Seed treatment with Mortierella alpina M01 promotes tomato growth and mitigates verticillium wilt and bacterial speck disease infections by potentiating plant antioxidant responses

Abstract

Almost 85% of tomato plants in the world are grown in controlled greenhouse. This confined microclimate forms a favorable environment for the fast development of pathogens. This study evaluates the use of Mortierella alpina M01 strain as a plant growth-promoting fungus and biocontrol agent for tomato plants in greenhouses. Its bio-eliciting effect on growth, photosynthetic traits, and fruit yield, together with its protective ability against verticillium wilt and bacterial speck diseases was assessed. The treatment of tomato seeds with M. alpina M01 spore suspension significantly enhanced tomato growth variables such as stem length, leaf and leaflets numbers, and root and fruit biomass. It improved photosynthesis efficiency, stomatal conductance, and transpiration rate. Concerning plant immunity, M. alpina M01 lowered leaf alteration index by 31% and browning index by 86%, mitigating the damage inflicted by Verticillium dahliae in tomato. Likewise, M. alpina M01 was effective in reducing disease score and average of number of lesions caused by Pseudomonas syringae pv. tomato by 48 and 76%, respectively. M. alpina M01 modulated lipid peroxidation triggered by V. dahliae or Ps. pv. tomato infestations, by potentiating H₂O₂ accumulation and the activity of the antioxidant enzymes GPOD or PPO. Finally, phenolic and flavonoid contents increased after inoculation with the bacterial pathogen in M. alpina M01-pre-treated plants, implying primed defenses. These results highlight the potential of M. alpina M01 as a PGPF to improve tomato growth, and as a biocontrol agent against V. dahliae and Ps. pv. tomato in controlled confined environments such as greenhouses.