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Heavy metal (HM) contamination in the soil and accumulation in plants poses a serious threat to crops and human health. HMs such as cadmium, mercury, lead and arsenic are widely acknowledged for their adverse effects on plants such as chlorosis, necrosis, low food quality and crop yields. Endophytic fungi secrete secondary metabolites and enhance the plant's ability to tolerate stressful conditions. However, the role of most fungal endophytes in their host plant growth or production of metabolites under HM stress conditions needs further understanding. In the present study, we studied the HM stress alleviation capability of the endophytic fungus, Paecilomyces lilacinus (MRF), isolated from the roots of Justicia adathoda. We studied two heavy metals, namely lead and cobalt. The culture filtrate (CF) of P. lilacinus revealed IAA (68.17 µg/mL), phenols (43.31 µg/mL), flavonoids (40.59 µg/mL), sugar content (97.83 µg/mL) and proline (17 µg/mL). Additionally, DPPH-free radical scavenging activity and the antibacterial potential against Salmonella typhi and Shigella sonnei of the CF demonstrated positive results. The gas chromatography mass spectrometry analysis of the CF manifested different constituents, including (1) Trichloromethane, (2) 3,7,11,15-Tetramethyl-2-hexadecen-1-ol, (3) phytol, (4) 1,2-Benzenedicarboxylic acid, (5) bis(2-ethylhexyl) ester, (6) squalene and (7) Cyclotrisiloxane Hexamethyl. Moreover, the plant growth-promoting activity of the P. lilacinus (MRF) strain revealed a robust increase in root and shoot growth, and the fresh and dry weight of S. lycoprsicum. Further, the IAA, phenols, flavonoids, sugar, proline, relative water content and protein contents also increased in the S. lycoprsicum inoculated with P. lilacinus as compared to the control plants. The present study revealed that the inoculation of P. lilacinus alleviates the damages of HM stress and improves the physicochemical characteristics of S. lycoprsicum. [ABSTRACT FROM AUTHOR]

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]