Effect of Elevated Tropospheric Ozone on Vigna Mungo L. Varieties

ABSTRACT Tropospheric ozone (O3) is widely recognized as the most critical, regional atmospheric pollutant causing significant losses to agricultural productivity due to its phytotoxicity over agricultural areas and is expected to increase in future. In view of rising tropospheric ozone concentration over Indian regions, the present study aimed to evaluate the effect of elevated ozone stress on pulse crop blackgram (Vigna mungo L.), which contributes the major share of protein. The blackgram varieties namely CO 6, VBN 1, VBN 2, VBN 3, VBN 5, VBN 6, VBN 7, and VBN 8 were grown in open top chambers and factorial completely randomized block design was followed. The plants were exposed to elevated ozone concentration (50 and 100 ppb) from 10.00 h to 17.00 h over 10 days at flowering stage, with a weighted average ozone concentration of 50.1 and 101.2 ppb. Both the elevated ozone treatments significantly affected the plant physiological, biochemical, growth, and yield traits of all test varieties. On an average across eight blackgram varieties, decrease in chlorophyll content by 33.83 and 42.41%, stomatal conductance by 28.25 and 40.51% and photosynthetic rate by 29.43 and 42.30% exposed to 50 and 100 ppb ozone were observed, respectively. Correspondingly, the number of pods per plant decreased by 30.82 and 32.65%, 100 grain weight by 7.75 and 21.23% and plant weight by 16.03 and 21.23%, respectively, which were significant at 5% level. Furthermore in the observed traits, significantly higher reduction was observed in VBN3, while the least reduction was observed in VBN8. The path analysis displayed that all the observed physiological, biochemical, growth, and yield traits positively regulated the yield except leaf injury percentage, malondialdehyde, and proline content. The principal component analysis of two elevated ozone treatments confirmed VBN8 as ozone tolerant and VBN3 as ozone sensitive variety. Hence, cultivation of VBN8 variety at ozone hotspot regions would be the best option to overcome ozone induced yield loss.