Simultaneous Detection of the Defoliating and Nondefoliating Verticillium dahliae Pathotypes in Infected Olive Plants by Duplex, Nested Polymerase Chain Reaction.

Pathogen-free certified planting material and accurate detection of Verticillium dahliae pathotypes infecting the plant are key components of successful management of Verticillium wilt of olive. Use of a nested-polymerase chain reaction (PCR) procedure developed in earlier studies for in planta detection of the defoliating (D) and nondefoliating (ND) V. dahliae pathotypes resulted in ambiguous detection of the pathogen in some cases, due to heterologous amplification of the D-associated marker in ND-infected olive plants. In the present study, an improved procedure was developed that eliminates ambiguity and reduces time and cost for detection of D and ND V. dahliae in olive. The improved procedure is based on the simultaneous amplification of both an ND- and a new D-specific marker by means of duplex, nested PCR. The procedure was effective in the rapid and unequivocal detection of the D and ND V. dahliae in both artificially inoculated, own-rooted olive plants and naturally infected adult olive trees of different cultivar, age, and growing conditions. Furthermore, the duplex, nested-PCR procedure detected simultaneously the D and ND pathotypes in adult olive trees naturally infected by both pathotypes and in young olive plants that were double-inoculated with D and ND isolates under controlled conditions.