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  • Author or Editor: Paul Chen x
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`D'Anjou' pears (Pyrus communis, L.) growing in 3 locations with the elevation at 150 meters, 380 meters, and 610 meters respectively in Hood River valley, Oregon were harvested at the commercial maturity with the flesh firmness of 62.3 Newton (±2.2 N) and stored in air at -1°C. Regardless of different growing elevations, the incidence of superficial scald became noticeable after 2.5 months of storage and became substantial after 3 months. The rate of scald development was higher on the fruit from 150 meters elevation than those from higher elevations. Alpha-farnesene and conjugated trienes in the peel tissue accumulated at faster and higher rates in the fruit from 380 meters and 610 meters elevations than those from 150 meter elevation. The threshold level of conjugated trienes which causes superficial scald disorder was different from the fruit grown at different elevations.

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`D'Anjou' pears (Pyrus communis L.) harvested at commercial maturity and stored in air at 30 °F (-1 °C) for up to 7 weeks were still incapable of ripening normally at 68 °F (20 °C) for 7 days. `D'Anjou' fruit at this stage were termed as under-chilled fruit. Ziploc bags [1-gal (3.8-L)] perforated with a number of small holes [1/8 inches (0.32 cm) in diameter] were used to pack five `d'Anjou' pears and five `Bartlett' pears [a total net weight of 5 ± 0.2 lb (2.3 ± 0.1 kg)]. The mixed fruit packed in the same bags were placed into a room at 68 °F. When under-chilled `d'Anjou' fruit packed with `Bartlett' fruit in the bags perforated with 6, 8, or 10 holes, `Bartlett' fruit became fully ripe after 5 days while `d'Anjou' fruit were capable of ripening normally after 7 days at 68 °F. Ripened fruit of both pear cultivars developed high dessert quality. The concentration of ethylene in these bags accumulated to ≈50 ppm (mg·L-1) on day 4 while CO2 concentration did not increase to above 3% and O2 concentration maintained at 18%. Ethylene generated naturally by `Bartlett' pears during ripening at 68 °F and accumulated in the bag perforated with 6 to 10 holes was sufficient to induce the normal ripening activities of under-chilled `d'Anjou' pears. This packaging technology may be used to promote early marketing for both pear cultivars.

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Abstract

The viability of apple blossom buds after test freezing was quantitatively estimated by the technique of electrical conductivity combined with visual observation. A sharp increase in the percent of leaching always indicated freezing injury to the blossom. This technique can provide not only a quantitative estimation of freezing injury but it can detect small differences in the cold tolerance existing between species.

Open Access

St. augustinegrass (Stenotaphrum sp.) is a warm-season perennial turfgrass that grows widely in tropical regions around the world. St. augustinegrass is valued for both its turf performance and high levels of resistance to biotic and abiotic stresses. The current study was aimed at developing nuclear microsatellite markers for st. augustinegrass. Pyrosequencing of an enriched microsatellite library on the Roche FLX platform using a 454 Titanium kit produced 57,306 sequence reads; 2614 of which contained short tandem repeats. One hundred primer pairs were tested with 18 accessions from the U.S. Department of Agriculture National Plant Germplasm System st. augustinegrass collection grown in Griffin, GA. This collection contains both Stenotaphrum dimidiatum and Stenotaphrum secundatum accessions. Among revealed 100 primer pairs, 33 were polymorphic. A total of 175 alleles were amplified. The number of observed alleles per primer pair ranged from two to 10, with an average of 5.3. Shannon’s information index and Nei’s genetic diversity values were 0.4403 and 0.2873, respectively. This set of microsatellite markers is useful for assessment of genetic diversity and construction of molecular genetic linkage maps in st. augustinegrass.

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`Bartlett' pears were treated with 300 nL·L-1 1-MCP at 20°C for 24 h shortly after harvest, and were stored at -1 °C in either regular atmosphere (RA) or controlled atmosphere (CA: 1.5 kPa O2 / 0.5 kPa CO2). After 2 and 4 months of RA storage, or 4 months of CA storage, fruit were pre-conditioned at 10 °C, 15 °C or 20 °C for 5, 10, or 20 days, respectively. Pre-conditioned fruit were then held at 20 °C for 14 days to simulate marketing conditions. Flesh firmness (FF) and extractable juice (EJ) were monitored during the marketing period. The optimal stage of ripeness for `Bartlett' pears was defined to be when FF decreases to 27 N and EJ decreases to 55 mL/100 g. The proper pre-conditioning combinations of temperature and duration were 15 °C or 20 °C for 10 d or 10 °C for 20 d if the fruit had been stored in RA for 2 months, 10 °C or 15 °C for 5 d if the fruit had been in RA for 4 months, and 20 °C for 10 d or 10°C for 20 d if the fruit had been in CA for 4 months, for which combinations the fruit ripened within a week and maintained quality for 14 days at 20 °C. The treatment combinations of lower temperature and/or shorter duration times in pre-conditioning delayed the ripening response of the fruit, and combinations of higher temperature and/or longer duration times in pre-conditioning resulted in a shorter marketing life because of senescence breakdown, in comparison the optimal combinations mentioned above. These results indicate that pre-conditioning regimes for 1-MCP treated `Bartlett' pears are storage atmosphere and time dependent. Generally, CA stored fruit needed more preconditioning (in terms of higher temperature and/or longer duration) than did RA stored fruit.

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An assay for pyruvate kinase (PK) was tested as a diagnostic tool for cork spot, a major physiological disorder in pear Pyrus communis L. cv. d'Anjou) fruit. PK activity and Ca and protein concentrations were measured in peel of normal and affected fruit during selected months in 2 years. Protein concentration was more closely associated with cork spot than PK activity or Ca concentration. These preliminary results suggested the PK assay was a poor diagnostic tool for cork spot.

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Abstract

Water stress and short day treatments increased the frost hardiness and the water saturation deficit (WSD) of stems of red-osier dogwood (Cornus stolonifera L.) plants grown for 21 days at controlled temperatures, photoperiods, and water supply. Potted plants were watered either to the point of saturation (control) or with lesser amounts (98, 60, or 30 ml/pot per day). Hardiness and WSD were proportional to the level of water stress. The greatest increase in hardiness (from −3 to −11°C) occurred in die 38 ml treatment during the first 7 days. Prolonging water stress, for an additional 14 days, induced little additional hardiness. There was no increase in the hardiness (−3°C) or WSD of control plants grown under long days (14 hours). Control plants grown at short days (10 hours) increased in hardiness from −3 to −6.5°C and WSD increased from 7.5% to 18.2% in 21 days. Water stress or short days caused significant increases in hardiness and WSD, but a combination of the 2 treatments caused no further increase in hardiness or WSD.

Open Access

Exposure of young pepper plants to chilling temperatures delays the development of terminal flower buds to flowering during post-stress growth. Degree of adverse influence depends on chilling intensity, exposure duration and varietal sensitivity. `Ma Belle' pepper plants were grown in a greenhouse (GH) during winter months on the St. Paul campus, No supplemental lighting was provided. When plants were at the 2- to 3-leaf stage, they were foliar sprayed with mefluidide (Technical grade) at 0, 5, 10 and 15 ppm. One day after treatment, some plants were transferred from GH to a cold room (3° ∼4°C day/night) with 12-h photoperiod. Treatad plants remaining in the GH served as the control. Plants were chilled for 1, 2, 4 and 6 days and then brought back to the GH for post-stress growth and development observation. Treated and untreated plants grown in the GH showed no difference in days to flowering, and reached 50% flowering at about 62 days after treatment. When untreated plants were chilled for 1,2,4 and 6 days, they showed a delay of 8, 18, 30 and 34 days, respectively, to flowering, If not killed, as compared to the control The long delay to flowering was due to the injury of the terminal flower buds. After 4 and 6 days of chilling, most terminal flower buds were killed. However, when plants were treated with mefluidide and subsequently chilled days to flowering were significantly shortened. A difference of 10-12 days was observed between chilled untreated plants and chilled treated plants. Concentrations of 5 to 15 ppm were equally effective in protection against chilling.

Free access

Exposure of young pepper plants to chilling temperatures delays the development of terminal flower buds to flowering during post-stress growth. Degree of adverse influence depends on chilling intensity, exposure duration and varietal sensitivity. `Ma Belle' pepper plants were grown in a greenhouse (GH) during winter months on the St. Paul campus, No supplemental lighting was provided. When plants were at the 2- to 3-leaf stage, they were foliar sprayed with mefluidide (Technical grade) at 0, 5, 10 and 15 ppm. One day after treatment, some plants were transferred from GH to a cold room (3° ∼4°C day/night) with 12-h photoperiod. Treatad plants remaining in the GH served as the control. Plants were chilled for 1, 2, 4 and 6 days and then brought back to the GH for post-stress growth and development observation. Treated and untreated plants grown in the GH showed no difference in days to flowering, and reached 50% flowering at about 62 days after treatment. When untreated plants were chilled for 1,2,4 and 6 days, they showed a delay of 8, 18, 30 and 34 days, respectively, to flowering, If not killed, as compared to the control The long delay to flowering was due to the injury of the terminal flower buds. After 4 and 6 days of chilling, most terminal flower buds were killed. However, when plants were treated with mefluidide and subsequently chilled days to flowering were significantly shortened. A difference of 10-12 days was observed between chilled untreated plants and chilled treated plants. Concentrations of 5 to 15 ppm were equally effective in protection against chilling.

Free access

The brown color development on the skin of three varieties of pears (Bartllet, Packham's T. and Anjou) was characterized between 200 and 300 nm from hexane extracts of pear peel discs, with and without the application of the antioxidant Ethoxyquin (2700ppm) during -1°C storage and 20°C ripening. All the varieties presented a main peak at 232nm (afarnesene), which decreased in the storage as scald increased.

Absorbance at 259, 269, and 280nm (conjugated trienes) were characteristic of Anjou and Packham's Triumph fruits susceptible to the disorder. Bartlett fruits had a major peak at 259nm without the other secondary peaks.

The application of ethoxyquin reduced the oxidation of a farnesene, the formation of the conjugated trienes and intensity of scald in Packham's Triumph and Anjou fruits. However in Bartlett fruits this antioxidant was not very effective to reduce the scald.

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