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  • Author or Editor: G.S. Howell x
  • Journal of the American Society for Horticultural Science x
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Abstract

Cold resistance of primary buds from grapevines (Vitis spp.) decreased with advancing phenological development. Morphological characteristics of canes produced during previous growing season had no effect on bud hardiness at a given stage of development or on development rate when cuttings were forced in the greenhouse. Cultivar differences were found to affect both the rate of bud development and the hardiness at a given stage of buds forced from stored cuttings.

Open Access

Abstract

Flower bud hardiness of seven commercial highbush blueberry cultivars (Vaccinium australe Small) was determined from fall to spring for two consecutive years. Hardiness was expressed as T50, estimated by Spearman-Kärber equations. The T50 values for cultivars showed good agreement with spring field survival. Distal buds were less hardy than proximal buds on the same twig. The Average Exotherm (AET) methods were more variable than the T50 method for determining flower bud hardiness.

Open Access
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Abstract

The relationship of environmental temperature to the cold resistance of apple bark tissue was studied on mature orchard trees in the field during natural spring dehardening and on 3 and 4 year old trees in the containers which were dehardened under controlled conditions. Field studies showed day to day fluctuations in dehardening and rehardening during the spring in each of 2 years. These short term changes in cold resistance were closely related to the air temperatures of the preceding day. In controlled studies, hardy plants during the winter dehardened as much as 15°C in one day in a warm greenhouse, and rehardened 15° in 3 days when they were held at −15°. The dehardening process was only partially reversible. Once dehardening began, the bark did not reharden beyond a certain base level. This base level raised with each successive day of dehardening. The base level usually corresponded to the minimum killing temperature on the day preceding the final day of dehardening.

Open Access

Abstract

The reliability and convenience of 5 viability tests were evaluated. Growth and tissue browning were the most reliable tests, but they required considerable time and were qualitative. Triphenyl tetrazolium chloride (TTC) reduction and specific conductivity were satisfactory for grape, but TTC was not as reliable as specific conductivity for cherry and raspberry. Neither test proved satisfactory for strawberry.

A second exotherm always indicated living stems and the absence of a second exotherm accurately predicted stem death. Freezing curves for raspberry showed the stems to be 5 degrees hardier than the control growth tests indicated.

Open Access

Abstract

Open-pollinated progeny from 15 peach (Prunus persica) cultivars, two peach × P. kansuensis hybrids, and one peach almond (P. amygdalus) hybrid were evaluated for their cold hardiness and for tolerance to Cytospora canker following artificial inoculation with Leucostoma persoonii. Winter hardiness was negatively correlated with canker necrotic length (r = −0.26**) and positively correlated with canker rating (r = 0.26**), as indicated by qualitative ratings. The half-sib families differed for canker necrotic length following fall inoculation, indicating that individuals with increased tolerance to L. persoonii canker could be selected from the population. Progeny from the cultivar Yennoh exhibited the shortest canker necrotic length following fall inoculation, and all the inoculated branches were visually healthy. ‘Yennoh’, a plant introduction from Russia, may have a higher tolerance to Leucostoma than has previously been found in U.S. germplasm.

Open Access

Abstract

Application of (2-chloroethyl)phosphonic acid (ethephon) reduced fruit removal force (FRF) as much as 50% depending on concentration and time of application. Reduction in FRF allowed reduced mechanical harvesting vibration frequency which reduced damage to berries during harvest and thus increased shelf-life. Mechanical harvest was further facilitated by ethephon-induced color development and hastening of abscission which reduced the number of machine harvests required.

Open Access