Abstract
Bioavailability of cadmium (Cd) metal in the soils due to the scarcity of good quality water and industrial waste could be the major limiting factor for the growth and yield of crops. Therefore, there is a need for a prompt solution to the Cd toxicity, to fulfill increasing food demand resulting from growing world population. Today, a variable range of plant growth promoting rhizobacteria (PGPR) is being used at a large scale in agriculture, to reduce the risk of abiotic stresses on plants and increase crop productivity. The objective of this study was to evaluate the efficacy of Bacillus siamensis in relieving the Cd induced damage in two wheat varieties (i.e., NARC-2009 and NARC-2011) grown in Cd spiked soil at different concentrations (0, 20, 30, 50 mg/kg). The plants under Cd stress accumulated more Cd in the roots and shoots, resulting in severe oxidative stress, evident by an increase in malondialdehyde (MDA) content. Moreover, a decrease in cell osmotic status, and alteration in antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) were also observed in wheat plants under Cd stress. As a result, the Cd exposed plants showed a reduction in growth, tissue biomass, photosynthetic pigments, membrane stability, total soluble sugars, and amino acids, in comparison to control plants. The extent of damage was observed to be higher with an increase in Cd concentration. However, the inoculation of wheat with B. siamensis improved plant growth, reduced oxidative stress, and enhanced the activities of antioxidant enzymes in both wheat varieties. B. siamensis amendment brought a considerable improvement in every parameter determined with respect to Cd stress. The response of both wheat varieties on exposure to B. siamensis was positively enhanced, whereas NARC-2009 accumulated less Cd compared to NARC-2011, which indicated a higher tolerance to Cd stress mediated by B. siamensis inoculation. Overall, the B. siamensis reduced the Cd toxicity in wheat plants through the augmentation of the antioxidant defense system and sugars production.
Highlights
Agriculture is considered the big source of economy and the basic livelihoods of people in several countries of the world [1]
The results of the present study depicted that inoculation of B. siamensis positively enhanced the growth and biomass of both wheat varieties grown in Cd-contaminated soil (Figure 1)
The Cd-stress at all tested concentrations (20, 30, and 50 mg/kg) decreased the growth and biomass of wheat whereas, maximum reduction was observed with Cd-50 mg/kg
Summary
Agriculture is considered the big source of economy and the basic livelihoods of people in several countries of the world [1]. Agriculture as a pillar in the food industry is expected to provide food for the world’s increasing population [2]. The global agricultural regions, including cereals and especially wheat, are facing a wide spectrum of challenges, such as biotic and abiotic stresses under normal conditions [3]. The cadmium (Cd) is thought to be a very toxic entity, non-biodegradable, bio-accumulative, and a major wheat yield-limiting factor [5]. Cd enters the environment via geogenic and anthropogenic sources, such as fertilizer, sewage slough dispersal, industrial waste, electroplating, and atmospheric deposition [6]
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