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  • Author or Editor: H.Y Ju x
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To determine the effects of rootstock and frameworking on hardiness, `Gravenstein' apple, which is not winter hardy, was grafted on trees frameworked with the hardy genotypes `Budagovsky 9' (B. 9), `Lobo', Kentville Stock Clone (KSC 28), or `Dudley', all of which were propagated on either `Beautiful Arcade' (BA) seedlings or on `Alnarp 2' (A. 2) rootstocks. For comparison, `Dudley' was grafted on `Dudley' frames propagated on both rootstocks. Growth after 8 years was greatest at Kentville; `Gravenstein' was larger than `Dudley', although when grafted, it was 40% smaller on the dwarf B. 9 than on the `Lobo' frame. On one night in Feb. 1993, all sites recorded temperatures below –30 °C. Blackheart was therefore measured in the rootstock trunk, framebuilder, and scion to document the resistance to this sublethal winter injury. Trees at the two colder sites, Truro and Centreville, had more blackheart than did those at the milder site. The percentage of blackheart in the trunk and frame was greatest for B. 9 and least for KSC 28. The tender scion, `Gravenstein', exhibited extensive blackheart regardless of site, rootstock, or the hardiness of the frame. The hardy scion, `Dudley', had some blackheart in the colder locations but none at Kentville. Blackheart levels in `Gravenstein' were very high on the framebuilder B. 9, and while generally less with the other hardy framebuilders, they were still high. While the hardy frames may have helped improve the survival of this cultivar, they did not change its hardiness status relative to `Dudley', even when `Dudley' was one of the hardy framebuilders.

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Apple trees of the tender cultivar Gravenstein were grown on four promising, dwarfing, stembuilders and two known hardy rootstocks to evaluate hardiness. After eight growing seasons and a “test winter” from 1992 to 1993, trees were subjected to a destructive harvest to assess the amount of blackheart. The extent of blackheart was used as an indicator of sublethal winter injury. The amount of blackheart in the stembuilder trunk was significantly different among stembuilders but not between rootstocks. The stembuilder Bud 9 had more blackheart than Dudley, Lobo, KSC 28, and Ungrafted (Dudley). Similarly, the percentage of blackheart in the scion part of the tree showed differences due to cultivars and stembuilders but no difference due to rootstocks.

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Ginseng seedlings were inoculated with Phytopthora cactorum by dipping their roots for 5 min in a suspension of 105 zoospores/ml. Inoculated plants were repotted and grown under shade in the greenhouse. In various experiments, fungicides were applied 1 week before inoculation, at the time of inoculation, 2 days after inoculation, or a combination of the first two of these. Treatments included fosetyl-Al applied as a foliar spray until run-off at a concentration of 2.5, 5.0, or 10 g a.i./liter of water or as a soil drench containing 0.25, 0.5, or 1.0 g a.i./100 ml water per plant and metalaxyl applied as a soil drench containing 5 or 10 mg a.i./100 ml of water per plant. The treatments with fosetyl-Al as a spray did not reduce root rot ratings, but fosetyl-Al applied as a drench significantly reduced root rot ratings at all three concentrations when applied at inoculation. The best control was achieved using metalaxyl at either 5 or 10 mg a.i./plant applied either at inoculation or both 1 week before inoculation and at inoculation.

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