The nonpathogenic strain of Fusarium oxysporum FO12 induces Fe deficiency responses in cucumber (Cucumis sativus L.) plants

Abstract

Rhizosphere microorganisms can elicit induced systemic resistance (ISR) in plants. This type of resistance involves complex mechanisms that confer protection to the plant against pathogen attack. Additionally, it has been reported by several studies that ISR and Fe defciency responses are modulated by common pathways, involving some phytohormones and signaling molecules, like ethylene and nitric oxide (NO). The aim of this study was to determine whether the nonpathogenic strain of Fusarium oxysporum FO12 can induce Fe defciency responses in cucumber (Cucumis sativus L.) plants. Our results demonstrate that the root inoculation of cucumber plants with the FO12 strain promotes plant growth after several days of cultivation, as well as rhizosphere acidifcation and enhancement of ferric reductase activity. Moreover, Fe-related genes, such as FRO1, IRT1 and HA1, are upregulated at certain times after FO12 inoculation either upon Fe-defciency or Fe-sufcient conditions. Furthermore, it has been found that this fungus colonizes root cortical tissues, promoting the upregulation of ethylene synthesis genes and NO production in the root subapical regions. To better understand the efects of the FO12 strain on feld conditions, cucumber plants were inoculated and cultivated in a calcareous soil under greenhouse conditions. The results obtained show a modifcation of some physiological parameters in the inoculated plants, such as fowering and reduction of tissue necrosis. Overall, the results suggest that the FO12 strain could have a great potential as a Fe biofertilizer and biostimulant.