Exogenous AMF with Glycine Betaine Reduces Cr (VI) Uptake and Alleviates Chromium Toxicity by Supressing the Oxidative Stress in Three Genetically Different Sorghum (Sorghum bicolor L.) Cultivars

Abstract

Background: Chromium is most toxic pollutant that negatively affects plant’s metabolic activities and yield. It reduces plant growth by influencing the antioxidant defense system’s activities. The aim of the present research was to examine the ameliorative capability of exogenous GB and AMF spiked in soil, either individually or in combination against Cr toxicity. The ameliorative effects were studied in terms of Cr uptake, grain yield, antioxidative defense system parameters (viz. enzymes – SOD, APX, CAT, GR, POX and metabolites – proline, glutathione, ascorbate, β-carotene) and indices of oxidative stress parameters (viz. PPO, H2O2, and MDA). Results:The results delineated that Cr uptake and indices of oxidative stress were increased with increasing concentration of Cr stress in all the varieties (HJ 541, HJ513 & SSG 59-3) at both the growth stages (35 & 95 DAS). At higher concentration (4 ppm), Cr stress decreased the grain yield (45-50%) as compared with controls. PPO activity, MDA and H2O2 content increased at both growth stages in all the varieties. However, antioxidative enzymes and metabolite activities increased due to Cr stress but this increase was not sufficient to counteract with ROS generated under Cr stress which was enhanced on the application of AMF and GB either individually or in combination (spiked in soil). It decreased the indices of oxidative stress and ameliorated the Cr toxicity and increased grain yield (65-70%) in all the varieties. Conclusions:Both GB and AMF, improved the plant growth and stress tolerance capacity of the plant. GB at both 50 and 100 mM level, significantly ameliorated Cr (VI) toxicity. However, AMF concomitantly with GB further boost up the amelioration behavior of the plant against Cr toxicity, at both growth stages in all the varieties. The combination of 100 mM GB with 10 g AMF was observed most effective among all the treatments. Among the varieties SSG 59-3 had the lowest chromium uptake, indices of oxidative stress, and highest antioxidative system’s activity as compared to HJ 513 followed by HJ 541 variety. Thus AMF and GB either individually or in combination may be used to maintain plant yield attributes under Cr toxicity.