Trichoderma harzianum ITEM 3636 colonizes peanut roots as an endophyte and protects the plants against late leaf spot

GIORDANO, DAMIAN FRANCISCO; PASTOR, NICOLÁS ALEJANDRO; ROUWS, LUC FELICIANUS MARIE; DE FREITAS, KARINE MOURA; ERAZO, JESSICA GABRIELA; DEL CANTO, AGOSTINA; DA SILVA COELHO, IRENE; ODDINO, CLAUDIO MARCELO; TORRES, ADRIANA MABEL

SYMBIOSIS

SPRINGER

Lugar: Berlin; Año: 2023

0334-5114

Trichoderma harzianum ITEM 3636 has been tested against diferent soil-borne peanut diseases, applied as a seed treatment. Thestrain protected mature peanut plants suggesting a long lasting protection, and was isolated from plant roots several months after thesowing in feld assays. We hypothesized that T. harzianum ITEM 3636 colonizes peanut roots as an endophyte as was demonstratedwith other few strains, and in this interaction, the fungi reside in plant roots and can protect the plant against a foliar disease. Thespreadability of conidia on the surface of peanut seeds and the mycelial growth inside root tissues were studied through scanningelectron microscopy (SEM) and confocal laser scanning microscopy (CLSM), respectively. Conidia from ITEM 3636 had an appropriate distribution on coated seed surfaces. Furthermore, the fungal mycelium colonized root surfaces forming appressorium-likestructures and swollen cells. The overlay of green and red confocal images clearly showed fungal hyphae grew internally throughepidermal and cortical cells. Once inside the root, T. harzianum ITEM 3636 increased the levels of jasmonic acid in roots but notof salicylic acid. Also, the efect of seed treatment in peanut plant defense against Nothopassalora personata was evaluated undergreenhouse conditions. ITEM 3636 signifcantly decreased the number of afected leafets, late leaf spot (LLS) incidence and severity, and induced higher levels of defense related enzymes in leafets after challenge with the pathogen. No direct activation of JA orSA pathways was observed in the leaves of Trichoderma-induced peanuts plants. T. harzianum decreased the concentration of ABA,which may refect that the strain might improve defense mechanisms of the plant, through ABA content.