Development of non-sterile inorganic carrier-based formulations of fluorescent pseudomonad R62 and R81 and evaluation of their efficacy on agricultural crops

Talc and aluminum silicate powders were used to develop inorganic carrier-based formulations of fluorescent pseudomonad strains R62 and R81. The aerobically cultivated cell-free broth of both the strains contained a hydroxamate-type siderophore and an antibiotic 2,4-diacetylphloroglucinol (DAPG). The formulations of these bioinoculants were able to bring the natural contaminants in the non-sterile carriers to acceptable limits in the presence of 54.6 μg g−1 of siderophore and 10 μg g−1 of DAPG. The shelf life of talc powder-based formulation was about 1 year in comparison to about 100 days for aluminum silicate-based formulation. Both sterile and non-sterile carrier formulations worked significantly well in comparison to their controls for growth of Vigna mungo and Triticum aestivum crops. Sterile talc powder-based formulation of strain R81 showed maximum increase in dry root weight, dry shoot weight, and root volume of Vigna mungo over that with aluminum silicate-based formulation. On Triticum aestivum, the growth response was better in the case of R62-treated seeds in comparison to treatment with R81. However, a consortium of talc powder formulation of R62 and R81 gave the best increase of 46% for sterile and non-sterile carriers in grain yield of Triticum aestivum over respective controls.

Research highlights▶ Siderophore and DAPG improved efficacy of non-sterile bioinoculant formulations. ▶ Viability of the pseudomonads in talc-based formulations was retained for a year. ▶ The pseudomonads improved growth of Vigna mungo and Triticum aestivum crops.