Metabolomic profiling unveils differential modulation of tomato fruit quality by microbial interventions

The potential of bio inputs to enhance the organoleptic attributes of tomato, particularly, their nutraceutical benefits and export potential motivated us to develop stimulatory microbial formulations. Towards this endeavour, untargeted metabolic profiling and fruit volatile analysis in 'Pusa Cherry 1' tomatoes were undertaken, to analyse the differential elicitation of metabolites by microbial interventions. Treatment with cyanobacterium Anabaena laxa enhanced the fruit lycopene content by 1.13-fold while, a mesocarpic bacterium- Enterobacter cloacae enhanced the fruit lycopene, phenolics and flavonoids by 1.07, 1.5 and 2.54-fold respectively; combined inoculation led to 1.25 and 1.68-fold increase in phenolics and flavonoids, compared to control fruits. Untargeted metabolome analyses of fruits revealed A. laxa mediated enrichment of spermidine and benzoquinone and likely, induction of plant's antioxidant defense system and hormonal modulation, towards enhanced lycopene content and accumulation of benzenoid derived floral volatiles. High lycopene, flavonoid and ascorbic acid content along with carotenoid and lipoxygenase derived fruity volatiles in the fruits of E. cloacae treatment can possibly be associated with the stimulation of sphingolipid metabolism, lipoxygenase mediated oxylipin synthesis and the accumulation of S-adenosyl methionine, both suggesting jasmonate/ethylene mediated induced systemic resistance. Enrichment of α-ketoglutarate, amines, purines and pyrimidines besides S-adenosyl methionine, sphingolipid and rutin accumulation in the fruits due to co-inoculation of A. laxa and E. cloacae was also supported by 20.4% increase in fruit yield. It is noteworthy that both the microbes elicited distinct modes of defense system activation and co-ordinated hormonal responses which influenced fruit overall ripeness, nutritional and sensory quality, along with increased fruit yield.