(1177-B) Nanopollution- Inhibitory effect of CuO NPs in tolerant and susceptible variety of rice (Oryza sativa L.) with conflicting levels of stress tolerance.

Abstract: The widespread application of metal oxide-based nanoparticles has skyrocketed due to their unique features in various industrial realms. However, the reckless use and hysterical discharge of NPs pose a major threat to the growth and yield patterns of the rice plant. The study highlighted the impact of CuO NPs in susceptible (PB 1) and tolerant rice (PB 1637) variety at two growth stages (after 21 and 120 DAT- days after transplanting) for conducting comparative physicochemical-soil properties, growth, oxidative stress indices, gene expression, and yield parameters. Both varieties of rice were cultivated for grain production in soil amended with dissimilar CuO NPs concentrations. Based on the growth conditions after 21 DAT and the growth-yield results after 120 DAT, the threshold level was found between 100–200 mg/kg CuO NPs which eventually results in detrimental consequences in the growth-yield pattern of rice plants. The results demonstrated that after 21 DAT at higher doses of CuO NPs, the tolerant variety (PB 1637) has a lower toxic effect on growth attributes (shoot, root length, fresh wt. of shoot and root) with respect to susceptible variety. Furthermore, the results highlight that, after 120 DAT, CuO NPs declined the plant yield growth, number of tillers, PAL, SN, TPW and TGW respectively more in susceptible than tolerant variety. Alongside, based on the above results, the selected inhibitory concentration of CuO NPs also augment the oxidative stress markers i.e., (SOR, H2O2 and MDA) levels within plant leaves which mediate oxidative stress higher in susceptible variety than tolerant ones. Whereas, the results pertaining to antioxidant enzyme activities and gene expression patterns showed a differential pattern at both growth stages. Subsequently, after 21 DAT at selected conc. of CuO NPs, production of SOD was significantly higher in the sensitive variety while CAT and GST were enhanced in the tolerant variety.
In contrast, after 120 DAT, a boost in the efficiency of SOD and CAT in the tolerant (P>0.05) than sensitive variety was observed, whereas the activity of GST was declined significantly in both varieties under CuO NPs supplementation. Further, entire data was validated by gene expression pattern by qRT-PCR. Rsults showed differential expression patterns of antioxidant genes of the Ascorbate Glutathione pathway (APX, DHAR, MDHAR and GR) and copper transporter (COPT 7) at both growth stages. Subsequently, the present findings provide new avenues towards these issues and provide novel insights to understand the unknown toxic behavior of NPs in soil that may help to understand the inbuilt detoxification mechanisms to confer stress tolerance capacity in rice crop through OMICS approach.
Keywords- Rice, tolerant, susceptible, variety, yield, growth, oxidative stress, antioxidant, gene