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New Zealand Plant Protection 63 (2010): 280

Comparing methods to determine European canker resistance in apple tree accessions

R.W.A. Scheper and B.M. Fisher


Pruning cuts made in summer, and pruning cuts, leaf scars and score wounds made in autumn were inoculated to compare their suitability to discriminate for European canker resistance among apple accessions. When pruning cuts were inoculated in summer, the mean lesion size varied between accessions, with 'Royal Gala' displaying significantly larger lesions than 15 other accessions, 17 to 43 days after inoculation (P<0.001). 'Robusta 5' (R5) and 'M.9' had the smallest lesions 43 days after inoculation. When pruning cuts were inoculated in autumn, R5 displayed the smallest lesions among 12 accessions, 4 and 10 months after inoculation, while 'M.9', 'Royal Gala' and 'Granny Smith' had significantly larger lesions than R5 (P<0.001). Inoculated score wounds of 'Granny Smith' and 'Jonathan' developed significantly smaller lesions than those of 'M.9' (P<0.001). When leaf scars were inoculated, 'Jonathan' developed symptoms on only 10% of the leaf scars, and lesions were significantly smaller than in other accessions (P<0.001). 'Royal Gala' had the largest lesions, and 56% of leaf scars of 'M.9' developed symptoms. This study has shown that the expression of the disease in various accessions differs according to the method and timing of inoculation.

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