Abstract

Verticillium wilt caused by Verticillium dahliae infects olive at any time point of its life cycle. The severity of verticillium wilt on olive trees depends upon the virulence of the pathogen isolates. Isolates of V. dahliae infecting cotton and olive showed cross virulence, which was classified into defoliating (D) and non-defoliating (ND) pathotypes based on their ability to completely defoliate the plant or only cause wilt (i. e. no defoliation). In recent years, several different types of molecular techniques have been used for identifying V. dahliae isolates in a wide range of hosts or virulence. The polymerase chain reaction (PCR) procedure was used in this study for the detection and quantification of verticillium wilt pathogens. The incidences of V. dahliae on olive in different areas of Iraq and Jordan were investigated. The samples from the same trees were used to detect the type of pathogenic strain [defoliating pathotype (D) versus non-defoliating pathotype (ND)] using PCR with specific primer pairs. The isolates showed positive results using nested PCR reactions, proving the existence of V. dahliae pathogen in tested olive trees in Iraq. The results confirm that the pathotype of V. dahliae is from the ND type. This is the first report which showed the existence of ND V. dahliae in Iraq.