Comparison of conventional and molecular detection methods of Rosellinia necatrix in avocado orchards in southern Spain

White root rot, caused byRosellinia necatrix, is one of the most important diseases in avocado orchards and isparticularly widespread on the Mediterranean seaboard of southern Spain. In this study, the presence of the pathogen insoil samples collected from the base of 47 plants showing different symptoms of canopy decline was assessed with amolecular detection method based on real-time Scorpion PCR. Results were compared with symptoms in the canopy andwith the traditional method of isolation ofR. necatrixfrom roots and/or bark. The fungus was isolated from 24 samplesby the traditional method and from 37 soil samples by the molecular method (cycle threshold values 25·8 to 47·1),demonstrating the higher sensitivity and reliability of the molecular method. A single real-time PCR amplificationwas sufficient to detectR. necatrixin naturally infested soils. The avoidance of nested PCR has important practicalimplications because of the reduced costs and risk of cross contamination. Also, it enables faster sample analysis and ismore appropriate for quantitative detection. A modified molecular method was also developed to detectR. necatrixin roots and in soils with very low populations of the pathogen.