Real-time PCR for rapid in planta detection of Plectosphaerella cucumerina on wild rocket (Diplotaxis tenuifolia)

Abstract

Plectosphaerella cucumerina that has recently been described as causing a leaf spot on wild rocket (Diplotaxis tenuifolia) in Italy, but has not yet been recorded on this host in other countries. This fungus has the potential to cause severe economic losses to the salad-producing industry, especially in Italy. This paper describes the development of a real-time PCR assay based on internal transcribed spacer (ITS) sequence, to aid diagnosis of this pathogen in culture and in plant material. The assay showed no cross reaction with closely related Plectosphaerella species or with 18 other commonly found fungi, and was able to detect 10 fg of Pa. cucumerina DNA per reaction. The assay was more specific than previously available molecular methods. A comparison of molecular and isolation methods indicated that the real-time PCR method is suitable for detection of the pathogen on plant material.