Role of Trichoderma and Sinorhizobium Strains for Improving Growth and Nutritional Status of Alfalfa under Cd Stress

The plant rhizosphere is a major soil ecological environment for plant- microbe interactions involving colonization of different microorganisms in and around the roots of the growing plant. Plants can be used in the remediation of soils contaminated with heavy metals. The objective of this study was determine the relationship between the effect of Cd on the symbiotic model of Sinorhizobium meliloti – Medicago sativa and the application of Trichoderma sp. on the nutritional status as well as biochemical characterization of the sandy brown forest soil. The effects of biofertilizer Sinorhizobium and coinoculants Trichoderma strains on growth, chlorophyll and N, P and K content of alfalfa growing in soil polluted by cadmium were investigated. The results indicate that the presence of the saprobe fungi Trichoderma harzianum further enhanced shoot dry weight, N, P and K content of Sinorhizobium meliloti-alfalfa symbiotic model. The co-inoculation of alfalfa with T. harzianum was more effective for Cd uptake. The effects of the bio-multiple inoculants on the growth of alfalfa were stimulated the colonization of Sinorhizobium strains in the rhizosphere, promoted the nodulation potential and increased the dry organic matter. Sinorhizobium meliloti interacts with alfalfa as a model for rhizobioremediation and Trichoderma strains interact with this model as nodule promotors as well as a partner in the process of cleaning the plant rhizosphere from cadmium metal.