or in combinations caused a significant increase in plant growth parameters and the activities of defense enzymes. A significant increase in chlorophyll fluorescence attributes, viz., Fv/Fm, ɸPSII, qP, NPQ, and ETR were recorded in plants treated with P. putida or B. subtilis over pathogen-inoculated plants. Inoculation of P. putida results in a higher reduction in galling and nematode multiplication than B. subtilis . Maximum reduction in nematode multiplication and galling occurred when a mixture of P. putida and B. subtilis was used. Soft rot and root rot indices were 3 when Pectobacterium betavasculorum and Rhizoctonia solani were inoculated alone. The disease indices were rated 5 when these pathogens and M. incognita were inoculated in combinations. Inoculation of P. putida / B. subtilis with P. betavasculorum or R. solani reduced soft rot and root rot indices to 2 out of 3, while the use of P. putida + B. subtilis reduced indices to 1. Disease indices were reduced to 2–3 out of 5, when P. putida + B. subtilis were used to plants inoculated with two or three pathogens. The principal component analysis showed significant correlations among the various studied attributes. Two principal components explained a total of 86.1 and 93.4% of the overall data variability. Therefore, the use of P. putida together with B. subtilis had the potential for successful management of disease complex of beetroot.