PCR-based strategy to detect and identify species of Phaeoacremonium causing grapevine diseases.

Species of Phaeoacremonium (especially Phaeoacremonium aleophilum) are associated with two severe diseases in grapevines, Petri disease in young plants and Esca disease in adult plants. Phaeoacremonium species grow slowly on culture medium, and it is difficult to identify these species on the basis of morphological characteristics. Primers Pm1 and Pm2 were designed in the ribosomal DNA internal transcribed spacer (ITS) regions ITS1 and ITS2, respectively. They yielded a single amplicon of 415 bp for nine species of Phaeoacremonium that may occur in grapevines. A nested PCR (using general fungal primers ITS1F/ITS4 in the primary reaction) was developed to detect Phaeoacremonium directly in grapevine wood. Molecular detection was more sensitive than the traditional method of culturing in growth medium was. Identification of Phaeoacremonium species was achieved by digesting the PCR-amplified fragment with the restriction enzymes BssKI, EcoO109I, and HhaI. It was possible to distinguish these species by their restriction fragment length polymorphism patterns, except for Phaeoacremonium viticola and Phaeoacremonium angustius, which had 100% similarity in their ITS region sequences. A species-specific PCR amplification of the partial beta-tubulin gene using the primer pair Pbr4_1/T1 and Pbr8/T1 was necessary to differentiate P. angustius from P. viticola, respectively. An easy and fast protocol was developed to detect and identify species of Phaeoacremonium in a few hours. Primers defined here can be used in a plant nursery sanitation program to produce plants free of Phaeoacremonium spp. Use of healthy grapevine plants in new plantations is the most effective measure to manage Petri disease.