Endophytic Aspergillus niger reprograms the physicochemical traits of tomato under cadmium and chromium stress

This study aimed to evaluate the effect of endophytic fungi isolated from Cucurbita roots on growth, physiological, biochemical and molecular attributes of Solanum lycopersicum L. under Cd and Cr stress. The initial screening experiments on Oryza sativa L. seedlings revealed a plant growth promoting endophyte (Cu-17) out of the 17 isolated strains. The strain was identified as Aspergillus niger by amplifying ITS region of 18 S rDNA. A pot experiment was set to evaluate the effect of A. niger on S. lycopersicum exposed to two different concentrations (100 ?g/g and 500 ?g/g) of Cd and Cr. A. niger alleviated Cd and Cr stress in S. lycopersicum by reducing its translocation to the aerial parts of the host plant. A. niger also enabled the S. lycopersicum to produce significant amounts of IAA, proline, flavonoids, phenols, catalase (CAT) and ascorbic acid oxidase (AAO), in addition to sugar and proteins. Moreover, A. niger facilitated the S. lycopersicum to induce stress responsive genes (SlGSH1 and SlPCS1) in order to develop tolerance against the Cd and Cr stress. Both SlGSH1 and SlPCS1 genes helped the S. lycopersicum to chelate Cd and Cr and thus mitigate their toxicity. The results, therefore, conclude that A. niger might be used as biofertilizer for healthy and safe crop production in Cd and Cr contaminated soils.