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J.K. Peterson and H.F. Harrison Jr.

Sweetpotato resin glycosides were purified by HPLC methods. Most allelopathic potential could be explained by these compounds. Fifty percent inhibition (I50) of seed germination was obtained for redroot pigweed at 160 ppm, for velvetleaf at 13 ppm and for prosomillet at 11 ppm. Seed of the congeneric species I. purpurea was not sensitive. Growth of yellow nutsedge was drastically reduced, the I50 for shoot growth was 30 ppm, for number of roots 36 ppm, and for total root length 19 ppm. The glycosides accounted for approximately half of the total fungicidal activity of all extract fractions when tested on Fusarium oxysporum pv. batatae. At 2 mg per ml, the glycosides inhibited hyphal growth by 31%. This concentration is less than 10% of the glycoside concentration in dry periderm tissue of `Regal'. The purified glycosides were incorporated into a meridic diet for diamondback moth larvae. All observed antibiosis was caused by the glycosides; the LD50 was 7.2 mg per ml diet. At that concentration the surviving larvae showed a weight decrease of 46%.

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John R. Stommel* and Robert J. Griesbach

Anthocyanins contribute to color development in economically important vegetables, fruits and floral crops. Their expression is critical to product sensory quality attributes, potential nutritive value, and stress response. Anthocyanins are synthesized in response to numerous environmental factors including temperature and light stress and pathogen attack. We have developed several Capsicum lines, including `02C27', expressing anthocyanin pigmentation differentially in various tissues (leaf, stem, fruit and flower). HPLC analysis demonstrated that the anthocyanins within the fruit, flower and leaves of Capsicum `02C27' were identical and that the major anthocyanidin was a delphinidin glycoside. Line `02C27' exhibits anthocyanin foliar pigmentation that is accumulated differentially in response to temperature stress. Under unfavorable low temperature (20 °C day/18 °C night), mature Capsicum leaves contained 4.6 times less anthocyanin per gram fresh weight than under high (30 °C day/28 °C; day/night) temperatures. Besides containing less anthocyanin in mature leaves, young immature leaves did not develop color as quickly under the lower temperature. Utilizing cloned and sequenced gene fragments of pepper chalcone synthase (CHS), dihydroflavonol 4-reductase (DFR), and anthocyanidin synthase (ANS), we evaluated the role of transcription in regulation of flavonol biosynthesis. Analysis of anthocyanin composition and gene expression data indicated that the block in anthocyanin formation in less pigmented leaves occurred at anthocyanin synthase. In contrast to wild tupe plants, this mutant also exhibited reduced flowering and failed to set fruit under high temperature, long day conditions.

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Thomas C. Koch* and Irwin L. Goldman

Carotenoids (provitamin A) and tocopherols (vitamin E) are powerful antioxidants in plants and in the human diet. Carrot (Daucus carota) has been selected for increased levels of carotenoids, contributing to its orange color and reported health benefits. Selection for increased tocopherol has shown success in seed oils, but little progress has been made in the edible portions of most vegetable crops. HPLC measurement following a simultaneous heptane extraction of both compounds has shown a significant (P ≤ 0.001) positive correlation of α-tocopherol with α-carotene (r = 0.65) and β-carotene (r = 0.52). To increase both the tocopherols and carotenoids in plants, 3 populations have been established from select open-pollinated varieties grown in 2002. These populations consist of half-sib families with these differing selection schemes: based strictly on increased α-tocopherol levels; an index to increase α-carotene, β-carotene and α-tocopherol; and a random population in which no selection is occurring. After one cycle of selection, populations were grown on muck soil during the summer of 2003. Compared with the random population, an increase of 24.68% in α-tocopherol concentration was recorded for the population selected strictly on α-tocopherol while increases of 8.47% in α-tocopherol, 9.31% in α-carotene and 7.31% in β-carotene were recorded for the population with index selection. The continuation of these carrot populations shows promise to produce carrot germplasm with improved human nutritive value.

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Bhimanagouda S. Patil and Ashok K. Alva

Accumulating epidemiological evidences indicate that citrus phytochemicals have prevented chronic diseases such cancer and heart diseases. To enhance nutraceutical levels, field experiments were conducted using `Ruby Red' grapefruit on Carrizo citrange rootstock to evaluate the effects of variable fertilizer rates on nutraceutical contents. The trees received annual nitrogen rates from 0 to 280 kg·ha-1 (using a 1 N: 0.25 P: 1 K blend) under optimal irrigation schedule. Subsamples of fruit were analyzed for nutraceutical levels. HPLC analysis showed that naringin concentrations of the fruit collected from the trees treated with different levels of nitrogen differ significantly, and naringin levels decreased with increased nitrogen levels. Fruit from the control treatment had 1316 mg·mL-1 of naringin compared to the fruit collected from 280 kg N/ha per year trees (1056 mg·mL -1). A similar trend was observed with tasteless flavonoid naringenin rutinoside (narirutin). Total vitamin C [ascorbic acid (AA) plus dehydroascorbic acid (DHAA)] content from the fruit collected decreased with the nitrogen levels increased. These results demonstrate that increased fertilizer rates have an influence on the nutraceutical levels; therefore, there is a potential for further investigations on fine tuning the preharvest production programs to improve the nutritional value of the fruit.

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Mark G. Lefsrud and Dean A. Kopsell

Chlorophyll and carotenoid pigments were measured with high-performance liquid chromatography (HPLC) during leaf development in kale (Brassicaoleracea L. var. acephala D.C). Lutein and β-carotene are two plant-derived carotenoids that possess important human health properties. Diets high in these carotenoids are associated with a reduced risk of cancer, cataracts, and age-related macular degeneration. Kale plants were growth-chamber grown in nutrient solution culture at 20 °C under 500 μmol·m-2·s-1 of irradiance. Pigments were measured in young (<1 week), immature (1-2 weeks), mature (2-3 weeks), fully developed (3-4 weeks) and senescing (>4 weeks) leaves. Significant differences were measured for all four pigments during leaf development. Accumulation of the pigments followed a quadratic trend, with maximum accumulation occurring between the first and third week of leaf age. The highest concentrations of lutein were recorded in 1- to 2-week-old leaves at 15.1 mg per 100 g fresh weight. The remaining pigments reached maximum levels at 2-3 weeks, with β-carotene at 11.6 mg per 100 g, chlorophyll a at 251.4 mg per 100 g, and chlorophyll b at 56.9 mg per 100 g fresh weight. Identifying changes in carotenoid and chlorophyll accumulation over developmental stages in leaf tissues is applicable to “baby” leafy greens and traditional production practices for fresh markets.

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John L. Maas, Shiow Y. Wang, and Gene J. Galletta

Ellagic acid in tissue extracts of green and red-ripe strawberries (Fragaria × ananassa Duch.) was detected and quantified by HPLC. Ellagic acid content of green fruit pulp ranged from 1.32 to 8.43 mg·g-1 of tissue dry weight (mean 3.36 mg·g-l) and in achenes of green fruit from 1.32 to 20.73 mg·g-1 (mean 7.24). Ellagic acid content of red fruit pulp at one location for 35 cultivars and selections ranged from 0.43 to 4.64 mg·g-1 of dry weight (mean 1.55) and from 0.43 to 3.47 mg·g-l (mean 1.45) for 15 clones at another location. Achenes from red-ripe fruit ranged from 1.37 to 21.65 mg·g-1 (mean 8.46) for 34 clones at one location and from 2.81 to 18.37 mg·g-1 (mean 8.93) for 15 clones at another location. Leaf ellagic acid content ranged from 8.08 to 32.30 mg·g-1 of dry weight (mean 14.71) for 13 clones examined. Large differences in ellagic acid content were found among cultivars, but tissue values were not consistent within cultivars. Values from one tissue type did not correlate consistently with values of the other tissues. Sufficient variation was found among cultivars to suggest that increased ellagic acid levels may be achieved in progeny from crosses with selected parental material.

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J.B. Magee and C.L. Gupton

The organic acid composition of blueberries of three highbush (Vaccinium corymbosum) cultivars, three rabbiteye (V. ashei cultivars and nine southern highbush (V. corymbosun hybrids) cultivars or selections was determined by HPLC. Species means off the individual acids (citric, malic, succinic, and quinic), expressed as a percentage of total acid, formed profiles or patterns that are thought to be characteristic of the species. Citric (75%) was the predominant acid in highbush fruit with lesser percentages of succinic (13%), quinic (9.6%), and malic (2.7%). The percent composition of rabbiteye berries [quinic (49%), succinic (39%), citric (6.7%), malic (5%)] was distinctly different from highbush. The acid profile of southern highbush fruit reflected their V. corymbosum heritage with an acid profile similar to that of highbush. When related to a clone's pedigree, these results suggest that organic acid profiles may be a useful screening tool for studying the contribution of southeastern native species such as V. darrowi or V. ashei to the inheritance of organic acids.

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Alison R. Cutlan, John E. Erwin, and James E. Simon

Parthenolide, a biologically active sesquiterpene lactone found in feverfew [Tanacetum parthenium (L.) Schultz. Bip.], has been indirectly linked to the antimigraine action of feverfew preparations. Commercial products of feverfew leaves vary widely in parthenolide content (0-1.0%/g dwt). No comprehensive studies have quantified parthenolide variation among feverfew populations or cultivars, and whether morphological traits are correlated with this natural product. In this study, 30 feverfew accessions were examined for parthenolide content, morphological traits, and seed origin. Statistically significant differences in parthenolide levels were found among the populations studied. Parthenolide content ranged from (0.012% ± 0.017 to 2.0% ± 0.97 /g dwt) as determined by HPLC-UV-MS. Higher parthenolide levels tended to be in wild material (0.41% ± 0.27) as opposed to cultivated material (0.19% ± 0.09). Parthenolide levels correlated with flower morphology: disc flower (0.49% = B1 0.36), semi-double (0.38% ± 0.13), double (0.29% ± 0.16), and pompon-like flower (0.22 ± 0.14). Leaf color also appeared to be indicative of parthenolide levels, with the light-green/golden leafed accessions showing significantly higher parthenolide content than darker-leafed varieties, but whether this was due to inadvertent original selection of a high parthenolide-containing golden leaf selection is not yet known. This study does show that further selection for improved horticultural attributes and natural product content is promising to improve feverfew lines for the botanical/ medicinal plant industry.

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Chen-Yi Hung, Cindy B.S. Tong, and John R. Murray

The color of red potatoes is due to an accumulation of anthocyanins in periderm tissues. The objective of this study was to examine the effect of several factors on tuber redness. Using the red tuber-producing S. tuberosum ssp. tuberosum cultivar Norland, we observed that chroma (intensity of redness) and anthocyanin content of greenhouse-grown tubers decreased as tuber weight increased. There was a slight or no increase in hue (tint). We used HPLC to determine that pelargonidin and peonidin are the major anthocyanidins (aglycones of anthocyanins) in tuber periderm. The ratio of pelargonidin to peonidin increased as tuber weight increased up to 25 g fresh weight. The decrease in chroma was not due to an increase in cell sap pH; we observed a decrease in cellular pH as tuber weight increased. Controlled-atmosphere storage had no effect on tuber chroma or anthocyanin content compared to air storage. Methyl jasmonate, sucrose, or light treatment did not increase anthocyanin accumulation. Tubers exposed to light had less anthocyanin than those kept in the dark. We are examining the developmental expression of anthocyanin biosynthetic genes, as well as the effect of maize transcription factors on anthocyanin synthesis, in tuber periderm.

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Juan Manuel González Gonzalez, Oscar Rebolledo Dominguez, and Lourdes Diaz Jimenes

The responsible substances involved in the phenomenon of compability/incompatibility in Sapotaceae species during two phenological stages were elucidated. An experiment was carried out to determine the compatibility/incompatibility relationship between homografts and heterografts of Sapotaceae species during two phenological stages, and to identify the responsible substances involved in the phenomenon. In order to determine the compatibility/incompatibility between Sapotaceae species, heterograftings were made using the mamey [Calocarpumsapota(Jacq.) Merr.] as scion, and chicozapote [(Achrassapota(L.)] was used as rootstock. Grafting was conducted during the phenological stage of defoliation of the scion donor plant, as well as during budding. Homografts were also made using C. sapota on C. sapota in both phenological stages. Plant tissue samples were obtained from scions and rootstocks in both phenological stages, and they were used for HPLC analysis. Heterografts (C. sapota on A. sapota) showed 100% incompatibility in both stages, and lack of success during grafting was obtained; similar results were registered with the homografts (C. sapota on C. sapota) during the budding stage; however, during the defoliation stage, 80% successful grafting was obtained. The responsible substances involved in the phenomenon of compatibility/incompatibility using samples taken during the grafting day and 60 days after (C. sapota grafted on A. sapota during defoliation stage), were identified as catechin and epicatechin. Catechins are the responsible substances of incompatibility in the heterografts of C. sapota /A. sapotain both phenological stages, as well as during the budding stage in the homografts on C. sapota.