Lettuce tolerance to verticillium wilt after inoculation with Penicillium pinophilum and Rhizophagus intraradices

The ability to mitigate verticillium wilt is an important attribute of a biocontrol agent in terms of its global market potential. This study evaluated the protective effect of an arbuscular mycorrhizal (AM) fungus and an endophytic fungus (Penicillium pinophilum) inoculation against verticillium wilt in lettuce host. The seedlings in four treatment groups (control, AM, Penicillium, AM + Penicillium) were raised for six weeks in the presence or absence of the pathogen (Verticillium dahliae) in a growth chamber. The foliar disease incidence was evaluated and recorded as 37 %, 35 %, 3 %, and 14 % for Control, AM, Penicillium, and dual inoculated treatments, respectively. V. dahliae decreased the plant growth indices, carbon, and nitrogen contents in all groups, except in Penicillium treatment. Trace elements concentrations were reduced due to disease across board, but manganese (Mn) was modulated by the endophyte. R. intraradices and its co-inoculation with P. pinophilum did not confer protection to lettuce, despite having lower quantity of pathogen DNA in their stems than Control and Penicillium inoculated plants. In mitigating the negative effect of V. dahliae, aside in vivo pathogen antibiosis, the endophyte modulated reactive oxygen species, nitrogen, manganese, and improved host growth indices, thereby, gave the most effective bio-protection. However, its co-inoculation with the R. intraradices reduced its efficacy.