Mitigation of cadmium toxicity induced stress in wheat by acc-deaminase containing pgpr isolated from cadmium polluted wheat rhizosphere

Heavy metals induced stress is a serious threat to crop productivity all over the world. Heavy metals enter the food chain through their uptake by plants and thereby affect human health. Among all the heavy metals, cadmium (Cd) is ubiquitously toxic due to its high water solubility. Cadmium can cause cancer, cardiovascular diseases and neural abnormalities in humans when taken up in the form of food. Keeping in mind the importance of wheat as widely used staple food, a hydroponic glass jar experiment was performed under axenic condition for the screening of most efficient Cd tolerant ACC deaminase containing PGPR from Cd polluted (4.3 mg kg/sup -1/ Cd) wheat rhizosphere. Out of 20 strains, only nine strains were capable of growing at five mg L/sup -1/ Cd level. The most efficient Cd tolerant ACC deaminase containing PGPR that significantly enhanced morphological growth attributes in wheat plants under various levels of Cd (2.5 and 5.0 mg L/sup -1/) were identified as Agrobacterium fabrum (CdtS5) and Stenotrophomonas maltophilia (CdtS7). The photosynthetic pigments were also enhanced significantly in wheat seedlings where Agrobacterium fabrum and Stenotrophomonas maltophilia were applied as an inocula. It is concluded that Agrobacterium fabrum and Stenotrophomonas maltophilia are ACC-deaminase containing PGPR strains which are Cd tolerant, have ability to reduce the Cd uptake by the plant and enhance the wheat growth under Cd toxicity. (author)