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Senay Ozgen, Mustafa Ozgen, and Jiwan P. Palta

Several recent studies, including from our laboratory, have provided evidence that by improving tuber calcium level, we can improve tuber quality such as low internal defects and better storability. The purpose of this study was to be determine the influence of supplemental calcium fertilization on tuber size and tuber number. For this purpose, plantlets of Solanum tuberosum cv. Russet Burbank raised in tissue culture were planted in 20-L pots filled with sandy loam soil with pH of 6.9 and soil calcium level of 350 ppm. All treatments received same total amount of nitrogen (at the rate of 280 kg·ha–1). Five treatments were evaluated: i) nonsplit nitrogen (from ammonium nitrate), ii) split nitrogen (from ammonium nitrate), iii) split nitrogen + gypsum, iv) split nitrogen (from liquid nitrogen) + calcium chloride, and v) split nitrogen (from calcium nitrate). The total calcium was applied at the rate of 168 kg·ha–1. Gypsum application was made at 4 weeks after planting, and other sources of calcium were applied on a split schedule (equally split at 4, 6, 8 weeks after planting). Four months after planting, tubers were harvested and evaluated. In general, all calcium treatments had lower tuber number and greater tuber size compared to the nonsplit nitrogen control. The percentage of total A-grade tubers as well as the percentage yield from A-grade tubers was increased by all calcium applications. These results suggest that calcium content I the soil can influence both potato tuber number and tuber size.

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Mustafa Ozgen, Senay Ozgen, and Jiwan P. Palta

Recent studies from our laboratory have demonstrated that lysophoshatidylethanolamine (LPE) is able to accelerate fruit ripening while at the same time promoting shelf life. LPE is a natural lipid and is commercially extracted from egg yolks and soybeans. We studied the influence of LPE on the pattern of anthocyanin accumulation and storage quality of cranberry fruit (Vaccinium macrocarpon Ait. cultivar Stevens). For this purpose 2 x 2-m plots were established in cranberry beds at two separate locations near Wisconsin Rapids. Experiments were conducted in 1997 and 1998 seasons. Plots were sprayed with LPE (extracted from egg yolk and soybean) 3 to 4 weeks before harvest. Spray solution included 200 ppm LPE, 3% ethanol, and 0.1% detergents (either Tergitol or Sylguard). Fruit samples were taken from a part in the plot periodically to determine the changes in the fruit. The rest of the plots were commercially wet harvested with a machine and stored in cold storage. Marketable fruit were counted at various times of cold storage to determine effect of LPE on shelf life of cranberries. In general, application of LPE from both sources resulted in 20% to 35 % increase in fruit anthocyanin contents. Also LPE treatment resulted in 10% to 20% increase in marketable fruit in cold storage. A postharvest dip of cranberry fruit with 50 ppm LPE solution for 15 min also resulted in about a 20% to 30% increase in marketable berries during cold storage. The results of this study shows that pre- and postharvest applications of LPE can add value to cranberry crop including better and more uniform colored fruit, enhance self life, and earlier harvest.

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Mustafa Ozgen and Jiwan P. Palta

Ethephon [2-(chloroethyl) phoshonic acid] is used widely to maximize the yield of ripe tomato fruit. However, ethephon causes rapid and extensive defoliation, overripening, and promotes sunscald damage to the fruit. Recent studies from our laboratory have provided evidence that lysophoshatidylethanolamine (LPE) can reduce leaf senescence. We investigated the potential use of LPE to reduce damaging effect of ethephon on tomato foliage. Three-month-old tomato plants (variety Mountain Spring) grown in greenhouse conditions were sprayed with 200 ppm LPE (with 3% ethanol) at 6 and 24 h before ethephon treatment. After 8 days, plants treated with ethephon alone showed about 80% foliar damage while plant treated with LPE before ethephon treatment showed about 25% foliar damage. In a parallel study, LPE together with ethephon was found to maintain three to four times greater chlorophyll content in the leaves compared to ethephon alone. Treatments of LPE did not reduce the fruit ripening response by ethephon. Both sources of LPE were effective in preventing damaging effects of ethephon on the foliage. These results suggest that LPE treatments 6 and 24 h before ethephon application can prevent damaging effects of ethephon on foliage while allowing the acceleration of fruit ripening.

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Mustafa Özgen, Karim M. Farag, Senay Ozgen, and Jiwan P. Palta

Highly colored cranberries are desired for both fresh and juice markets. Berries accumulate more color when allowed to stay on the vines longer. However, early fall frosts often force growers to harvest before the fruit has reached its optimal color. This is especially true for the berries under the canopy. No product is currently available for grower to accelerate the color development in cranberries. Result from recent studies suggests that a natural lipid, lysophosphatidylethanolamine (LPE), can accelerate color production in fruit and, at the same time, promote shelf life. LPE is a natural lipid and is commercially derived from egg and soy lecithin. The influence of LPE on anthocyanin accumulation and storage quality of cranberry fruit (Vaccinium macrocarpon Ait. `Stevens') was studied. Cranberry plants were sprayed with LPE at about 4 weeks before commercial harvest at multiple locations. Experiments were conducted in 1997, 1998 and 1999. Fruit samples were taken at 2 and 4 weeks after spray application to determine the changes in the fruit color. Plots were wet harvested using a standard commercial method and stored in a commercial cold storage facility. Marketable fruit were evaluated at 1 and 2 months after cold storage to determine effect of LPE on shelf life of cranberries. In general, a preharvest application of LPE resulted in a 9% to 27% increase in fruit anthocyanin concentration compared to the control. LPE treatments also resulted in 8% to 12% increase in marketable fruit compared to the control following cold storage. Influence of LPE on fruit quality was more apparent after 1 month of storage. These results are consistent with the observed effects of LPE on tomatoes. Interestingly ethanol application also enhanced storage quality. Our results suggest that a preharvest application of LPE may have the potential to enhance color and prolong shelf life of cranberry fruit.

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Mustafa Özgen, Sookhee Park, and Jiwan P. Palta

Mitigation of ethylene promoted leaf senescence by lysophosphatidylethanolamine (LPE) was studied. Micropropagated `Russet Burbank' potato (Solanum tuberosum L.,) plantlets were grown on MS media in sterile culture tubes. After 2 weeks of growth, tubes were sealed and ethylene gas was applied to obtain 5 nL·L–1 final concentration in the culture tubes. Observations and measurements were taken two weeks after ethylene injection. Potato plantlets treated with ethylene showed severe leaf senescence symptoms such as epinasty, lack of growth, yellowing and axillary shoot formation. These observations indicate that apical dominance has been lost with ethylene treatment. The same experiment was repeated with different concentrations of LPE in the MS medium. Inclusion of 50 or 100 mg·L–1 of LPE in the medium mitigated the damage normally caused by applied ethylene. Leaves of plantlets exposed simultaneously to LPE and ethylene had significantly higher chlorophyll content and more healthy leaves compared to plantlets grown on medium lacking LPE. Results of this study suggest that LPE may have the potential to retard ethylene-promoted leaf senescence and may mitigate ethylene induced loss in apical dominance of micropropagated potato plantlets.

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Mustafa Ozgen, Jiwan P. Palta, and Stephen B. Ryu

Ethephon [2-(chloroethyl) phoshonic acid] is used widely to maximize the yield of ripe tomato fruits. However, ethephon causes rapid and extensive defoliation, overripening, and promotes sunscald damage to the fruit. Recent studies from our laboratory have provided evidence that lysophosphatidylethanolamine (LPE) can reduce leaf senescence. We investigated the potential use of LPE to reduce damaging effect of ethephon on tomato foliage and influence on the activity of phospholipase D (PLD). Disruption of membrane integrity has been suggested as a primary cause of senescence in plants. PLD is known to be a key enzyme, which initiates the selective degradation of membrane phospholipids in senescing tissues. Two-month-old tomato plants (`Mountain Spring') grown in greenhouse condition were sprayed with water, 200 ppm LPE, and 1000 ppm ethephon. In addition, LPE spray prior to ethephon or mixture with ethephon were also tested. Leaves were sampled after 0, 2, 5, 24, 72, and 168 h of spray application, for PLD activity measurements. Spray of LPE prior to ethephon spray or inclusion of LPE in the ethephon spray reduced foliar injury by ethephon. Activity of soluble PLD was increased dramatically in leaves sprayed with ethephon initially and than dropped by 7 days. We also found that LPE-treated leaves had lower PLD activity than the ethephon-treated leaves. Plants treated with LPE-ethephon mixture also showed significantly lower PLD activity. These results suggest that LPE treatments mitigate ethephon injury to tomato plants. Furthermore, it appears that this mitigation involves modulation of the activity of PLD.

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Mustafa Ozgen, Artemio Z. Tulio Jr., A. Raymond Miller, R. Neil Reese, and Joseph C. Scheerens

In preliminary studies, we found that relative and absolute antioxidant (AO) levels varied within and among small fruit types. AO levels were affected by assay method used, time of reaction, volume of sample, and the ratio of reactants to total AO activity. To identify the physicochemical parameters that affect accuracy and reproducibility, a series of experiments were conducted to test the roles of AO assay, different AOs, and AO concentration on measured AO content and reaction kinetics. Three assays (DPPH, FRAP, ABTS) were used to evaluate AO capacity of seven fruit types (black and red raspberry, blackberry, strawberry, grape, elderberry, and cranberry) and nine purified AOs (ascorbic, caffeic, chlorogenic, gallic, and ellagic acids, α-tocopherol, trolox, cyanidin-3-glucoside, and quercetin). Ascorbic acid, trolox, caffeic acid, chlorogenic acid, and α-tocopherol exhibited simple reaction kinetics and reached endpoints quickly, regardless of assay. Gallic and ellagic acids, quercetin, cyanidin-3-glucoside, and all fruit extracts exhibited more complex kinetics and long reaction times (>70 min) to reach an endpoint. Moreover, the latter four AOs had the highest AO capacity among the compounds tested. We observed differences in reactivity between assays, compounds and fruit extracts, but relative AO activity was comparable, although the absolute values differed. Since AO capacity of fruit extracts is a composite of the individual AOs present, it is important that reactions progress to near steady state, assay reactants are in excess of (30–50×) the AO capacity being measured, more than one assay is used to describe the total AO activity of fruit samples. Thus, there may not be a single AO assay method that completely defines the AO activity of a given fruit.

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Mustafa Ozgen, Joseph Kovach, Lauren D. Harper, Simeon Wright, and Joseph C. Scheerens

Six strawberry cultivars (`Earliglow', `Honeoye', `Idea', `Jewel', `Northeaster', and `Seneca') were grown organically on three different composts (yard waste, dairy barn waste, and vermicompost). Organic treatments were contrasted against a synthetic fertilizer standard, a conventional pesticide standard and an untreated control. Plots were rated for tarnished plant bug (Lygus lineolaris) damage during the growing season. At harvest, berries were examined for their ascorbic acid levels and total anthocyanin and phenolic contents. Ascorbic acid content of berries in different cultivars and treatments were similar. As expected, fruit anthocyanin and phenolic contents were significantly different among the cultivars, and ranged between 160–230 μg·gfw-1 and 1039–1333 μg·gfw-1, respectively. Among treatments, anthocyanin contents of strawberries were not significantly different, but berries grown on the conventional pesticide standard had 8% to 12% lower total phenolic content than the other treatments. In organic treatments, production of phenolic compounds may have been induced in response to increased tarnished plant bug feeding. This putative biotic stress defense mechanism was seen most dramatically on tarnished plant bugsusceptible cultivars. However, as differences in phenolic levels were greater among cultivars than among treatments, cultivar choice may be a more important consideration than growing system for optimizing antioxidant levels in commercially available fruit.

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Salih Kafkas, Mustafa Özgen, Yıldız Doğan, Burcu Özcan, Sezai Ercişli, and Sedat Serçe

Mulberries (Morus L.) show a great deal of genetic variability and adaptability to various environments. There are more than 24 species of mulberries in cultivated and wild forms. In Turkey, three Morus species, M. alba L., M. nigra L., and M. rubra L., are grown. In this study, we attempted to characterize 43 Morus accessions originating from distinct regions of Turkey using fluorescent dye amplified fragment length polymorphism (AFLP) markers and capillary electrophoresis. The accessions belonged to M. alba, M. nigra, and M. rubra; M. alba consisted of white- and purple-fruited samples. Eight primer combinations generated a total of 416 bands, 337 of which were polymorphic (80.5%). Resolving powers of the AFLP primers ranged from 0.410 to 0.942 making a total of 5.015, whereas the polymorphic information content ranged from 0.662 to 0.898 with an average of 0.812. Unweighted pair-group method of arithmetic mean (UPGMA) clustering of the accessions showed three major groups representing M. nigra, M. rubra, and M. alba accessions. The M. alba group had two subgroups that were not correlated with fruit color. The UPGMA dendrogram of average taxonomic differences confirmed these results. The principle coordinate analysis demonstrated that M. nigra accessions had limited genetic variation. In conclusion, our study indicated that M. nigra and M. rubra are molecularly distinct from M. alba. Our results also suggest that M. nigra accessions having a low level of morphological variation are molecularly similar.

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Mustafa Ozgen, Artemio Z. Tulio Jr., Ann M. Chanon, Nithya Janakiraman, R. Neil Reese, A. Raymond Miller, and Joseph C. Scheerens

To investigate the variation in the phytonutrients of Cornelian cherry (Cornus mas L.), fruit was harvested at the blush (S1), red (S2), and ripe (S3) stages from five genotypes maintained at the Secrest Arboretum, Wooster, Ohio. The S1-S3 samples were characterized for color reflectance and then frozen at –28 °C. After storage, samples were analyzed for dry weight (DW), total soluble solids (TSS), sugars (FRU + GLU), organic acids (ORG), total phenols (PHE), total anthocyanins (ACY), individual anthocyanins (IA), hydroyzable tannins (HT), and antioxidant capacity (FRAP and ABTS). From S1 to S3, DW and TSS increased by 24% and 21%, respectively, and L, hue angle, and chroma values decreased. On a DW basis, all analytical parameters were significantly influenced by genotype and stage. The ACY levels rose 7-fold during ripening, but PHE contents declined by 10%. In ripe fruit, HT comprised the bulk of the PHE constituents, whereas ACY accounted for only 7.6% of PHE levels. Variability among genotypes was moderate for all ripe fruit parameters but ACY. Ripe fruit varied little in color parameters and ACY (fwb) and IA (fwb) were not significantly different among cultivars. The Cy 3-gal and pel 3-gal levels were negatively correlated. Antioxidant capacity declined 16% to 18% during ripening. Ripe fruit FRAP and ABTS values were higher than those reported for most fruits, averaging 596 ± 85 and 629 ± 85 μmol TE eq./gDW, respectively. ABTS and FRAP values were highly correlated with each other and with PHE and HT contents, but were loosely and negatively related to ACY levels. Considering our limited sample size, we concluded that the phytonutrient capacity of cornelian cherry is substantial, predominantly associated with tannins and moderately variable among genotypes.