Not AvailableBackground: Castor (Ricinus communis L.) is cultivated for seed oil and to feed (leaves) Eri silkworm, Samia ricini
(Donovan) Hutt. Alternaria blight affects castor cultivation resulting substantial yield loss (~30%). Uses of synthetic fertilizers and agrochemicals for disease management have serious concerns as the castor leaves are fed to
eri silkworms for rearing. Application of plant growth promoting rhizobacteria for disease suppression and to
enhance plant growth will be a healthier choice in castor cultivation. The aim of this study was to assess the
efficacy of Alternaria blight disease suppression by native rhizobacteria isolated from wasteland castor and their
ability on plant growth promotion.
Methodology: We isolated 50 bacterial antagonists from castor rhizosphere using the dilution plate method and
evaluated their antagonistic activity against the castor blight pathogen, Alternaria ricini. Based on antimicrobial
bioassay and plant growth promotion (PGP) traits (phosphate solubilization, ACC deaminase activities, production of IAA, GA3, HCN, NH3 and siderophore), salt and acid tolerance; we have chosen ten potential isolates and
identified them through 16SrRNA gene sequencing and analysis. Disease suppression and plant growth studies
were evaluated in pot experiments.
Results and conclusion: Three isolates namely, Enterobacter hormaechei (LRP-2), Bacillus mycoides (HF-1) and
B. aryabhattai (UR-6) showed potential antagonistic activities and PGP traits which were selected for disease
suppression and PGP studies. Application of PGPR consortia (LRP-2þHF-1) could suppress the plants from A. ricini
infection in challenged inoculation. Mix inoculation of LRP-2 and UR-6 showed synergistic effect and enhanced
plant growth in pot experiments. Combinations of E. hormaechei (LRP-2), B. mycoides (HF-1) and B. aryabhattai
(UR-6) can be applied as bio-control and bio-fertilizer formulation to protect castor from Alternaria blight and also
to enhance plant growth.Not Availabl