Bacillus siamensis Reduces Cadmium Accumulation and Improves Growth and Antioxidant Defense System in Two Wheat (Triticum aestivum L.) Varieties

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.

Mitigation of Copper Stress in Maize by Inoculation with Paenibacillus polymyxa and Bacillus circulans

“…The two strains accelerated the absorption and transport of minerals via carriers under Cu stress, which in turn could maintain the synthesis of pigments [66,80,81] even under Cu stress. These results are in harmony with the results of Kamran et al [82] and Awan et al [36].…”

“…In the present work, elevated content of osmolytes under Cu doses under PGPR inoculation could have preserved sustained redox homeostasis which resulted in optimal plant metabolism. A similar increase in osmolytes content under metal stress by PGPR inoculation was reported in maize [36,85], sunflower [26], rape seedlings [86], potato [24], tomato [87], curtis [88] and lentil [89] plants. Interestingly, the inoculation with Pp and Bc diminished the accumulation of proline content in the Cu stressed seedlings (Figure 1A,B), which is linked with enhanced growth of maize plants under Cu stress (Table 1).…”

“…In earlier reports, it has been concluded that maize seedlings inoculated with PGPR have shown tolerance to salt [30,31], Al and salt [32], Cd [33], drought [34] and chilling [35] stresses. Application of Bacillus siamensis to wheat plants showed improved tolerance to Cd stress by restricting the accumulation of Cd and boosting the antioxidant defense system [36]. However, research regarding underlying mechanisms of inoculation of maize plants with phosphate-and potassium-solubilizing bacterial strains P. polymyxa and B. circulans under Cu toxicity receive little attention.…”

ADAPTATION AND TOLERANCE OF WHEAT PLANTS TO DROUGHT MEDIATED BY NATURAL GROWTH REGULATORS Bacillus spp.: MECHANISMS AND PRACTICAL IMPORTANCE (review)

“…PGPB Bacillus spp. -большая и разнообразная группа полезных непатогенных микроорганизмов, свободно живущих в почве либо населяющих поверхность (ризосферу и филосферу) или внутреннюю часть тканей (эндофиты) растений-хозяев, cпособных индуцировать рост и устойчивость растений к биотическим стрессорам -фитопатогенам (19)(20)(21)(22), насекомым-вредителям (20), нематодам (19), вирусам (20) и абиотическим стрессам -засухе (17,24), засолению (11), перепадам температур (12), токсичным соединениям (14), УФ-излучению (12,13). Это продемонстрировано на примере многих видов растений (17,(25)(26)(27)(28), включая пшеницу (13,(29)(30)(31).…”

Praseodymium enhanced the tolerance of maize seedlings subjected to cadmium stress by up-regulating the enzymes in the regeneration and biosynthetic pathways of ascorbate and glutathione

“…It has been reported that biotic and abiotic factors could improve the Cd tolerance of plants. Awan et al (2020) reported that Bacillus siamensis enhanced the Cd tolerance of wheat plants. Khanna et al (2019) found that plant growth-promoting rhizobacteria alleviated Cd toxicity in Solanum lycopersicum L. seedlings.…”