Limited asymptomatic colonisation of apple tree shoots by Neonectria ditissima following infection of leaf scars and pruning wounds. / Olivieri, Leone; Saville, Robert; Gange, Alan; Xu, Xiangming.

In: Plant Pathology, 06.06.2021.

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European apple canker, caused by Neonectria ditissima, is an important disease of apple (Malus domestica). The fungus may reside asymptomatically in the tree for up to a few years, thus making canker control difficult. Asymptomatic infections established in the nursery can result in severe canker outbreaks in newly established apple orchards. It has been suggested that N. ditissima might colonise the tree beyond the infection point during the asymptomatic stage.
We investigated whether N. ditissima can colonise the internal tissues of apple shoots, both prior to and after visual symptoms. Apple trees were artificially inoculated via pruning wounds and leaf scars; then the pathogen was tracked at the inoculation point and beyond with isolation or real time qPCR. Before visual symptoms, N. ditissima could be detected in the infected pruning cut or leaf scar, but not at a distance of 10-15 mm from the entry point, or greater. Conversely, after symptom expression the pathogen could be detected in the asymptomatic tissue at 10-15 mm from a canker lesion.
This study demonstrated that N. ditissima asymptomatic infection can be detected using real time qPCR and that the pathogen does not grow systemically much further beyond the initial entry point inside the plant before visual canker symptoms appear.
Original languageEnglish
JournalPlant Pathology
Publication statusAccepted/In press - 6 Jun 2021

ID: 42345228