Suppression of strawberry anthracnose by Paenibacillus polymyxa TP3 in situ and from a distance

Abstract

Strawberry is a popular fruit with valuable nutrition and an attractive fragrance, but its production and propagation are limited by various diseases, such as anthracnose and gray mold. For disease management, biological control measures are environmentally friendly and good alternatives to fungicides to avoid crop losses, reduce carbon emissions, and improve food safety. In this study, Paenibacillus polymyxa TP3, which originated from the strawberry phyllosphere, was shown to antagonize the anthracnose fungal pathogen Colletotrichum siamense and reduce leaf symptoms on strawberry plants. Several fusaricidin-corresponding mass spectra were detected in the confrontation assay of P. polymyxa TP3 and C. siamense by image mass spectrometry. The transcription of fusA and fusG in the fusaricidin biosynthesis gene cluster increased while P. polymyxa TP3 was cultured in the medium containing the culture filtrate of C. siamense, as detected by reverse transcriptase-polymerase chain reaction, indicating the involvement of fusaricidins in P. polymyxa TP3 antagonism of the anthracnose pathogen. Further disease control assays demonstrated the time frame and spatial mode of P. polymyxa TP3-induced systemic resistance of strawberry against C. siamense. The transcript level of the marker gene FaPDF1.2 of the jasmonic acid pathway was increased in strawberry leaves after drenching treatment with P. polymyxa TP3, and the callose deposition was enhanced by further flg22 treatment. In addition, P. polymyxa TP3 treatments of the mother strawberry plants reduced C. siamense infection in the daughter plants, which would be a potent feature for the application of P. polymyxa TP3 in the strawberry nursery and the field to reduce the disease impact, especially of anthracnose.