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Contamination of agricultural land with heavy metal is a serious biological and environmental issue. Such threat can be challenged by exploring the plant symbiotic microbes that can improve plant growth through phyto-hormones secretion and chromate chelation. In the current study, chromate resistant rhizospheric Staphylococcus arlettae strain MT4 was isolated from the rhizosphere of Malvestrum tricuspadatum L. The strain showed potential to secrete phytohormones and plant growth promoting secondary metabolites under induced chromate stress, making it a best suitable candidate in chromate stress alleviation. Moreover, the rhizobacterium MT4 significantly promoted the net assimilation and relative growth rate of sunflower grown in the presence of chromate (100 ppm). Chromate stress alleviation strategy of MT4 strain was three-fold. MT4 alleviated chromate stress and promoted the sunflower growth by suppressing the chromate intake by the host, modulating phytohormones and strengthening of the host's antioxidant system. The improved antioxidant system was confirmed by noticing lower ROS accumulation and improved ROS scavenging, lower peroxidase activity and higher accumulation of phenols and flavonoids. • Staphylococcus arlettae MT4 significantly promotes net assimilation and relative growth rate of Cr stressed sunflower. • MT4 associated seedlings had reduced uptake and higher reduction of Cr. • Strong antioxidant system of MT4 associated seedlings immuned them to grow healthy under Cr stress. [ABSTRACT FROM AUTHOR]

The growth promoting activities of the isolated endophyte Aspergillus terreus from Aloe barbendsis was studied in the salt stressed Pennisetum glaucum (pearl millet). A significant (P = 0.05) increase in the root-shoot lengths, fresh and dry weights and chlorophyll content of pearl millet seedlings was noticed after colonization by A. terreus under normal conditions. At 100 mM NaCl stress and A. terreus inoculation, the growth rate of pearl millet seedlings were significantly (P = 0.05) inhibited. Furthermore, the IAA production, relative water content (RWC), chlorophyll, soluble sugar, phenol and flavonoid contents were significantly decreased, whereas proline content and lipid peroxidation were increased. On the contrary, pearl millet seedlings inoculated with A. terreus retained significantly (P = 0.05) higher amounts of RWC, chlorophyll, soluble sugar, phenol and flavonoid contents under 100 mM salt stress. The higher IAA production in A. terreus associated seedlings rescued the plant growth and development under salt stress. Moreover, the LC MS/MS analysis of A. terreus cultural filtrate revealed the presence of quinic acid, ellagic acid, calycosin, wogonin, feruloylquinic acid, caffeic acid phenylethyl ester, D-glucoside, myricetin, propoxyphene and aminoflunitrazepam. The results of the study conclude that innoculation of A. terreus improves the NaCl tolerance in pearl millet by ameliorating the physicochemical attributes of the host plants. • A potent entophytic fungus isolated from the Aloe barbendsis was tested for plant growth promotion under salinity stress. • The culture filtrate of Aspergillus terreus helped the millet under salinity by influencing the plant endogenous hormones. • Also, A. terreus supported the growth of millet under salinity stress through modulation of secondary metabolites. • The A. terreus acted as a salt stress reliever in millet indicated its potential to be used as bio-fertilizer under stress. [ABSTRACT FROM AUTHOR]