S.V. Humbarwadi1 and R.P. Patil
Abstract
Heavy metal poisoning is mostly caused by the emission of hazardous pollutants through various natural and anthropogenic activities. Copper (Cu) is an essential micronutrient for plants; it is required in relatively small amounts for proper growth and development. However, like many elements, copper also has negative effects on plants at its high concentration. Soil testing and proper agricultural practices can help prevent copper toxicity issues. In the present research, a PPL bioinoculant was prepared from three previously isolated and identified Cu-tolerant Providentia, Paenibacillus, and Lysinibacillus PGPR (plant growth promoting rhizobacteria) strains. In vitro testing of prepared PPL bioinoculant was done for its plant promotion activity and its effect on Cu accumulation by marigold (Tagetus erecta) plant using pot assay. Activities promoting plant growth, such as production of siderophores, indole acetic acid, hydrogen cyanide (HCN), and phosphate solubilization were measured in vitro. PPL bioinoculant influenced the growth of marigold plant both directly and indirectly. The introduction of a PPL bioinoculant under Cu stress led to a decrease in Cu phytotoxicity, while the root length, shoot length, fresh weight and dry weight of the marigold plant increased in comparison to the uninoculated control. In addition, compared to uninoculated control plants, the total Cu accumulation was also increased in marigold plant inoculated with PPL bioinoculant. According to our findings, metal tolerant PGPR are a very promising resource that could provide great bio-inoculants to increase the effectiveness of phytoremediation.