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Different responses of two melon (Cucumis melo L.) genotypes (Şemame, drought and salt-tolerant and Ananas, drought and salt-sensitive) to drought stress with or without humic acid (HA) treatment were studied. The experiment was carried out under greenhouse conditions. The experimental design was two factorial randomized block with 4 replicates. HA treatment increased the shoot fresh and dry weights and leaf area of both genotypes under drought stress. HA stimulated accumulation of K and Ca ions, chlorophyll (SPAD value) and antioxidant enzyme activity (superoxide dismutase-SOD, catalase-CAT and glutathione reductase-GR) in both genotypes. This effect was more clear in the Şemame genotype than in Ananas. As a result, HA treatment has been proved to influence the ability of melon genotypes to cope with drought stress and to increase their tolerance. [ABSTRACT FROM AUTHOR]

Cucurbit downy mildew, caused by the oomycete Pseudoperonospora cubensis (Berck & Curtis) Rostovtsev, is one of the most important diseases of melons in Costa Rica. The control of downy mildew by the application of conventional fungicides in combination with resistance inducers was investigated on melon (Cucumis melo L.) cv. 'Ruidera'. Two systemic fungicides, mefenoxam (1.96 kg a.i.ha-1) and dimethomorph (0.45 kg a.i.ha-1), and a sequence of the protectant fungicides chlorothalonil/mancozeb (2.01/1.20 kg a.i.ha-1), were applied, by themselves or in combination with application of each of 3 resistance inducers, phosphite (1.01 kg a.i.ha-1), menadione sodium bisulphite (MSB, 0.14 kg a.i.ha-1) and acibenzolar-S-methyl (ASM, 0.02 kg a.i.ha-1). Controls with no fungicides or no inducers were included in the experiment. Significant differences (p<0.05) in area under the disease progress curve (AUDPC) were observed among fungicides. The lowest values of AUDPC were obtained with the chlorothalonil/ mancozeb sequence, and with dimethomorph. Mefenoxam was not effective. The combination with phosphite improved the efficacy of all the conventional fungicides. No effect in disease control was observed with the application of MSB or ASM, either alone or combined with conventional fungicides. The treatments chlorothalonil/mancozeb and dimethomorph were less expensive than other treatments with lower efficacy. [ABSTRACT FROM AUTHOR]

Cantaloupe (Cucumis melo L. var. reticulatus Naudin) were evaluated during development and then fresh-cut cubes were stored after preparation from various maturities to track quality changes during storage. Flowers were anthesis tagged one morning in two seasons (years) and developing fruit were harvested weekly at 13, 20, 27 to 28, and 34 to 35 days after anthesis (DAA). Mature fruit were harvested at 37 to 38 DAA with five distinct maturities: ¼-, ½-, ¾-slip, full-slip (FS), and overripe (OR). Hunter L* and a* color values indicated a change from pale green to light orange that occurred 28 DAA. There were significant decreases in L*, a*, and b* by day 9 in storage (4 °C) as fresh-cut cubes. After 28 DAA, sucrose dramatically increased, and this was positively correlated with increases in both total sugars (r = 0.882, P = 0.084) and percent soluble solids concentration (r = 0.939, P = 0.041). Gradual deterioration occurred during storage, as determined by a uniform subjective quality criterion, which was independent of maturity. There was a negative linear trend in hand-held and instrumental firmness over the length of storage for each maturity level, and the slopes decreased significantly with increasing maturity, indicating the effect of storage duration decreased as harvest maturity increased. There was a significant increasing trend in vitamin C (P = 0.042) during development from 12 through 35 DAA, then losses were greater in fresh-cut cubes prepared from full-slip fruit (65%) than less-mature fruit: ¾-slip, 50%; ½-slip, 48%; ¼-slip, 40%. The pH of mesocarp tissue dropped to the lowest value (5.25) just before physiological maturity at 27 to 28 DAA, then peaked after harvest (6.51-6.79), and declined somewhat by the end of storage as fresh-cut cubes. In sum, muskmelon fruit used to produce fresh-cut cubes should be harvested ⩾½-slip to attain optimum physiological quality and consumer acceptability. [ABSTRACT FROM AUTHOR]

The relationship between sugar accumulation and sucrose metabolism enzyme activities was studied among seven genotypes of Cucumis melo L., covering the broad genetic range of sucrose accumulation found in the species. The primary determinant correlated with sucrose levels was the genetic variation for developmental loss of soluble acid invertase (AI) activity. Sucrose accumulation in the developing fruit began only when AI activity declined to less than an experimentally determined threshold value, and continued until removal of the fruit from the plant. In addition, the activities of sucrose phosphate synthase (SPS), sucrose synthase (SuSy), and neutral invertase (NI) were all positively correlated with sucrose accumulation among the genotypes. The low-sucrose-accumulating genotypes were characterized by low activities of each of the three enzymes, irrespective of their invertase activities. Final sucrose content was best predicted for each genotype by the number of days the fruit remained attached to the plant while characterized by ‘sucrose accumulation metabolism,’ which was characterized primarily by AI activity less than threshold values, together with SPS, SuSy, and NI activities higher than threshold levels. [ABSTRACT FROM AUTHOR]

A likely reason why consumers are not repeat buyers of many fresh-cut fruit is inconsistent or unsatisfactory flavor and/or textural quality. Research toward understanding mechanisms responsible for generation, and/or loss of flavor compounds in fresh-cut fruit is limited. Solid phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) were utilized to study flavor volatile profiles in anthesis-tagged cantaloupe (Cucumis melo L. var. reticulatus Naud. cv. Sol Real) during growth, development, and for fresh-cuts prepared from fruit with five distinctly different harvest maturities. One-quarter-slip fruit had a clearly green, well-attached peduncle; 1/2-slip fruit had a distinct abscission detectable at the peduncle, 3/4-slip fruit were approaching commercial harvest, full-slip (FS) fruit are or will cleanly separate from the vine with light pressure; and over-ripeness (OR) was precisely categorized as 2 days past FS. Recovery of total volatiles displayed a linear response and most volatile clasps (except aldehydes) generally followed a trend upon processing where FS > 3/4-slip > 1/2-slip > 1/4-slip. On day 0, only 70.0%, 37.7%, and 20.5% total volatiles were recovered in 3/4-slip, 1/2-slip, and 1/4-slip fruit, compared to FS fruit. During fresh-cut storage, percent total esters followed an increasing linear trend that was maturity-dependent. Percent total aromatics and percent aldehydes followed a linear trend that was maturity-dependent whereby 1/4-slip > 1/2-slip > 3/4-slip > FS. During storage, the relative percentage of acetates decreased, and displayed a maturity-dependent curvilinear trend. The magnitude of the slope decreased with maturity, indicating that the effect of storage time decreased as maturity increased. In FS, 3/4-slip, 1/2-slip, and 1/4-slip cubes, acetates comprised 66.9% of all compounds recovered on day 0 yet, only 26.1% to 44.2%, and 21.3% to 32.6% remained on days 9 and 14, respectively. For all maturities, a curvilinear increase in relative percentage of nonacetate esters was observed during storage. There was a uniform change in the ester balance (nonacetate ester:acetate ratio) during fresh-cut storage, which was independent of initial processing maturity. The overall ester ratio changed roughly 2-fold after just 2 days in optimum storage, and after 5 days it increased more than 3-fold. The shift in endogenous ester compounds could be partially responsible for the apparent loss of characteristic flavor in fresh-cut cantaloupe through long-term storage. [ABSTRACT FROM AUTHOR]

Cantaloupes (Cucumis melo) in three separate trials were cut into 1-inch cubes and irradiated at 0, 0.25, 0.5, 0.75, 1.0, 1.25, or 1.5 kGy; 0, 0.1, 0.2, 0.3, 0.4, 0.5, or 0.7 kGy; and 0, 0.3, 0.6, or 0.9 kGy, respectively. They were then stored in air at 3 °C for up to 20 days, and respiration rate, measured as carbon dioxide (CO2) production, microbiological counts [total plate count (TPC) and yeast and molds], texture, and color were measured during storage. Respiration rates were initially higher in irradiated cantaloupe. After 8 days, respiration was similar between irradiated and control fruit. Irradiation moderated increases in respiration in a dose-dependent manner. Highest irradiation doses resulted in initial TPC reductions of 1.5 log compared to the non-irradiated controls, and also prevented the 2.5 to 3 log TPC increases seen in controls after 10 to 11 days of storage. Texture differed on day 1, when controls were most firm, but irradiation maintained greater firmness than controls after day 7. Irradiation of fresh-cut cantaloupe has potential for shelf life extension and for integration with modified atmosphere packaging systems. [ABSTRACT FROM AUTHOR]

An abstract of the article "Cellular antioxidant activity of common fruits," by K. L. Wolfe and colleagues is presented.