Plant growth promoting activities of phosphate- solubilizing Enterobacter asburiae as influenced by fungicides

Four fungicides, tebuconazole, hexaconazole, metalaxyl and kitazin were applied at recommended and higher rates to examine their effects on the plant growth promoting activities of the fungicide tolerant Enterobacter asburiae strain PS2 under in vitro conditions. Enterobacter asburiae strain PS2 was isolated from the mustard rhizosphere and was assessed for the fungicide-tolerance and production of plant growth promoting traits (phosphate solubilization, siderophores, indole acetic acid, exo-polysaccharides, hydrogen cyanide and ammonia production) both in the presence and absence of fungicides. Enterobacter asburiae strain PS2 showed plant growth promoting activities even in the presence of fungicides which however, decreased progressively with the increase in fungicide concentration. Fungicides at recommended dose had little effect while the dose higher than the recommended one adversely affected the physiological traits, like, phosphate solubilization, siderophore, and indole acetic acid synthesis. Among all fungicides, tebuconazole in general, showed maximum toxicity to plant growth promoting activities. Fungicide-tolerant E. asburiae strain PS2 with the inherent ability to produce growth regulators even in the presence of fungicides can be exploited as a bio-inoculant to increase the productivity of crops grown in fungicide stressed soils.