Effect of Nitrogen-fixing Bacteria on Germination, Seedling Vigour and Growth of Two Rice (Oryza sativa L.) Cultivars

To evaluate the effect of isolated nitrogen fixing plant growth-promoting bacteria (PGPB) on seed germination and growth promotion of rice cultivars (cv. BPT 5204 and Improved Samba Mahsuri). Eight promising N-fixing PGPB along with two standard cultures (viz. B. japonicum and G. diazotrophicus) were inoculated as seed treatment to rice genotypes and the effect on seed germination, seed vigour index and plant growth promotion of rice cultivars was assessed under in vitro (agar method) and in vivo (pot experiment) net house conditions. PGPBs (viz., Paenibacillus sonchi IIRRBNF1, Paenibacillus sp. IIRRNF2, Ochrobactrum sp. IIRRNF3, Burkholderia cepacia IIRRNF4, Burkholderia sp. IIRRNF5, Stenotrophomonas sp. IIRRNF6, Rhizobium sp. IIRRNF7 and Xanthomonas sacchari IIRRNF8) were enhanced seed germination, seed vigour index, seedling growth and dry matter accumulation (root and shoot dry matter) of rice cultivars under in vitro as well as in vivo conditions. Among all PGPB, Paenibacillus sonchi IIRRBNF1 exhibited the highest ability to stimulate plant growth promotion under both the conditions. The eight PGPB isolates exhibited positive influence on seed germination indices as well as growth promotion traits of rice cultivars at seedling stage and can be further evaluated at different growth stages under pot and field experiment.