), and beta-carotene content than fruits from plants without receiving any foliar K application ( Lester, 2005 ). In tomato, it has been reported that acid and reducing sugar contents, often correlated with K application, influence not only sweet and
Sofia Caretto, Angelo Parente, Francesco Serio, and Pietro Santamaria
Leah C. McCann and Philipp W. Simon
When stored at temperatures less than 10 °C, tubers of all cultivated potatoes exhibit cold-induced sweetening (CIS) during which starch degrades to sucrose, glucose, and fructose. Upon frying at high temperatures, the reducing sugars (Fru, Glu) interact with free amino acids via the non-enzymatic Maillard reaction to form dark-colored chips that are unacceptable to consumers. In addition, scientists recently discovered that the toxic chemical acrylamide is also produced during frying. Although storage at warmer temperatures reverses CIS and circumvents dark chip production, the probability of storage loss due to shrinkage and disease increases. Wild Solanum species form the backbone of many potato-breeding programs. In this study, we evaluated 36 different plant introductions (PI) including 20 different species, grown in Madison and Rhinelander, Wis., to identify germplasm resistant to CIS for genetic analysis. After storage for 2–3 months at 4 °C, tuber sugar and amino acid content were analyzed via HPLC and slices were fried to determine chip color. Sugar and chipping data support previous research indicating CIS resistance in S. okadae, S. raphanifolium, and S. phujera. Interestingly, some germplasm selections with high reducing sugar content produced light-colored chips, indicating exceptions to the typical correlation between reducing sugar content and chip color. Genetic bases to these exceptions are under evaluation.
Jorge Siller-Cepeda, Manuel Baez-Sañudo, Rosalba Contreras-Martinez, Laura Contreras-Angulo, Rosabel Velez, and Dolores Muy-Rangel
Banana fruits `Cavendish' type were obtained from a warehouse at color green stage. At arrival, fruits were taken out of boxes, dipped into a thiabendazole solution for 5 minutes, dried at room temperature and separated into three lots. One lot was sprayed with Fresh Seal™ (FS) at 3 °Brix, a second lot was treated with Semper Fresh™ (SF) at 1.2%, and the third was left as a control. After that, all fruits were packed again inside the plastic bags within the original carton boxes. Film-coated and control fruits were ethylene treated for 24 hours at 150 ppm, and vented for 24 hours until they reached color 3 (more green than yellow). After that, film-coated and control fruit boxes were collected inside 238-L airtight containers to apply Smartfresh™ (SMF) treatments at 0 and 300 ppb for 12 hours at 22 °C, complementing six different treatments. Later, fruits were stored at 22 °C and 80% to 90% relative humidity for 5 days to follow up changes. Quality evaluations were registered every day, including weight loss, firmness, color, CO2, ethylene, pH, titratable acidity, °Brix, and sugar spots. SF alone and the combinations SF + SMF and FS + SMF reduced weight loss as compared with the other treatments. SMF alone or in combination with FS or SF maintained higher firmness and delayed yellow color development as compared with the other treatments. Combinations of SF or FS with SMF delayed and reduced the incidence of sugar spots as compared with control fruits. Chemical characteristics were not significantly affected by the treatments, but SF + SMF had higher acidity and a lower pH. All treatments reached between 20 and 21 °Brix after 5 days. The data show that combined treatments of SMF and film coatings reduce sugar spot incidence, improving appearance and extending yellow life of fruits.
John R. Stommel and Kathleen G. Haynes
Fruit of the cultivated tomato (Lycopersicon esculentum Mill.) store predominantly glucose and fructose whereas fruit of the wild species L. hirsutum Humb. & Bonpl. characteristically accumulate sucrose. Reducing sugar and sucrose concentrations were measured in mature fruit of parental, F1, F2, and backcross (BC1) populations derived from an initial cross of L. esculentum `Floradade' × L. hirsutum PI 390514. Generational means analysis demonstrated that additive effects were equal to dominance effects for percentage of reducing sugar. It was determined that a single major gene, dominant for a high percentage of reducing sugar, regulates the percentage of reducing sugar in tomatoes. We propose that this gene be designated sucr. Only additive effects were demonstrated to be important for glucose: fructose ratios. Using L. hirsutum as a donor parent for increasing total soluble solids concentration in the cultivated tomato is discussed.
Steven Raines, Cynthia Henson, and Michael J. Havey
role in the ability of onion to increase DW and soluble solids concentrations. McCallum et al. (2006) observed strong negative correlations between reducing sugars and fructans and identified a major quantitative trait locus (QTL) on chromosome 8 for
Barbara J. Daniels-Lake, Robert K. Prange, Stephanie D. Bishop, and Kimberly Hiltz
light fry color depends on low reducing sugar concentrations in the raw tubers ( Burton et al., 1992 ; Mazza, 1983 ). Although researchers and industry experts have long believed that elevated CO 2 in the storage atmosphere results in increased
Rosilene Barbosa de Franca, Gerson Renan de Luces Fortes, and Adriano Nunes Nesi
The aim of this work was to evaluate the effect of sucrose on the in vitro muliplication of potato, cultivars Baronesa, Macaca, and Cristal. The nutrient medium used was the MS basal salts and vitamins added to 100 mg·L-1 myo-inositol. Four sucrose concentrations (20, 30, 40, and 50 g·L-1) were tested. The pH was adjusted to 5.9 before autoclaving. Each treatment had 15 explants, which were collected from the lower part of the shoot containing two buds. This material was inoculated in a 250-mL flask with 40 mL of nutrient medium. After inoculation the flasks were kept in a growth room under 25 ± 2 °C, 16-h photoperiod, and 19 μMol·m-2·s-1 radiation provided by cool-white fluorescent lamps for 30 days. This trial was designed in a randomized block with three replicates. Every 7 days, the parameters were collected as follows: number of buds, shoot length and number of shoots. It was observed that `Baronesa' presented the highest number of buds and rate of multiplication. `Cristal' had a slightly better performance for these parameters. Plants treated with sucrose at 50 g·L-1 led to a higher number of shoots. However, `Macaca' treated with sucrose at 40 g·L-1 had the highest shoot length.
Barbara Daniels-Lake, Robert Prange, and John Walsh
For many years, the accepted wisdom among potato storage researchers and industry personnel linked the accumulation of CO2 in the storage atmosphere to darkening of potato fry color. Dark fry color is undesirable in the potato processing industry, as consumers prefer light-colored finished products. Previous research to elucidate the effect of CO2 has presented conflicting results. In three consecutive years of storage trials, the effects of elevated CO2 concentrations, reduced O2 concentrations and ethylene gas on the fry color and sugar content of `Russet Burbank' potato (Solanum tuberosum L.) tubers were evaluated. The potatoes were stored in modified atmosphere chambers and selected atmosphere mixtures were supplied from compressed gas cylinders. Four 3-week trials were conducted in 2002 and two 9-week trials were conducted in each of 2003 and 2004. Fry color and tuber sugars were assessed at the start of each trial and after several weeks of exposure to the treatment atmospheres. Compared with untreated controls, increased CO2 alone or in combination with decreased O2 had little or no effect on fry color or tuber sugars. During the second and third years, only selected treatments were repeated, with or without the addition of 0.5 μL·L–1 ethylene gas. Ethylene is known to affect potato fry color and reducing sugars. In three of four trials, tubers exposed to ethylene alone had darker fry color and higher reducing sugars compared with controls. Applied treatments had little or no effect on fry color and sugars in the fourth trial. Interestingly, in the same three of four trials, fry color of tubers exposed to both elevated CO2 and ethylene gas was not only darker than controls but also darker than tubers treated with ethylene alone. Similarly, reducing sugar concentrations were higher in tubers exposed to both ethylene and CO2 than with ethylene alone. No similar interaction between ethylene and oxygen concentration was observed. The results suggest a synergistic negative effect of trace ethylene and elevated CO2 on fry color, which may explain the apparently contradictory findings of some published research examining the effects of CO2 on potato fry color.
Thanaa M. Ezz, Mark A. Ritenour, and Jeffrey K. Brecht
Heat treatments and exposure to elevated CO2 are known to reduce the incidence of chilling injury on grapefruit. In the current study, `Marsh' grapefruit (Citrus paradisi Macf.) were harvested on 17 Jan. or 22 Mar. 1996 and exposed to hot water (HW) dips (48 °C for 120 minutes) or exposed to controlled atmosphere (CA) of 10% or 16% CO2 during the first 3 weeks of an 8-week cold storage period (4.5 °C) to test their effects on the development of peel pitting (i.e., chilling injury) and proline and other compositional changes of the peel and juice. All HW and CA treatments from both harvests greatly reduced the development of peel pitting compared to the control. These treatments were also associated with lower average proline levels in the flavedo during storage. This suggests that HW and elevated CO2 may reduce chilling-induced peel pitting by facilitating proline metabolism in grapefruit flavedo tissue. HW and CA treatments resulted in higher peel total soluble and nonreducing sugar levels, but effects on peel reducing sugar and free amino acid concentrations were not consistent. In the juice, HW reduced titratable acidity (TA) concentrations while CA tended to increase both TA and ascorbic acid concentrations. Compared to the control, CA resulted in a slight decrease in total soluble solids during storage, while the effect of HW was inconsistent.
K.I. Theron and G. Jacobs
Flowering-size Nerine bowdenii bulbs were sampled from a commercial planting at 2-week intervals from 13 Aug. 1991 to 14 June 1992. They were dissected, the dry weight of foliage and leaf bases was recorded, and carbohydrate analysis was performed on the foliage leaves, leaf bases, and roots. Starch was the dominant storage carbohydrate, and leaf bases were the principal bulb structures where it was stored. Changes in starch content closely followed dry weight changes in the bulb. When exposed to low temperatures, starch was converted to sugars. Except for these high levels in the leaf bases, sugars, expressed both as concentration and total content, were low in bulb components, indicating continued export and conversion to starch. Low sugar levels during the period that florets in the current season's inflorescence develop to stage Late G (gynoecium elongated, carpels fused) is implicated in the abortion of the inflorescence.