Elevated CO(2) along with inoculation of cyanobacterial biofilm or its partners differentially modulates C–N metabolism and quality of tomato beneficially

Diazotrophic cyanobacteria are known to influence nutrient availability in soil, however, their benefits under elevated CO(2) environment, particularly on fruit quality attributes, is a less investigated aspect. Laboratory developed cyanobacterium-fungal biofilm (An-Tr), composed of Anabaena torulosa (An) as the matrix with the partner as Trichoderma viride (Tr), along with the individual partners were evaluated under ambient (aCO(2)-400 ± 50 ppm) and elevated (eCO(2)-700 ± 50 ppm) conditions, with and without tomato plants. An-Tr inoculation exhibited distinct and significantly higher values for most of the soil microbiological parameters, plant growth attributes and antioxidant/defense enzyme activities measured at 30 and 60 DAI (days after inoculation). Significant enhancement in soil nutrient availability, leaf chlorophyll, with 45–50% increase in the enzyme activities related to carbon and nitrogen assimilation, higher yields and better-quality parameters of tomato, with An-Tr biofilm or An inoculation, were recorded, particularly under eCO(2) conditions. The fruits from An-Tr treatments under eCO(2) exhibited a higher titrable acidity, along with more ascorbic acid, carotenoids and lycopene content, highlighting the superiority of this inoculant. Multivariate analyses revealed significant (p ≤ 0.05) interactions among cultures, DAI, and CO(2) levels, illustrating that cyanobacterial inoculation can be advocated as a strategy to gainfully sequester eCO(2). Significant improvement in yield and fruit quality along with 50% N savings, further attest to the promise of cyanobacterial inoculants for tomato crop in the climate change scenario.