Grape phylloxera Daktulosphaira vitifoliae destroyed 30% of the European vineyard by the end of the 19th century, attacking the woody roots of the grapevine Vitis vinifera (L.). To date, grafting grapevine on American resistant rootstocks is the leading solution to control the pest. However, grape phylloxera is present in most wine-growing soils and remains a threat in regions planted with non-grafted vines. Thus, alternative control solutions are investigated. The entomopathogenic fungus Metarhizium robertsii is known for its capacity to parasitize insects. Besides, the fungus can colonize plant rhizosphere and establish as an endophyte (i.e., within plant tissues) in many plant species. The thesis aimed to investigate if M. robertsii could persistently associate with the rhizosphere and as an endophyte in non-grafted grapevine V. vinifera without harming its growth while preventing the development of the grape phylloxera radicicole forms.Four M. robertsii strains native to four different vineyards were used and came from: i) the center-West Argentina (MsoilAR4.3), ii) the south of Australia (M224B), iii) the south-west of France (EF3.5(2)) and iv) the west of Germany (EF047). Greenhouse experiments were conducted to assess the association between M. robertsii and potted non-grafted grapevines. First, the comparison of the kinetic of grapevine rhizosphere and endosphere colonization was made, comparing the strain EF3.5(2) with a laboratory strain non-native to the vineyard (ARSEF-2575-GFP) to evaluate if a vineyard-native strain had a more durable colonization. Droplet Digital PCR (ddPCR), a culture-based method, and confocal imaging of root segments were used to characterize the associations. The strain EF3.5(2) had a higher establishment in the rhizosphere and root-endosphere of non-grafted grapevine than the strain ARSEF-2575-GFP. Both strains were established for up to 96-98 days post-inoculation (dpi) in both compartments. Then, the potential of association with the non-grafted grapevine of all four-vineyard native M. robertsii strains was compared. The rates of rhizospheric colonization at 68-70 dpi ranged from 60% for the Argentinian MsoilAR4.3 strain, 65% for the Australian M224B strain, 76% for the French EF3.5(2) strain, to 100% for the German EF047 strain. The rates of root endosphere colonization were 14%, 10%, 5%, and 33% at 68-70 dpi, respectively. No significant differences of rhizosphere and root-endosphere colonization between tested strains were recorded. Also, the fungal association unaffected the grapevine's growth and leaf pigment content during the experimental period. Finally, the effect of direct parasitism of the strain EF3.5(2) on the survival and development of radicicole grape phylloxera clone 'Pcr7' was evaluated in the woody root section bioassay. Depending on the method used to infect the insect, a significant reduction of 90 %, 70 %, and 86% in survival probability was found, and 92%, 89%, and 93 % in reduction of adults' development compared with control treatments. Also, the symptoms induced by grape phylloxera on non-grafted grapevines co-inoculated with M. robertsii were reduced by 91% (mean of 4.8 ± 8.4 nodosities) compared with the phylloxera infested-plants (mean of 52.7 ± 50.7 nodosities). The qPCR analysis performed on grapevine inoculated with strain EF3.5(2) showed after 24h, the up-regulation of the VvWRKY-75, VvPR3.2, VvPR4, and VvG1, which are phylloxera-responsive defense genes involved in the resistance against phylloxera.In conclusion, M. robertsii’s persistent association with non-grafted grapevine represents an alternative protection strategy against radicicole grape phylloxera, especially for wine-growing regions planted with non-grafted vines. Further field experiments should be carried out to determine the environmental factors affecting the effectiveness and persistence of M. robertsii associated with grapevine.