Co-inoculant Response of Microbial Consortia on Physiology of Blackgram [Vigna mungo (L.) Hepper] Seed Germination

Background: Blackgram (Vigna mungo (L.) Hepper) belonging to the Leguminoceae family is rich in protein. In this crop, biological seed treatment is an environmentally sound approach for improving the vigour of seeds. Besides legume-Rhizobium symbiosis, several other beneficial microbes play a crucial role in vigour enhancement in blackgram. Methods: The surface sterilised seeds were first coated with 20% gum acacia followed by the coating with bioinoculants viz., T0 - Control (Dry seed), T1 - Rhizobium sp. BMBS + Arbuscular Mycorrhizal Fungi (AMF) + Methylobacterium extorquens AM1 and T2 - Rhizobium sp. BMBS + AMF + Bacillus velezensis. Result: Inoculation of blackgram seeds with the Rhizobium sp. BMBS and AMF with Methylobacterium extorquens AM1 resulted in a significant increase in germination (97%), dry matter production (0.237 g 10 seedlings-1), vigour index (22.99) and seed mobilization efficiency (1.11) as compared to control seeds. The biochemical parameters such as á-amylase and proteases were found to be significantly higher in the Rhizobium sp. BMBS + AMF + Methylobacterium extorquens AM1 inoculated seeds. Changes in root exudates composition due to co-inoculation assessed through GC-MS, indicated compounds with antioxidant and antimicrobial activities. Our results confirmed that the positive interaction of rhizobial strain BMBS and AMF with Methylobacterium extorquens AM1 may emerge as a novel bio-inoculant for sustainable pulse productivity.