Seedling vaccination by stem injecting a conidial suspension of F2, a non-pathogenic Fusarium oxysporum strain, suppresses Verticillium wilt of eggplant

Several bacterial and fungal strains have been evaluated as biocontrol agents (BCAs) against Verticillium dahliae. In these studies, the BCAs were applied as a root drenching inoculum; however, this application method may have an adverse effect on the native, beneficial for the plants, microbial community. In the present study, it was evaluated whether endophytic application by stem injecting a conidial suspension of the non pathogenic Fusarium oxysporum F2 strain, isolated from a V. dahliae suppressive compost amendment, could reduce significantly Verticillium wilt symptom development in eggplants. It was revealed that stem injection of F2 seven days before transplanting the seedlings to soil infested by V. dahliae microsclerotia resulted in reduced disease severity compared to the control treatment. To visualise F2 ramification into the plant vascular system eggplant stems were injected with an EGFP transformed F2 strain. It was shown that F2 colonises effectively the plant vascular tissues over a long period of time as it was assessed by F2 DNA levels. In parallel, qPCR analysis showed that the application of F2 reduced significantly the amount of V. dahliae DNA in the stem tissues compared to the control treatment.

Graphical abstractStem injection of the non pathogenic Fusarium oxysporum F2 strain resulted to reduced verticillium wilt symptom development in eggplants compared to the control treatment (a). F2 colonised effectively the stem tissues as it was revealed by using a EGFP transformed F2 strain (b).Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Fusarium oxysporum strain F2 has been isolated from a Verticillium dahliae suppressive compost. ► F2 stem injection reduces verticillium wilt in eggplants compared to control. ► F2 endophytic application leads to stem tissue colonisation for a long period of time. ► Real Time PCR showed that F2 inhibited vascular tissue colonization by V. dahliae.