Search Results
The relationship between yield and applied N in cranberry has been investigated. Cultivar was important in determining optimum seasonal N rate. Sustained production for the hybrid `Stevens' required an annual seasonal total of N at up to 67 kg·ha–1, higher than was optimal for native selections `Early Black' and `Howes'. High N rates were associated with increased fruit rot and vine overgrowth. Optimum N rate varied within cultivar, likely due to variation in soil conditions, but soil N test results have not correlated well with subsequent yield in cranberry. Soil organic matter content can predict potential N release, but plant response must also be taken into account. To refine N rate recommendations, plant characteristics that might predict N requirements/status of cranberry were investigated. A standard of 0.9% to 1.1% N in August tissue has been established for cranberry. To find characteristics that could be used earlier, we surveyed 30 sites for percentage of N in tissue, length of new growth, SPAD chlorophyll meter ratings, fertilizer N use, and yield. Length of new growth could be used as an indicator of cranberry N status from June until bloom, being positively correlated with subsequent yield. The SPAD meter proved to be a viable alternative to in-season monitoring of tissue N during June and July. Readings below proposed standard values indicated the need for N fertilizer if vegetative growth was in the standard range. Thus, the easily determined factors of upright length and SPAD rating could be used to refine fertilizer rates during the active growing season, while tissue testing for percentage of N could be used as a “report card” on the fertilizer program at the end of the season.
The application of ultraviolet light on fruit and vegetables is a promising new method to control storage diseases and to delay the onset of senescence. In this investigation, we studied the effects of hormic dose (1,4 Merg•cm-2) of UV-radiation on the ripening of tomato pericarp discs by measuring different characteristics of ripening and senescence during storage. We observed that UV-treatment induced significant delays of the red color development, chlorophyll degradation, and lycopene production compared to control discs. UV-treatment also retarded the decline of the chlorophyll-a fluorescence ratios Fv: Fm and *F : Fm′, two characteristics related, respectively, to the maximum and operational quantum yield of photosystem II electron transport. Furthermore, the climacteric ethylene peak was delayed in the treated discs. However, UV-treatment did not alter textural changes, and the respiratory climacteric peaks were observed concomitantly for both treated and untreated tomato discs. However, the respiratory rate was consistently higher in treated discs. These results indicate that UV irradiation of tomato pericarp discs delays some processes of ripening associated with chloroplast to chromoplast transition whereas other ripening processes seem unaffected.
Ornamental flowering cherry trees (Prunus species) are popular landscape plants that are used in residential and commercial landscapes throughout most temperate regions of the world. Most of the flowering cherry trees planted in the United States represent relatively few species. The U.S. National Arboretum has an ongoing breeding program aimed at broadening this base by developing new cultivars of ornamental cherry with disease and pest resistance, tolerance to environmental stresses, and superior ornamental characteristics. Knowledge of the genetic relationships among species would be useful in breeding and germplasm conservation efforts. However, the taxonomy of flowering cherry species and cultivars is complicated by differences in ploidy levels and intercrossing among species. We have used simple sequence repeat (SSR) markers developed for other Prunus species to screen a diverse collection of over 200 ornamental cherry genotypes representing 70 taxa in order to determine the genetic relationships among species, cultivars, and accessions. Data were generated from 9–12 primer pairs using an automated DNA genetic analyzer (ABI3770), and subjected to UPGMA cluster analysis. Extremely high levels of polymorphism were exhibited among the materials studied, thus indicating that ornamental flowering cherry germplasm has substantial inherent genetic diversity. This information, combined with traditional morphological characteristics, will be useful in determining genetic relationships among accessions in our collection and for predicting crossability of taxa.
Twelve early to midseason ripening tomato cultivars were evaluated for early and total marketable yield, fruit size, and external characteristics under the cool, short growing season of northern New England. The acceptability of external and internal color, texture, and flavor of four cultivars was evaluated by a sensory panel of 50 members. There was little difference between cultivars in total yield. This was probably due to an early frost that destroyed much of the later ripening fruit. `Summerset' had the highest early and overall yields but the smallest fruit size. `Johnny's 361` had high overall yield and large fruit with good early yields. `Pilgrim' had high early yield, good overall yield, and fair fruit size. `Jetstar' and `Daybreak' fell into the middle of the range for total yield and fruit size, but `Jetstar' had very low early yield. `Pik Red' and `Pik Rite' had low early and total yields but good fruit size. `Moreton Hybrid' had fair early and total yields and small fruit size. In the sensory analysis, `Sunrise' had the highest rated external color, while `Moreton Hybrid' had the lowest rating. Internal color ratings did not vary greatly, although `Sunrise' was least acceptable in this characteristic. `Jetstar' was rated highest for flavor and texture, followed by `Moreton Hybrid', `Sunrise', and `Valley Girl'.
Postproduction characteristics of the new poinsettia cultivar `Freedom', as influenced by production and postproduction treatments, were evaluated. In one study, plants were grown under three production irradiance levels consisting of 450, 675 or 900 μmol s-1m-2 at 18/24C or 22/28C night/day temperatures and moved at anthesis to postproduction conditions (10 μmol s-1m-2 for 12 hr/day, 21±2C). Anthesis was delayed, plant height and diameter decreased, and a reduction in the number and development of cyathia occurred when maintained at low production temperature and irradiance. Leaf drop, which was minimal after 30 days postproduction (< 25%), was unaffected by production treatments, while cyathia drop was accelerated by low production irradiance and temperature, but not reduced after 30 days.
Leaf retention and quality in postproduction conditions are excellent. Cyathia drop averages 40 to 50% after 2 weeks in postproduction conditions. Bracts and leaves maintain their color well, with only slight fading after 30 days. Plants exhibit slight epinasty after shipping, but recover within a couple of days. These characteristics of `Freedom' make it a promising variety for the future.
Most of the works evaluating dormancy completion relies on measuring the level of budbreaking or the time needed for buds to break in forcing conditions. In all cases, the evaluation of budbreak is limited to the initial stages of bud opening in both vegetative and floral buds. Very rarely the response of the new growth is determined. It is accepted that dormancy completion of the bud is of a qualitative nature of yes or no. This reasoning led to using excised branches that can not support normally a growing bud but may support the evaluation of the emerging buds. In practice, the effect of breaking bud dormancy is far reaching and has an impact on the development after budbreaking. Growth vigor is a characteristic tied to the rate of dormancy completion in a quantitative manner. After exposure to sufficient chilling growth is rapid and vigorous. When buds are exposed to warm winters, growth is sluggish and poor. Under certain conditions, budbreak may be high, but all vegetative buds will form rosettes. Likewise with floral buds, they may break satisfactorily but will not set normal fruit especially in stone fruit species. In a recent study of bud dormancy inheritance in apricots, budbreak showed a clear dominance of the low chilling characteristic; level of vegetative vigor showed a similar effect to the high and low chilling parents. Thus, two characteristics of dormancy completion should be considered. The first is the level of budbreak and the other is the vigor of the growing vegetative buds and the functionality of the flower buds, as both are affected by the conditions that induce dormancy completion.
Aruncus `Misty Lace is a new hybrid selection between Aruncus dioicus and A. aethusifolius. The plants outstanding characteristics include heat tolerance, dwarf stature, and delicate, plume-like flowers. The objectives of this study were to evaluate the effect of different production parameters (chilling duration, container size, and photoperiod) on flowering in this new genotype Tissue cultured plantlets of Aruncus `Misty Lace' were transplanted to 72- or 36-cell trays and to 10-cm pots. Transplanted materials remained on the greenhouse bench until roots were visible in the soil plug, then placed in a cooler at 2-4 °C for 0 (control), 4, 6, 8, 10 and 12 weeks of chilling. Upon removal, plants were placed in a greenhouse in 10-cm containers under long or short day photoperiods until flowering, or until the experiment was terminated. Plants required less time on the bench to flower as cooling time increased, regardless of container size. Plants flowered earlier under long days than short days, but photoperiod was less of a factor in the control of flowering than cooling duration. Death of plants was greatest in the 72-plug cells and least in 10-cm pots. Plants without well established root growth sustained significant losses, regardless of container size.
The nutrient uptake kinetics by new roots of 1-year-old potted clonal apple rootstocks (M7, M9, M26, M27, MM106, and MM111) were determined by the ion depletion technique at the stable development stage of trees in August. The total roots of five of the rootstocks (except MM111) consisted of more than 60% feeder roots and less than 12% extension roots. MM111, the most vigorous rootstocks tested, had 60.7% feeder roots and 24.5% extension roots. Root: top ratio was negatively related to the growth inhibiting character of the rootstock. Nutrient uptake by excised new roots was found to fit into Michaelis-Menton kinetic model for all rootstocks tested. The kinetic characteristics (maximum uptake rate, Imax, apparent Michaelis-Menton constant, Km, and root absorption power, (α = Imax•1/Km) between rootstocks differed significantly. MM111 had the highest Imax for NH4 + absorption and M9 for NO3 -. Root affinity to ions was highest with MM106 for NH4 + and with M26 for NO3 -. Root absorption power (α = Imax•1/Km) was greatest in MM106 for NH4 + and M9 for NO3 -. At this developmental stage the data suggest no relationship between nutrient uptake and dwarfing character of the rootstocks.
Flowering and fruit set characteristics were examined in the popular commercial cultivar Magaoa in an effort to elucidate the reproductive phenology of mamey sapote, Calocarpum sapota (Jacq.) Merr. [syn. Pouteria sapota (Jacq.) H.E. Moore and Stearn]. Flowers opened during the night with anthesis beginning around sunset. The length of floral opening varied according to season, ranging from 6 days in winter to a single day in summer. Bursts of new flowers generally appeared in cycles of about 7 days in declining numbers of flowers per burst until all the floral buds of a particular floral bud flush had flowered. Floral buds flowered randomly along a branch with only a few flowers open at any one time. Flower position around the branch was a factor in fruit set. Flowers and small fruitlets encircled horizontal branches in great numbers, but immature fruit most often developed from flowers located on the upper branch quadrant. The lower quadrant contained the fewest immature fruit. As fruit matured, however, more upper quadrant fruit abscised until by harvest, most mature fruit were found on the lower quadrant. The observations provide new insights into the reproductive phenology of mamey sapote.
New cultivars, `SKK 1' and `SKK 2', of Korean mountain ash (Sorbus alnifolia) that had superior morphological features as woody landscape plants were selected from 5000 seedlings of Sorbus alnifolia. Two clones with genetic variation were selected from 1983 to 1994 as landscape plants with large leaf and unique tree form: `SKK 1', which had large leaf and flower, and `SKK 2', with semi-weeping tree form. New selected cultivars of S. alnifolia were successfully grafted and inherited their mother characteristics. Sorbus alnifolia was difficult to propagate by cutting. Therefore, in vitro propagation methods might be used to propagate the superior cultivars. Shoots with apical and axillary buds were excised from 1-year-old seedlings. The explants were cultured on WPM supplemented with 0.5 mg/L BA. Shoots formed from initial cultures were subcultured at ≈4-week intervals onto the same media. To know the best hormone concentration in shoot multiplication, 0.1–3.0 mg/L of BA and 0.1–1.0 mg/L of zeatin were added to each WPM and MS media. The best shoot proliferation and elongation were obtained on MS medium with 1.0 mg/L BA from the whole shoot with the callus-like tissue, whereas the worst results were obtained from shoot tip. A 13-fold proliferation rate was achieved every 4 weeks.