Reduction of verticillium wilt in tomato by an arbuscular mycorrhizal fungus - Rhizophagus intraradices and an endophytic fungus - Penicillium pinophilum is cultivar dependent

Abstract

Verticillium wilt is a major concern in vegetable production due to its broad host range, world-wide distribution, vascular colonization, and resilient microsclerotia. This study was conducted to evaluate the growth and tolerance to Verticillium dahliae in two tomato cultivars inoculated with arbuscular mycorrhizal fungi (AMF)- Rhizophagus intraradices 15S-1 and an endophytic fungus- Penicillium pinophilum EU0013. In a randomized factorial layout, seedlings of tomato cultivars (Momotaro, Rodeo) were inoculated with beneficial microbes and V. dahliae pathogen and raised until maturity under greenhouse condition. In vitro dual culture indicated the growth inhibition of V. dahliae by P. pinophilum after one month on PDA media. Root colonization by R. intraradices and P. pinophilum were modulated in response to V. dahliae in a cultivar-dependent manner. While Momotaro showed greater foliar and internal disease symptoms than Rodeo, P. pinophilum and R. intraradices significantly reduced disease incidence, compared to control. Verticillium-induced reductions in root and fruit dry weights in Rodeo and Momotaro were reduced by P. pinophilum, while AMF generally boosted fruit weights. Co-inoculation of R. intraradices and P. pinophilum did not consistently improve host growth indices compared to single inoculation, and modulations in mineral element nutrition by both beneficial microbes in response to V. dahliae was cultivar dependent. In Momotaro, R. intraradices and P. pinophilum increased SlSOD2, SlSOD5 and SlSOD9 gene expression, but this was not generally the case in Rodeo, where lower expression levels were observed. Cultivar-dependent modulation of root colonization, element nutrition, and SlSODs gene expression, by R. intraradices and P. pinophilum underpin their promotion of host growth and tolerance to verticillium wilt.