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Accueil du site → Doctorat → Espagne → 2017 → Evaluación de enmiendas orgánicas, microorganismos y productos naturales para el control biológico de la Verticilosis en olivo

Universidad de Córdoba (2017)

Evaluación de enmiendas orgánicas, microorganismos y productos naturales para el control biológico de la Verticilosis en olivo

Varo Suárez, Ángela

Titre : Evaluación de enmiendas orgánicas, microorganismos y productos naturales para el control biológico de la Verticilosis en olivo

Evaluation of organic amendments, microorganisms, and natural products for the control of Verticillium wilt in olive

Auteur : Varo Suárez, Ángela

Université de soutenance : Universidad de Córdoba

Grade : Tesis Doctoral 2017

Résumé
One of the most important challenges for the present olive growing is the sustainable control of the Verticillium wilt (VW) disease caused by Verticillium dahliae. Research in several countries of the Mediterranean basin indicates a mean incidence of 1-5% of affected olives, although in some areas of Andalusia region (Southern Spain) disease reaches more than 50%, with a high mortality of trees. The great difficulty of controlling this disease, along with the lack of effective chemicals for the treatment of soil or plant, has motivated the search for alternative methods of control. In this context, biological control appears as an effective and sustainable strategy. In spite of the importance of the disease, there are very scarce and specific research related to biological control of Verticillium wilt in olive. Thus, identifying of potential biological control treatments is currently a major aim for an effective integrated strategy for the control of Verticillium wilt. The first objective of this thesis was to develop a screening method of soil infestation that would reproduce the natural conditions of infection. To overcome the fail in the production of microsclerotia in recalcitrant isolates, a culture medium was optimized for the mass production of microsclerotia and successful soil infestation using previously obtained microsclerotia. However, the most effective inoculation method was soil infestation with the corn meal sand medium (CMS) at 20% w/w. This inoculation method allowed separate treatments for their efficacy, since highly effective treatments (>90% reduction in disease severity) until little or no effective treatments (<10% reduction in disease severity). The selected inoculation method was then used to screen biological treatments for their efficacy against VW in potted olive plants. A second step was conducted to evaluate different microorganisms (fungi, bacteria and their extracts), organic amendments (waste from animals and food industry) and natural substances (essential oils and plant extracts) for the control of V. dahliae. This mass screening of candidates was conducted in four stages : i) in vitro, by the effect on the mycelial growth and spore germination of the pathogen ; ii) in natural infested soil, by the effect on the reduction of microsclerotia of the pathogen ; iii) in plant, by the effect on the infection of olive plants under controlled conditions and iv), in field, by the effect on VW of olive trees grown in highly infested soils. Based on the results of the assessment of 162 treatments under controlled conditions, we have selected 14 biological treatments which have been tested in three field experiments, one of these experiments, FT3, is still ongoing. The nonpathogenic strain of Fusarium oxysporum FO12, and the pomace of grape CGR03 treatments were the most promising candidates, reaching almost the 100% of the inhibition of the disease in controlled conditions and the eradication of the pathogen in naturally infested soil. However, these and other potential treatments must be confirmed in further experiments in field soils with different inoculum densities and soil and climate conditions. The results represent a significant advance in relation to the control of Verticillium wilt in the field, since some of the candidates selected in this work could be available in the near future as effective biological treatments that will help to control this important disease.

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Page publiée le 13 février 2019