Biological control of Verticillium wilt of olive by Trichoderma harzianum

Trabajo presentado en la XIII Meeting of the IOBC Working Group "Biological Control of Fungal and Bacterial Plant Pathogens", celebrada en Uppsala del 15 al 18 de junio de 2014.Verticillium wilt of olive tree (Olea europaea L.) (VWO), ca u sed by the soil-borne fungus Verticillium dahliae Kleb., is considered one ofthe most devastatíng diseases affecting this crop in many areas. Preventive measures su eh as the treatment of the root systems at the nursery stage with microbial antagonists emerges as a promising altemative. Species ofthe soil-borne fungus Trichoderma ha ve been widely described as biocontrol agents (BCAs) of severa[ phytopathogenic fungi by means of different mechanisms. In this study we aimed to evaluate the potential of T harzianum CECT 2413 as effective BCA of VWO. Strain CECT 2413 was shown to in vitro overgrow both the bighly-virulent, defoliating (D) and the midly-virulent, non-defoliating (ND) V. dah!iae pathotypes infecting olive. Inhibition of V dahliae growth in cHituring media where strain CECT 2413 had previously grown showed that this ability might be dueto excretion of secondary metabolites or cell wall degrading enzymes. Wben a suspension of conidia of T harzianum CECT 2413 were applied by irrigation to roots of nursery-propagated, three-month-old olives (cv. Picual) prior to the treatment with a D isolate ofthe pathogen, disease symptoms were significantly reduced compared to that observcd in control plants. M oreo ver, increase in the number and size of lea ves in plants treated \vith Trichoderrna was also reported. Biofonnulations ofthis BCA, alone or in combination with other Trichoderma spp. strains, have been recently patented and licensed.Supported by ERDF-­cofinanced grants (AGR-­‐6038, AGR-­‐5948, Consejería de Economía, Innovación y Ciencia, Junta de Andalucía, Spain, and NUTESCA S.L. (Jaén, Spain).N