Harnessing the phosphate-solubilizing ability of Trichoderma strains to improve plant growth, phosphorus uptake and photosynthetic pigment contents in common bean (Phaseolus vulgaris)

A promising strategy for dissolving, mobilizing and enhancing the utilization of the complexed form of phosphorus (P) in soil-plant systems is the use of effective phosphate solubilizing mi-croorganisms. In the present study, six strains of Trichoderma spp. previously obtained from the common bean rhizosphere were investigated for their ability to solubilize tricalcium phosphate (TCP) in NBRIP (National Botanical Research Institute Phosphate) broth medium. All six strains were able to solubilize TCP to various extents, with solubilization ranging from 66.9 mu g/ml to 328.4 mu g/ml. A significant negative linear correlation (r = -0.94; p < 0.01) was found between solubilized P and the pH of the culture medium. The highest solubilization activity (328.4 mu g/ ml), fungal growth (87.21 mg/100 ml) and pH fluctuation (7.0-4.06) were achieved by Tricho-derma gamsii It-62. Under pot conditions, inoculation with Trichoderma gamsii It-62 remarkably improved plant height, shoot and root weight, P uptake, photosynthetic pigments and total pro-tein content compared with untreated common bean seedlings. These increases were significantly higher upon combined inoculation of the bioagent with TCP addition. The obtained results indi-cate that Trichoderma gamsii It-62 might be a promising alternative for the release of fixed forms of phosphates present in the soil, thereby increasing soil fertility.