Andrea Podavkova
Overingeniør
(+47) 414 99 474
andrea.podavkova@nibio.no
Sted
Ullensvang
Besøksadresse
Ullensvangvegen 1005, 5781 Lofthus
Forfattere
Dalphy Ondine Camira Harteveld Abdelhameed Elameen Simo Maduna Adam Vivian-Smith Andrea Podavkova Sabine Oettl Stefanie Maria Primisser Jorunn BørveSammendrag
Small, superficial rot spots occurring around lenticels postharvest on apple in Norway have not been identified but were assumed to be underdeveloped Neofabraea lesions. Fungal isolation from such spots on fruit from the 2022 season revealed both Neofabraea perennans and Ramularia spp., identified by B-tubulin and ITS sequencing, respectively. In the 2023 season, isolations were made from fruit with spots resembling dry lenticel spot caused by Ramularia mali. The aim of this study was to identify the Ramularia species associated with the postharvest fruit spots in Norway. Multiple gene regions of five Norwegian isolates (E20, E21 from 2022; 13,15 and 18 from 2023) and three reference isolates, R. mali, R. eucalypti, and R. collo-cygni, were sequenced and used for phylogenetic analysis. The Norwegian isolates were distinct from the included reference isolates, but clustered with other Ramularia species. Isolates 13, 18 and E21 clustered with Ramularia vizellae, while isolates 15 and E20 were most closely related to Ramularia phacae-frigidae. Isolate E20 was sequenced using the Oxford Nanopore Technologies MinION platform. Pathogenicity was assessed in a field inoculation study using isolate E21, resulting in typical spot development on inoculated fruit. Ramularia vizellae has previously been reported from dead apple leaf litter and other woody hosts in the Netherlands and Iran, while R. phacae-frigidae was originally described from Phaca frigida in Switzerland. Neither species has previously been reported in association with apple fruit spotting. While Ramularia mali has caused outbreaks on apple in several European countries, recent studies hypothesize that the symptoms may be caused by a species complex with regional variation. The present results identify candidate species contributing to this complex in Norway and highlight the need for further studies to improve species delimitation and pathogenicity.
Sammendrag
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Sammendrag
Ascospore release by the European apple canker fungus Neonectria ditissima was examined by means of continuously running spore traps mounted over detached segments of apple tree branches with cankers habouring maturing and ripe perithecia, or placed within tree rows in apple orchards. Records began in autumn 2017 and continued for nearly 3 years at two locations in Norway, and for five autumn to late spring periods at two locations in the Lower Elbe region of northern Germany. In northern Germany, the first ascospore releases were recorded during or after autumnal leaf fall, whilst major peaks occurred from March to May. In Norway spore discharge began in spring with a major peak, continued through the summer and autumn, and paused in mid-winter. These observations indicate that in northern Germany, ascospores are less likely to contribute to fruit and leaf scar infections than in Norway. Furthermore, ascospore discharge events in spring, which were recorded in all sampling years at all sites, were associated with the same rain events as those of the apple scab fungus Venturia inaequalis, and would have been covered by intensive fungicide sprays. For northern Germany, these results indicate a shift in major ascospore release peaks from autumn towards spring as compared to previous data collected some 50 years ago.