Effect of freezing of &lt;i&gt;Neonectria ditissima&lt;/i&gt; inoculum on its pathogenicity

Scheper, R.W.A.; Frijters, L.; Fisher, B.M.; Hedderley, Duncan I.

doi:10.30843/nzpp.2015.68.5800

Cited by 13 publications

(19 citation statements)

References 14 publications

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“…Inoculum that had been frozen for 462 days, and which had been thawed and re-frozen twice (treatment 52), still resulted in 100% canker expression in both 'Braeburn' and 'Royal Gala' cultivars despite having only 6% germination. Scheper et al (2015) found that the viability of N. ditissima spores suspended in Tween® water was not affected by freezing at -20 o C for a short period of 3 days and the results of the current study are consistent with this earlier work. However, results from recent work (2018) showed that germination of N. ditissima conidia decreased more rapidly (from 84 to 0% in an 8-week period) if they were stored frozen in a mixture of the surfactant Tween® (0.05%) and…”

Section: Discussionsupporting

confidence: 92%

Long-term deep-freeze storage of Neonectria ditissima conidium suspensions does not reduce their ability to infect apple trees

Orchard

Campbell

Turner

et al. 2018

NZPP

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Fresh, wild-type conidium suspensions of Neonectria ditissima prepared from sporulating European canker lesions for use in field inoculation trials are not always readily available. The effect of freezing inoculum on the viability of spores and their ability to cause infection in situ was assessed using 15—19 frozen N. ditissima conidium suspensions during 2015—2017. Freshly prepared inoculum and water only were used to inoculate rasp wounds on ‘Braeburn’ (2015), ‘Scilate’/Envyâ„¢ (2016) and ‘Royal Gala’ and ‘Braeburn’ (2017) along with frozen inoculum ranging in age from 1—462 days at concentrations >104 conidia/mL. Lesion development was assessed at approximately monthly intervals. In all experiments, there was no substantial effect of storage time on lesion development although germination in droplets may have decreased during storage. As expected, there was a cultivar effect (2017 data only), with fewer lesions on ‘Braeburn’ compared with ‘Royal Gala’. Long-term deep-freeze storage up to 462 days of N. ditissima conidium suspensions (>104 conidia/mL) did not affect the ability of spores to infect apple trees. Therefore, spore suspensions can be batch-prepared and stored frozen for future experimental use.

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Section: Discussionsupporting

confidence: 92%

Long-term deep-freeze storage of Neonectria ditissima conidium suspensions does not reduce their ability to infect apple trees

Orchard

Campbell

Turner

et al. 2018

NZPP

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“…The conidia were similar to field-collected conidia, with >75% of the conidia multi-celled and only 5% single-celled. The suspension was frozen at -20˚C for 1 week (Scheper et al 2015).…”

Section: Trial Design and Inoculationmentioning

confidence: 99%

Detached shoot treatments cannot replace whole-tree assays when phenotyping for apple resistance to Neonectria ditissima

Scheper¹,

Fisher²,

Taylor³

et al. 2018

NZPP

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To develop a fast phenotyping method for European canker resistance of apple, detached-shoot assays were compared with whole-tree phenotyping methods. Disease incidence and lesion length in detached shoots and potted trees of six apple accessions were compared after inoculation with Neonectria ditissima conidia in a glasshouse. Detached shoots were placed in aerated water or in a Chrysal solution, with and without water changes. ‘Royal Gala’ trees had the highest disease incidence (90%) and ‘Robusta 5’ trees remained lesion-free. The treatment-accession interaction effect was significant, with higher disease incidence in detached shoots of ‘Robusta 5’ (4—32%) than ‘Braeburn’ (0—2%), while ‘Braeburn’ trees had a high disease incidence (64%). ‘Robusta 5’ had smaller lesions than the other accessions, but significant differences between accessions were observed on only one of three assessment dates. None of the detached-shoot assays resulted in a similar ranking of the accessions compared with the potted-tree assay, using disease incidence or lesion length. Detached-shoot treatments cannot replace whole-tree assays when phenotyping for European canker resistance of apple.

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“…To facilitate infection with low-virulent isolates, the known susceptible apple accession 'Royal Gala' was chosen (Scheper et al 2015;Amponsah et al 2017;Scheper et al 2018). Similarly, rasp wounds were used to optimise the chance of infection with low-virulent isolates, as larger wounds lead to shorter incubation periods and higher infection rates (Walter et al 2016).…”

Section: Apple Host and Wound Selectionmentioning

confidence: 99%

“…Conversely, the N. ditissima population varies in virulence on the apple host (Scheper et al 2015) and conidial morphology (Scheper et al 2014). Similarly, differential host-pathogen interactions in the Malus-N. ditissima pathosystem have been observed (Scheper et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Successive passaging through an apple host of six low-virulent <i>Neonectria ditissima </i>isolates increased virulence in one of them

Scheper

Fisher

Bowen

et al. 2019

NZPP

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Neonectria ditissima is a serious pathogen of apple. Low-virulent cultures of this fungus have been isolated from cankers, but how and why low-virulent isolates can infect apple is unknown. Rasp wounds on ‘Royal Gala’ trees were inoculated with agar plugs from six low-virulent N. ditissima isolates in a glasshouse. Neonectria ditissima was re-isolated 10 weeks after inoculation. Agar plugs from the re-isolated cultures were used to inoculate ‘Royal Gala’ trees again. After the second re-isolation, conidial suspensions of the original cultures and the 2 x 6 re-isolates were used to determine the virulence on ‘Royal Gala’ compared with field-collected conidia. Three cultures did not cause any lesions; neither did their re-isolates. The re-isolates of two cultures did not differ in virulence compared with the originals. However, the virulence of one isolate increased with each re-isolation, with the second re-isolation causing significantly more lesions, lesion development occurring faster and the lesions being larger than those caused by the original isolate. Therefore, the virulence of N. ditissima isolates can change over time, with loss or gain possibly being attributed to epigenetic and/or genetic changes in the genome.

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Effect of freezing of <i>Neonectria ditissima</i> inoculum on its pathogenicity

Cited by 13 publications

References 14 publications

Long-term deep-freeze storage of Neonectria ditissima conidium suspensions does not reduce their ability to infect apple trees

Long-term deep-freeze storage of Neonectria ditissima conidium suspensions does not reduce their ability to infect apple trees

Detached shoot treatments cannot replace whole-tree assays when phenotyping for apple resistance to Neonectria ditissima

Successive passaging through an apple host of six low-virulent <i>Neonectria ditissima </i>isolates increased virulence in one of them

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