Search Results
Abstract
An effective growth regulator treatment for inducing fruit set and parthenocarpic development in the highbush blueberry would restore a number of once productive varieties to profitable commercial use. The decline in productiveness of varieties such as Coville, Earliblue and Jersey has paralleled the decline in native pollinating insects such as the bumblebee (4). The use of commercial honeybees has not solved the fruit set problem in many cases because the problem varieties appear to be less attractive to the domesticated bees than are the fruitful varieties (4).
Abstract
Gibberellic acid (GA) at 0, 5, 50, 200 and 500 ppm was applied to the highbush blueberry, var. ‘Coville,’ for 3 consecutive fruiting periods in the greenhouse. Application to the flower was a prerequisite for parthenocarpic fruit set and development. No significant differences were found in the number of shoots formed, shoot length, and stem or trunk diameter. GA caused a significant reduction in the number of flower buds formed for the next crop.
Abstract
Gibberellic acid (GA) at 0, 50, 100, 250 and 500 ppm was applied to the highbush blueberry var. ‘Coville’ at bloom for 2 consecutive seasons in the field. Percentage fruit set was increased by all GA treatments in 1966. In 1967 yields were increased by the 100, 500 and 500 ppm caged treatments. GA-treated plants produced smaller berries that required a longer maturation period but were still of fresh market quality. The smallest and latest maturing fruit were seedless and were produced from caged plants receiving GA. No differences in mold incidence and percentage weight loss in storage were apparent between treated fruit and the control. Only fruit from caged plants receiving 500 ppm GA had refractive index values less than those of the control berries. The GA treatments did not reduce the number of flower buds formed in 1966 or 1967.
Abstract
‘Coville’ and ‘Jersey’ blueberry (Vaccinium) flowers and fruit from screened bushes treated with 500 ppm of gibberellic acid (GA) at bloom and from bushes subject to insect pollination were sampled and measured at weekly intervals. Extracts of these organs were partially purified by chromatographic separation on paper, then bioassayed for auxin and gibberellin-like (GA-like) activity. Endogenous levels of both auxin and GA-like substances were higher in ‘Jersey’ than in ‘Coville’ flowers. Auxin concentration in unpollinated flowers was 4 times greater in ‘Jersey’ than in ‘Coville’. A large increase in extractable auxin followed GA treatment in both cultivars. The increase in extractable auxin coincided with the more rapid initial growth rate characteristic of GA-treated fruits. Auxin level coincided with fruit growth rate much better than did level of GA-like substances. By 6 weeks after GA treatment, GA-like substances in the fruits decreased to a level no higher than that in pollinated fruits.
Abstract
Various flower parts were measured from 35 different cultivars and selections of highbush blueberry and correlated to their fruit setting capability. High fruit set was associated with a short distance between stigma and anther tip. The ideal flower from the standpoint of max fruit set appears to be one with a short corolla that widened at the middle to more than 8 mm and then narrowed perceptibly at the base. It is suggested that flower structure might serve the plant breeder as an additional criterion for evaluating the potential fruit setting capability of a blueberry selection.
Abstract
Fourteen highbush blueberry cultivars and selections differed greatly in percentage blue and green fruit removed during a 3 second vibration of individual fruiting shoots with a hand-held vibrator. With cultivars ‘Croatan’, ‘Wolcott’, ‘Morrow’, ‘Murphy’, and ‘Collins’ more than 90% of the blue fruit and less than 15% green fruit were removed. These cultivars have desirable detachment characteristics and required a force of less than 85 g to remove individual blue fruit.
Abstract
(2-Chloroethyl)phosphonic acid (ethephon) plus 0.1% polyoxyethylene sorbitan (Tween 20) was applied as a fruit cluster dip at 2000, 4000, and 8000 ppm to highbush blueberries (Vaccinium corymbosum L. cv. Morrow) at different stages of berry development. Earliest ripening was obtained with 8000 ppm treatment made late in Stage II. Ripening date was not related to concentration when applied in Stage III. Harvest period was shortest, less than 1 week, when treatments were applied in Stage III, regardless of concentration. Berry weight decreased with increased concentration, but little difference was noted with respect to stage of development at time of application. Generally, pH decreased with increasing concentration of ethephon and with advancement in stage of development at time of treatment. An increase in ethephon concentration resulted in an increase in acidity, decrease in soluble solids (SS) and decrease in SS/acid ratio at each time of application until Stage III of fruit development. Stage III treatments showed no concentration effect with the exception of the acidity response to the 8000 ppm treatment. Optimum time of application was near the end of Stage II and the beginning of Stage III.
Abstract
Hexazinone was applied as a soil drench to 1-year-old rooted hardwood cuttings of highbush (Vaccinium corymbosum L.) and rabbiteye (V. ashei Reade) blueberries in a series of greenhouse experiments. No differences in susceptibility to hexazinone were detected among 10 highbush and 3 rabbiteye cultivars growing in a fine sand soil. Two highbush and 2 rabbiteye cultivars were assayed for hexazinone tolerance in low, medium, and high organic matter soil which contained 1.3%, 3.5%, and 49.5% organic matter, respectively. Hexazinone at 1 or 2 kg/ha had no inhibitory effect on blueberry growth in the high organic matter soil, inhibited growth slightly on the medium organic matter soil and caused severe injury in the low organic matter soil. At rates of 4 and 8 kg/ha, injury was severe on the medium and low organic matter soils but very slight on the high organic matter soil.
Abstract
Ericoid mycorrhizae were measured on roots of wild and cultivated highbush blueberries (Vaccinium corymbosum L.) from 7 locations in southeastern North Carolina over 4 sampling dates. An adequate clearing and staining procedure was developed specifically for observing endomycorrhizae in blueberry roots. Abundant mycorrhizae were found in wild blueberry plants, but few mycorrhizae were noted in cultivated plants. Phosphorus levels were lower in the wild than in the cultivated blueberry soils at most locations.