Requirement for nickel as an essential nutrient for growth of plants, is very low and increasing its level caused to environmental pollution and toxic effects on plants. Piriformospora indica is a root fungus, which denotes several profits to plants including increase growth and their performance under both non-stress and stress circumstances. It has been observed that P. indica increases tolerance / resistance of plants to various stresses caused by biotic/abiotic factors like diseases and heavy metals. We analyzed the useful impacts of P. indica on tomato plants during nickel stress conditions (300, 600 and 900 mg L-1) in three lab, greenhouse and aeroponic experiments. The growth traits of tomato such as root length and root dry weight were found to be positively enhanced in P. indica treated tomato plants as compared with non-treated plants. Treating of P. indica thwarted the harmful effects of nickel in anthocyanin, proline, catalase and glutathione peroxidase while it could decrease the adverse effects of nickel at different levels on hydrogen peroxide and it decreased significantly. However, nickel-stressed plants indicated much better in the presence of the fungus compared with non-treated plants in most of the measured traits. The photosynthetic pigments (chlorophyll a and b, and carotenoids) were significantly higher in P. indica treated tomato plants under high nickel stress circumstances as compared with non-treated P. indica plants under non-nickel stress, in which these pigments were found to be decreased. Proline production was seen during P. indica inoculation, which may aid the treated plants to become nickel stress tolerant. Finally, the present investigation completed our knowledge in using P. indica symbiosis in inducing the heavy meat tolerance like nickel in tomato for achieving to sustainable agriculture targets.
