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  • Author or Editor: R. Marini x
  • Journal of the American Society for Horticultural Science x
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Abstract

Peach [Prunus persica (L.) Batsch cv. Harken] fruit were harvested at the firm-mature stage on 5 different dates. Fruit of uniform size were sampled randomly on each date from each of 4 quadrants per tree and evaluated for color, firmness, and soluble solids using the red and green sides of each fruit. A statistical model was used to identify and separate the sources of within- and among-tree variation in fruit quality indices. All quality indices were affected by harvest date. Fruit- and tree-related interactions accounted for a major part of the total random variation. Variance estimates were used to determine numbers of trees per treatment and fruit per tree needed to detect fruit quality differences of a desired magnitude. In general, 6 trees per treatment and 12 to 16 fruit per tree could be expected to detect meaningful differences in fruit quality in experiments involving 2 treatments.

Open Access
Authors: and

Abstract

The viability of freeze-stressed Fragaria × ananassa Duch. cv. Catskill strawberry crown tissues was evaluated using triphenyl tetrazolium chloride (TTC) reduction and oxidative browning. Both tests showed the medulla tissue to be the most susceptible to low-temperature injury, while vascular tissue was least susceptible. TTC reduction appears to be negatively related to tissue browning, and both provide similar results pertaining to tissue viability.

Open Access
Authors: and

Abstract

Strawberry plants (Fragaria × ananassa Duch. cv. Catskill) were subjected to several freezing temperatures to study growth and development following various degress of crown injury. The T50 was approximately —l2.5°C, but exposure to nonlethal temperatures resulted in abnormal growth of leaves, early runner production, decreased blossom numbers, and browning of crown tissues. Browning of crown tissues was associated with number of runners, number of blossoms, size of leaves, dry wt of leaves, and test temperatures. Number of blossoms emerging was negatively correlated with low freezing temperature, while early runner emergence was positively correlated with low temperature.

Open Access

The effect of nighttime ozone (O3) exposure, alone and in combination with daytime O3 treatment, was tested on yield of an O3-resistant (R123) and an O3-sensitive (S156) snap bean (Phaseolus vulgaris L.) genotype. Three trials, with exposure durations ranging in length from 14 to 21 days, were conducted in continuous stirred tank reactors located within a greenhouse. The effects of day-only (0800–1900 hr = 11 hours·day−1) and day + night (0800–1900 hr + 2000–0700 hr = 22 hours·day−1) exposure timings were compared. The Fall 2014 trial also tested the effect of nighttime-only (2000–0700 hr = 11 hours·day−1) O3 exposure. Nighttime O3 exposure alone, at 62 ppb, did not cause foliar injury and had no effect on the yield of either genotype. In combination with daytime O3 exposure, nighttime O3 concentrations up to 78 ppb did not impact yields or show a consistent effect on nocturnal stomatal conductance (g sn). When data were pooled across the day and day + night exposures times, mean daytime O3 levels ≥62 ppb caused foliar injury and significant yield decreases in all three trials. Under control conditions, R123 and S156 produced similar pod masses in two of the three trials. In all three trials, R123 produced significantly greater yields by mass than S156 with elevated O3. Nighttime conductance measurements suggested that S156 and R123 have inherently different g sn rates and that cumulative O3 exposure can increase g sn in both genotypes.

Free access

Effects of nighttime (2000 to 0700 hr) O3 on the pod mass of sensitive (S156) and resistant (R123) snap bean (Phaseolus vulgaris) genotypes were assessed using continuous stirred tank reactors located within a greenhouse. Two concentration-response relationship trials were designed to evaluate yield response to nighttime O3 exposure (10 to 265 ppb) in combination with daytime exposure at background levels (44 and 62 ppb). Three replicated trials tested the impact of nighttime O3 treatment at means of 145, 144, and 145 ppb on yields. In addition, stomatal conductance (g S) measurements documented diurnal variations and assessed the effects of genotype and leaf age. During the concentration-response experiments, pod mass had a significant linear relationship with the nighttime O3 concentration across genotypes. Yield losses of 15% and 50% occurred at nighttime exposure levels of ≈45 and 145 ppb, respectively, for S156, whereas R123 yields decreased by 15% at ≈150 ppb. At low nighttime O3 levels of ≈100 ppb, R123 yields initially increased up to 116% of the treatment that received no added nighttime O3, suggesting a potential hormesis effect for R123, but not for S156. Results from replicated trials revealed significant yield losses in both genotypes following combined day and night exposure, whereas night-only exposure caused significant decreases only for S156. The g S rates ranged from less than 100 mmol·m−2·s−1 in the evening to midday levels more than 1000 mmol·m−2·s−1. At sunrise and sunset, S156 had significantly higher g S rates than R123, suggesting a greater potential O3 flux into leaves. Across genotypes, younger rapidly growing leaves had higher g S rates than mature fully expanded leaves when evaluated at four different times during the day. Although these were long-term trials, g S measurements and observations of foliar injury development suggest that acute injury, occurring at approximately the time of sunrise, also may have contributed to yield losses. To our knowledge, these are the first results to confirm that the relative O3 sensitivity of the S156/R123 genotypes is valid for nighttime exposure.

Open Access