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  • Author or Editor: Soo-Hyung Kim x
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Soil amendment with biochar is thought to confer multiple benefits to plants including induction of systemic resistance to plant pathogens. Pathogens in the genus Phytophthora cause damaging diseases of woody species throughout the world. The objective of this study was to test 1) whether biochar amendment induces resistance to canker causing Phytophthora pathogens; and 2) how this resistance is related to the amount of biochar amendment in two common landscape tree species: Quercus rubra (L.) and Acer rubrum (L.). Seedlings of Q. rubra and A. rubrum were planted in peatmoss-based potting mix uniformly amended with 0%, 5%, 10%, or 20% biochar by volume. Plants in each treatment group were stem wound-inoculated with an isolate of Phytophthora cinnamomi Rands (host: Q. rubra) or P. cactorum (Leb. and Cohn) Schröeter (host: A. rubrum) using standard agar-plug inoculation procedures. Amendment of potting media with 5% biochar reduced horizontal expansion of lesions in both hosts, whereas the same treatment significantly reduced vertical expansion of lesions in A. rubrum (P < 0.05). In addition, 5% biochar resulted in a higher midday stem water potential in Q. rubra (P = 0.066) and significantly greater stem biomass in A. rubrum compared with inoculated control plants (0% biochar, P < 0.05). Our results suggest that biochar amendment has the potential to alleviate disease progression and physiological stress caused by Phytophthora canker pathogens and there is likely an optimal level of biochar incorporation into the root media beyond which the effects may be less pronounced.

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Innovative approaches are required for improving crop productivity and quality to meet the increasing demand for providing food, energy, and other services for growing populations in a changing climate. The colloquium sponsored by the Environmental Stress Physiology (STRS) Working Group at the 2011 American Society for Horticultural Science (ASHS) annual conference served as a forum to bring together several of the emerging methods for diagnosing, monitoring, and mitigating crop environmental stress with an emphasis on horticultural, physiological, and ecological approaches. These methods are likely to be readily applicable for many research areas in specialty crops in the context of climate change. The colloquium articles in this volume provide a foundation and context to lead dialogues and initiate research themes for developing adaptive strategies to minimize climate impacts on horticultural crop production in a changing climate.

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This experiment was carried out to investigate the effective cutting methods and media for hardwood cuttings in `Sunaga Wase' peach (Prunus persica L.). Using 1-year-old peach stems out of winter pruning, the cutting stems were procurred through several steps on 16 Feb. 1995 and 1996. i) Cut 30 cm in length by pruning scissors and bundled to 10 stems; ii) 1-cm bottom part of cutting stem dipped into IBA (1000 ppm solution) for 5 s and then powdering with Captan WP; iii) upper part of cutting stem coated with Topsin paste; iv) standing the bundled cutting stems in the cutting bench filled with cutting media; v) the temperature maintained at 20 ± 1°C under the level of cutting media by bottom heating and at 5 to 10°C above the media level. Among the cutting media, vermiculite showed the highest rooting percentage, as much as 93.2%, followed by Jiffy pot and rockwool cube. High transplanting survival percentage under field conditions was obtained by the treatment of vermiculite of media + cutting duration for 35 days. Although the treatment of cutting duration for 55 days showed very high percentage of rooting, such as 96.4% in vermiculite, 78.3% in Jiffy pots, and 83.3% of rockwool cube, their percentage of nursery survival after transplanting were reduced remarkably less than 10% in nursery fields covered with black polyethylene film. The nursery trees obtained from each treatment were characteristically 136 to 146 cm in tree height and 22.9 to 26.8 cm in trunk diameter.

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In order to investigate the super-density planting in peach orchards, the experiment was carried out using nursery trees out of hardwood cuttings in `Sunaga Wase' peach (Prunus persica L.). The nursery trees were planted with various planting densities of 1 × 0.5 m (20,000 trees/ha), 1 × 1 m (10,000 trees/ha), 2 × 0.5 m (10,000 trees/ha), 2 × 1 m (5,000 trees/ha), and 6 × 5 m (330 trees/ha) as traditional density on 22 Mar. 1995. As soon as fruit harvest in mid-July, the peach trees were pruned by thinning and heading-back the shoots to induce the new shoot as well as to limit the tree height and lower the canopy. During the second year after planting, nursery cutting trees yielded the most peach fruits from the planting density of 1 × 0.5 m, as much as 14.37 t, which was 14 times higher than the 6 × 5 m of traditional density, followed by 2 × 0.5 m, 1 × 1 m, 2 × 1 m, and 6 × 5 m, respectively. According to summer pruning just after harvest, remaining vegetative buds burst and then the new shoot grew very vigorously in several days. The floral bud differentiation on the new shoots was lower, as much as 32.2%, than that of 77.9% in no-pruning shoots. There were no differences in fruit characteristics among various planting densities.

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