Article

The present study explores the plant growth-promoting traits of Fusarium soil isolate and also their estimation under various conditions of metal stress. Fusarium sp. was isolated from an agriculturally important soil of Murshidabad district in West Bengal, India by serial dilution plate technique on selective medium using pentachloronitrobenzene and was later identified by spore morphology and molecular study. The Fusarium sp was found to be non-pathogenic soil isolate based on increased germination percentages and vigour index values of six seed plants viz., chickpea, black gram, cucumber, chilli, mustar and paddy . The fungal isolate produced substantial amount of IAA in tryptophan-supplemented broth (370 µg/ml) and also produced GA in colossal amounts (4800 µg/ml). The Fusarium sp. could resist the tested heavy metals viz., Cd, Cu, Fe, Ni and Zn and MIC values were in the range from as low as 175 ppm (Cd) to as high as 350 ppm (Fe). The isolate produced IAA and GA in metal-contaminated broths. But, Cd at 50 ppm concentration completely inhibited both IAA and GA production. Zn at 50 ppm concentration was also found to be inhibitory to the isolate with regard to its ability to produce IAA. But GA production continued uninhibited (3500-4250 µg/ml) in the presence of the tested heavy metals at minimum (50 ppm) concentrations. Siderophore production by the isolate was found to be on the higher range (400-540 nmole/ml) in presence of Cu, Fe and Zn. Phosphate solubilisation remained unaffected (1400-1800 ppm) by the Fusarium isolate in presence of the tested heavy metals except Cd. Thus, the soil isolate could be of immense use in metal-contaminated agricultural soils to increase yields of agronomically important crops.