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Limited asymptomatic colonization of apple tree shoots by Neonectria ditissima following infection of leaf scars and pruning wounds
Author(s) -
Olivieri Leone,
Saville Robert J.,
Gange Alan C.,
Xu Xiangming
Publication year - 2021
Publication title -
plant pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.928
H-Index - 85
eISSN - 1365-3059
pISSN - 0032-0862
DOI - 10.1111/ppa.13419
Subject(s) - canker , biology , malus , inoculation , pruning , pathogen , asymptomatic , outbreak , shoot , fruit tree , horticulture , fungus , colonization , botany , microbiology and biotechnology , virology , pathology , medicine
Abstract European apple canker, caused by Neonectria ditissima , is an important disease of apple ( Malus domestica ). The fungus may reside in the tree without causing symptoms 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 colonize the tree beyond the infection point during the asymptomatic stage. We investigated whether N . ditissima can colonize 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 quantitative PCR (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 symptomless tissue at 10–15 mm from a canker lesion. This study demonstrated that the asymptomatic infection by N . ditissima can be detected using qPCR and that the pathogen does not grow systemically much beyond the initial entry point inside the plant before visual canker symptoms appear.