Efficiency of protectants in alleviating ozone stress on rice cultivars (Oryza sativa L.)

Tropical countries like India, as a result of increased greenhouse gases like tropospheric ozone (O3), are concerned about a loss of agricultural output and food security. As a result, adopting a new method to protect crops against ozone is a must. The most efficient protectant is ethylene diurea (EDU), which is often used by researchers, however, the effectiveness of other protectants remains still unexplored. Hence, this study aims in screening the potential protectants in alleviating the ozone stress (100 ppb) in O3 sensitive rice cultivar in open top chambers. The protectants used includes neem coated urea (NCU), ascorbic acid (AsA), calcium acetate (CaAc), panchagavya, neem oil, pink pigmented facultative methylotrophs (PPFM) and ethylene diurea (EDU). Results indicate that besides EDU, NCU and AsA were highly effective in mitigating O3 stress and were on par with each other. The application of protectants significantly improved the physiological, growth, and yield attributes; while, the malondialdehyde and proline content declined. The effect of protectants was relatively higher in O3 – sensitive cultivar. . The growth and yield traits were observed to be higher in EDU > NCU, AsA > CaAc > Panchagavya > Neem oil > PPFM. In O3 – sensitive cultivar, application of 300 ppm EDU, 1% NCU, and 1% AsA decreased the malondialdehyde content by 26.82, 26.92 and 27.47%, and proline by 18.64, 17.88 and 14.33%, respectively. Similarly, the application of 300 ppm EDU, 1% NCU and 1% AsA improved the number of spikelets per panicle by 69.09, 63.64 and 58.15% and the number of filled spikelets per panicle by 95.97, 95.35 and 93.02%, respectively. The present study concludes that NCU and AsA are the best alternatives to EDU for protecting plants against ozone stress.