Interaction of chromium (Cr) resistant plant growth promoting rhizobacteria with compost to phytostabilize Cr in spinach rhizosphere
Muhammad Junaid Sarwar, Muhammad Shabaan, Hafiz Naeem Asghar, Muhaimen Ayyub, Qasim Ali, Usman Zulfiqar, Muhammad Nazim, Khaloud Mohammed Alarjani, Mohamed S. Elshikh
Abstract
Chromium (Cr) is classified as an ecological toxin, and irrigation of soil with raw industrial effluents causes its concentration in soil and plants to reach fatal levels. Due to reduced metal mobility caused by organic amendment and availability of food for microbial activity, use of Cr-tolerant rhizobacteria in conjunction with compost has proven to be useful in supporting development and survival of plants. We checked the simultaneous effects of rhizobacteria and compost on spinach (Spinacia oleracea) growth, physiology, biochemistry and uptake of Cr. Plants were treated with compost (1% w/w) and subsequently inoculated with two different PGPR strains under Cr contamination. Among inoculated strains, 'JS2′ strain along with compost significantly ameliorated the adverse effects of Cr on spinach, and improved root and shoot lengths (84, 197%), as well as dry (104 and 89%) and fresh (89 and 167%) weights of roots and shoots, along with chlorophyll content (84%) compared to the relative control. In addition, combined application led to a significant increase in antioxidant activities, such as SOD (128%), CAT (40%), POD (73%), and APX (57%) concomitant with decreased MDA contents (68%). Data regarding Cr movement from soil to roots and aboveground plant parts, as well as the results of translocation and bioconcentration factors, revealed that combined application of PGPR and compost reduced Cr entry to aboveground plant parts and led to its phytostabilization. Hence, compost and Cr-tolerant PGPR can efficiently immobilize Cr in soil and reduce its harmful effects on spinach growth, physiology and other attributes.