Agroecological functions of Trichoderma harzianum , an endophytic fungus of the avocado root: its role in plant growth, defense and multitrophic interactions

BACKGROUND: Trichoderma is a key rhizosphere fungus, yet its ecological role in avocado (Persea americana) physiology and multitrophic interactions remains largely unexplored. This study evaluates the impact of Trichoderma harzianum TH1 on plant growth, defense mechanisms and natural enemy recruitment. RESULTS: CFU/g. Inoculation significantly promoted growth, increasing leaf formation by 23% and showing a 2-fold increase in leaf bud production. Furthermore, TH1 conferred resistance against the avocado mite Oligonychus perseae and the whitefly Tetraleurodes perseae, reducing whitefly populations >85%. This resistance was linked to a 27% increase in chlorophyll production and a 4-fold rise in salicylic acid (SA) levels, a key metabolite for systemic defense against sap-sucking herbivorous insects. Chemical analyses of volatile organic compounds (VOCs) revealed the emission of (Z)-3-hexen-1-ol, 1-octen-3-ol, β-ocimene, and β-copaene. These semiochemicals likely mediated the 2-fold increase in predatory mites (Euseius hibisci) observed in TH1-treated plants. Additionally, the presence of parasitoid wasps (Encarsia sp.) was recorded within the recruited natural enemy complex on avocado leaves. CONCLUSION: This study elucidates the biochemical and biotic factors involved in the avocado-TH1-arthropod interaction. Our results support the use of T. harzianum as an effective bioinoculant to enhance plant growth and suppress pests, offering a sustainable alternative to synthetic agrochemicals.