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Ioannis P. Oikonomakos, Niels O. Maness, Donna Chrz, William McGlynn, and Penelope Perkins-Veazie

Lycopene from ground watermelon flesh can be segregated between filtrate and filter cake by coarse filtration. Low speed centrifugation of the filtrate can further segregate filtrate lycopene between an easily recoverable precipitated high lycopene pellet and a serum. Lycopene in watermelon flesh increases steadily during maturation and remains constant, or slightly decreases in overripe melons. This study was conducted to document the effect of melon maturity on lycopene segregation during filtration/centrifugal processing. Flesh of three seedless watermelon cultivars was ground and filtered through two layers of Miracloth. Filter cakes were rinsed with water and filtrates were centrifuged at 3500 g to precipitate lycopene. Centrifugal recovery of lycopene from filtrates was about the same for undermature and mature melons (50% to 70%), but was much lower for overripe melons (35% to 45%). This decline in recoverable lycopene from overripe melons could be negated if ground flesh was heated to 60 or 85 °C prior to filtration. Lycopene from preheated flesh segregated predominately into the filter cake for all three maturity groupings. The interaction between melon maturity and pre-filtration heating will be evaluated and integrated into a potential watermelon lycopene production system.

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Penelope Perkins-Veazie, Julie K. Collins, John R. Clark, and Lawrence Risse

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John R. Clark, James N. Moore, Jose Lopez-Medina, Chad Finn, and Penelope Perkins-Veazie

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Chen Jiang, Penelope Perkins-Veazie, Sylvia M. Blankenship, Michael D. Boyette, Zvezdana Pesic-VanEsbroeck, Katherine M. Jennings, and Jonathan R. Schultheis

A series of studies were conducted to better understand the occurrence and causes of internal necrosis (IN) in ‘Covington’ sweetpotato (Ipomoea batatas). Assessment of the problem among the industry was done for 2 years and revealed that IN was widespread in commercial storage facilities throughout the state of North Carolina; both incidence and severity were generally low (<10% incidence with minimal severity of symptoms). A few storage rooms had a high percentage of IN with severe storage root symptoms but results were inconsistent across years and among rooms. Preharvest studies with commercially used insecticides did not induce IN, but the harvest aid ethephon consistently induced IN with an incidence higher than 50%. Internal necrosis symptoms were not detectable at harvest, and earliest consistent incidence was observed 6 days after harvest (DAH) during the curing phase. Symptoms became more prevalent and severe at 30 DAH. However, in commercial storage rooms, no relationship was found between IN incidence and postcuring storage temperature or relative humidity (RH) conditions. Sweetpotato storage roots stored in air-tight barrels and exposed to 100 ppm ethylene after curing showed no relationship between the presence of ethylene gas in storage and incidence of IN. Our results indicate that IN incidence of ‘Covington’ is erratic with no obvious cause among storage rooms and that initiation of IN may occur most frequently during the first week following harvest.

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Edgar L. Vinson III, Floyd M. Woods, Joseph M. Kemble, Penelope Perkins-Veazie, Angela Davis, and J. Raymond Kessler

Mini-watermelon [Citrullus lanatus (Thunb.)] cultivars Valdoria and Vanessa were evaluated at 20, 30, 40, or 50 days after anthesis to determine maturity at harvest. Fruit circumference, weight, ground spot color, and number of senescent tendrils were measured as external indicators for each watermelon. Soluble solids content (SS), pH, and SS:total acid ratio (SS:TA) of each watermelon were determined to provide an indication of internal maturity. Regression and Akaike Information Criterion fit statistics analyses were performed to determine significant relationships and best predictors for external indicators of internal maturity factors. In this study, external predictors were most closely linked to fruit pH rather than to SS or SS/TA. Of the external indicators tested, fruit weight, circumference, number of senescent tendrils, and International Commission on Illumination (CIE) b* color coordinate values of the ground spot were best related to fruit pH. According to the regression models, two completely senesced tendrils, a circumference of 53 cm, weight of 3 kg, and CIE b* coordinate ground spot value of 40 are each sufficient to predict maturity when pH is used as the internal indicator of maturity under the conditions of this experiment.

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Penelope Perkins-Veazie, Julie Collins, Richard Hassell, Steve Olson, Donald Maynard, Jonathan Schultheis, Missy O'Hern, Toni Magby, and Shelli Magby

Mini watermelons are the size of cantaloupes and weigh 1.5 to 3 kg (4 to 8 lbs). Melons of 18 selections were grown in replicated trials in North Carolina, South Carolina, and north and south Florida. Melons were harvested when ripe, and samples of heart and locule tissue were frozen and sent to Lane, Okla. A total of 960 samples, representing 6-12 melons per selection per location, were analyzed for total lycopene content using colorimeter and spectrophotometer methods. Subsamples of `Mohican', `Hazera 6007', `Vanessa', `Petite Treat', and `Precious Petite' were analyzed by HPLC for carotenoid profiles. Total lycopene content ranged from 52 to 108 μg·g-1, depending on variety. Selections were grouped into two levels of lycopene content. The varieties Precious Petite, Petite Perfection, Betsy, Bonny, Petite Treat, Valdoria, Vanessa, Hazera 5133 and 5138, RWT 8149, 8155, 8162 had 60 to 79 μg·g-1 lycopene and the varieties Hazera 6007, 5123, 5109, 5177, Mohican, and Extazy had 80 to 100 μg·g-1. Melons harvested from the Florida locations had more total lycopene than those from North and South Carolina. `Precious Petite' had more β-carotene as a percentage of total carotenoids than other varieties tested. These results indicate that lycopene content is affected primarily by germplasm and also by environment.

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Angela R. Davis, Charles L. Webber III, Wayne W. Fish, Todd C. Wehner, Stephen King, and Penelope Perkins-Veazie

Producers of fresh fruits and vegetables face increasing production costs and international market competition. Growers who can offer high-quality watermelons [Citrullus lanatus (Thumb.) Matsum. & Nakai] that are also highly nutritious will have better market opportunities. To accomplish that, germplasm must be identified that has enhanced phytonutrient levels. Surprisingly, there is little information on the genetics of nutritional quality in watermelon. The present study was performed on 56 watermelon cultivars, breeding lines, and PI accessions (hereafter collectively referred to as cultigens) to determine the importance of genotype and environmental effects on L-citrulline concentration in fruit, an amino acid that helps regulate blood pressure. Our results demonstrated that L-citrulline concentration was affected by environment and the amount of environmental effect varies among cultigens. The mean of fruit tested in Lane, OK, was 3.10 mg·g−1 fresh weight and in College Station, TX, it was 1.67 mg·g−1 fresh weight. All cultigens had a higher mean L-citrulline concentration when grown in Lane, OK, instead of College Station, TX. Additionally, the L-citrulline concentration varied considerably within cultigens; i.e., ‘Congo’ had a 1.26 to 7.21 mg·g−1 fresh sample deviation. The cultigen ‘AU-Jubilant’ had the most stable L-citrulline concentration (2.23 to 4.03 mg·g−1 fresh deviation) when tested from one location. Environment did not significantly increase within-genotype variation (average se of 10 cultigens tested at each location was ± 35.3% for College Station, TX, and ± 32.9% for Lane, OK). L-citrulline concentration did not correlate with watermelon type (open-pollinated or F1 hybrid) or flesh color (red, orange, salmon yellow, or white). Differences among cultigens for L-citrulline were large (1.09 to 4.52 mg·g−1 fresh sample). The cultigens with the highest L-citrulline concentration were ‘Tom Watson’, PI 306364, and ‘Jubilee’. These could be used to develop cultivars having a high concentration of L-citrulline.

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Charles L. Webber III, Angela R. Davis, James W. Shrefler, Penelope Perkins-Veazie, Vincent M. Russo, and Jonathan V. Edelson

The increasing perception by consumers that organic food tastes better and is healthier continues to expand the demand for organically produced crops. The objective of these experiments was to investigate the impact of different weed control systems on yields of watermelon (Citrullus lanatus var. lanatus) varieties grown organically. Six watermelon varieties were transplanted at two locations (Lane and Center Point, Okla.). The six varieties included three seeded varieties (`Early Moonbeam', `Sugar Baby', and `Allsweet') and three seedless varieties (`Triple Crown', `Triple Prize', and `Triple Star'). The weed control system at Lane utilized black plastic mulch on the crop row, while the area between rows was cultivated to control weeds. The no-till organic system at Center Point used a mowed rye and vetch cover crop, hand weeding, and vinegar (5% acetic acid) for weed control. When averaged across watermelon varieties, Lane produced significantly more fruit per plant (4.2 vs. 2.3 fruit/plant), greater marketable yields (16.0 vs. 8.4 kg/plants), and higher average marketable weight per fruit (6.1 vs. 4.0 kg) than at Center Point. When comparing locations, four of six varieties had significantly greater number of fruit per plant and higher marketable yields at Lane than at Center Point. Except for `Early Moonbeam', all other varieties produced significantly heavier fruit at Lane than at Center Point. In contrast, the Center Point location produced a greater percentage of marketable fruit for all varieties except `Allsweet'. Fruit quality (lycopene and °Brix) was as good or greater when harvested from the weedier Center Point location.

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Matthew B. Bertucci, Katherine M. Jennings, David W. Monks, Jonathan R. Schultheis, Penelope Perkins-Veazie, Frank J. Louws, and David L. Jordan

Grafting watermelon (Citrullus lanatus) is a common practice in many parts of the world and has recently received increased interest in the United States. The present study was designed to evaluate early season growth, yield, and fruit quality of watermelon in response to grafting and in the absence of known disease pressure in a fumigated system. Field experiments were conducted using standard and mini watermelons (cv. Exclamation and Extazy, respectively) grafted onto 20 commercially available cucurbit rootstocks representing four species: giant pumpkin (Cucurbita maxima), summer squash (Cucurbita pepo), bottle gourd (Lagenaria siceraria), and interspecific hybrid squash [ISH (C. maxima × Cucurbita moschata)]. Nongrafted ‘Exclamation’ and ‘Extazy’ were included as controls. To determine early season growth, leaf area was measured at 1, 2, and 3 weeks after transplant (WAT). At 1 WAT, nongrafted ‘Exclamation’ produced the smallest leaf area; however, at 3 WAT, nongrafted ‘Exclamation’ produced the largest leaf area in 2015, and no differences were observed in 2016. Leaf area was very similar among rootstocks in the ‘Extazy’ study, with minimal differences observed. Marketable yield included fruit weighing ≥9 and ≥3 lb for ‘Exclamation’ and ‘Extazy’, respectively. In the ‘Exclamation’ study, highest marketable yields were observed in nongrafted ‘Exclamation’, and ‘Exclamation’ grafted to ‘Pelops’, ‘TZ148’, and ‘Coloso’, and lowest marketable yields were observed when using ‘Marvel’ and ‘Kazako’ rootstocks, which produced 47% and 32% of nongrafted ‘Exclamation’ yield, respectively. In the ‘Extazy’ study, the highest marketable yield was observed in nongrafted ‘Extazy’, and ‘Kazako’ produced the lowest yields (48% of nongrafted ‘Extazy’). Fruit quality was determined by measuring fruit acidity (pH), soluble solids concentration (SSC), lycopene content, and flesh firmness from a sample of two fruit from each plot from the initial two harvests of each year. Across both studies, rootstock had no effect on SSC or lycopene content. As reported in previous studies, flesh firmness was increased as a result of grafting, and nongrafted ‘Exclamation’ and ‘Extazy’ had the lowest flesh firmness among standard and mini watermelons, respectively. The present study evaluated two scions with a selection of 20 cucurbit rootstocks and observed no benefits in early season growth, yield, or phytonutrient content. Only three of 20 rootstocks in each study produced marketable yields similar to the nongrafted treatments, and no grafted treatment produced higher yields than nongrafted ‘Exclamation’ or ‘Extazy’. Because grafted seedlings have an associated increase in cost and do not produce increased yields, grafting in these optimized farming systems and using fumigated soils does not offer an advantage in the absence of soilborne pathogens or other stressors that interfere with watermelon production.

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Allan F. Brown, Gad G. Yousef, Ivette Guzman, Kranthi K. Chebrolu, Dennis J. Werner, Mike Parker, Ksenija Gasic, and Penelope Perkins-Veazie

The objective of this study was to examine the relative impact of genetics and environment on phenolic and carotenoid profiles in peach (Prunus persica) germplasm. Fully mature, (“ready-to-eat” stage) firm fruit of peach cultivars China Pearl, Contender, and Carolina Gold were collected from established trees at two North Carolina locations in 2009 and 2010. Advanced breeding selections NC Yellow and NC 97-48 were collected from a single location in both years. Using tandem extractions and chromatography analyses, 10 carotenoids and 24 phenolic compounds were quantified separately in the peel and flesh. Statistically significant differences were noted among peach cultivars and advanced selections for β-carotene, cyanidin-3-glucoside, cyanidin-3-rutinoside, cholorogenic acid, quercetin-3-glucoside, and individual procyanidins. Peel anthocyanin (ANC) concentration ranged from 183 mg/100 g in ‘Contender’ to non-detectable levels in NC97-48 and NC Yellow. ‘China Pearl’ and ‘Carolina Gold’ produced ANC levels approximately half of ‘Contender’. Chlorogenic acid concentration also fit a discrete pattern of accumulation but was not related to the accumulation of ANC. ‘China Pearl’, NC 97-48, and NC Yellow contained the highest levels of chlorogenic acid (105 to 136 mg/100 g), ‘Carolina Gold’ contained the lowest (52 mg/100 g), and ‘Contender’ represented an intermediate phenotype (70 mg/100 g). Statistically significant genetic variation was found for almost all compounds identified, whereas location and year effects tended to be compound-specific. For chlorogenic acid, 28% of the phenotypic variance was explained by location (year = nonsignificant), whereas 40% of the phenotypic variation of ANC was explained by differences in years (location = nonsignificant). Analyzing fruit from the same environment over 2 years or from two locations in the same year would not have adequately accounted for the variation associated with environment. The detailed phytochemical profile of peach reported here demonstrates the importance of multiyear, multilocation analysis in revealing accurate measures of phytochemical genetic variation and provides a comprehensive baseline analysis of phytochemicals in commonly grown peach cultivars that can be used to evaluate novel germplasm.