Modulation of germination physiology and biochemical metabolism in rice (Oryza sativa L.) through microbial seed biopriming
Seed biopriming is an eco-friendly technique that enhances seed germination and seedling growth through the application of beneficial microorganisms. The study evaluated the effects of seed biopriming with four plant growth-promoting rhizobacteria (PGPR) such as Azospirillum lipoferum, Bacillus megaterium, Paenibacillus mucilaginosus and Pseudomonas chlororaphis at concentrations of (10–40 %) on seed quality traits of rice cultivars CO 53 and TKM 15, compared with hydroprimed and untreated seeds. The results revealed that biopriming with 20 % A. lipoferum significantly improved seed quality parameters in both varieties. In CO 53, the 20 % A. lipoferum recorded the highest germination percentage (90 %), total seedling length (33.0 cm), vigour index (2970) and dry matter production (0.135 g seedling-1) compared to the untreated control. Bioprimed seeds also exhibited enhanced α-amylase activity (1.630 mg maltose min-1 g-1), reducing sugar content (2.56 mg g-1) and dehydrogenase activity (0.47), along with a reduction in starch content (7.6 mg g-1), indicating efficient mobilisation of seed reserves during germination. Similar trends were observed in TKM 15, where 20 % A. lipoferum significantly enhanced both physiological and biochemical seed parameters. The enhanced performance of bioprimed seeds was attributed to microbial stimulation of enzymatic activities, improved nutrient availability and increased production of growth-promoting metabolites, which collectively promoted rapid germination and vigorous seedling growth. The findings demonstrate that seed biopriming with A. lipoferum is an effective and sustainable strategy for improving seed vigour and physiological performance in paddy. Seed biopriming with beneficial rhizobacteria represents a promising strategy for improving seed quality and supporting sustainable rice cultivation.