Fruit of the cultivated strawberry (Fragaria ×ananassa Duchesne ex Rozier) are a good source of natural antioxidants, which play an important role in protecting human health. Antioxidant levels vary considerably among strawberry genotypes. The cultivated strawberry is a hybrid of two very different wild progenitor species: F. virginiana Mill. and F. chiloensis (L.) Mill. The progenitor species are valued by strawberry breeders as sources of novel traits, but have not been evaluated for antioxidant capacity or levels of antioxidant compounds. The objectives of this study are 1) to evaluate the antioxidant contents and antioxidant activities in representatives of F. virginiana and F. chiloensis in comparison with representatives of the cultivated strawberry species (F. ×ananassa), 2) to determine which strawberry compounds are most closely correlated with antioxidant capacity among these three species, and 3) to identify wild strawberry genotypes with high antioxidant activity and bioactive compounds for use in cultivar development. Fruit of 19 accessions from each of the three species, cultivated strawberry plus the two progenitor species (F. ×ananassa, F. virginiana, and F. chiloensis), were evaluated for levels of antioxidant capacity (oxygen radical absorbance capacity), total phenolics, total anthocyanins, ellagic acid, quercetin 3-glucoside plus quercetin 3-glucuronide, kaempferol 3-glucoside, kaempferol 3-rutinoside, p-coumaryl–glucose, pelargonidin 3-glucoside, pelargonidin 3-glucoside–succinate, cyanidin 3-glucoside, and cyanidin 3-glucoside–succinate. Fruit of the 13 accessions tested from the wild progenitor species F. virginiana had significantly higher antioxidant capacity, total phenolics, and total anthocyanins than did the fruit of three accessions tested from the cultivated strawberry F. ×ananassa, or the three accessions tested from the other wild progenitor species (F. chiloensis), and will be valuable as a source of parent material for developing more nutritious strawberry cultivars. The high correlation with antioxidant capacity, relative efficiency, and lack of genotype-by-year interaction in this study suggests that the measurement of total phenolics may be the better assay to use for the later selection stages in a strawberry cultivar development program. Of the evaluated F. virginiana accessions, NC 95-19-1, JP 95-1-1, CFRA 0982, NC 96-5-3, and RH 30 fruit were highest in antioxidant capacity and should prove useful toward development of strawberry cultivars with high antioxidant capacities.
Shiow Y. Wang and Kim S. Lewers
Shiow Y. Wang, Kim S. Lewers, Linda Bowman, and Min Ding
Fruit extracts from 17 to 18 representatives of three strawberry species [Fragaria virginiana Mill., F. chiloensis (L.) Mill., and F. ×ananassa Duchesne ex Rozier] were tested for the ability to inhibit proliferation of A549 human lung epithelial cancer cells. The fruit extracts also were tested for activities against free radicals, (peroxyl radicals, hydroxyl radicals, singlet oxygen, and superoxide radicals), the activities of antioxidant enzymes [glutathione peroxidase (EC 126.96.36.199), superoxide dismutase (EC 188.8.131.52), guaiacol peroxidase (EC 184.108.40.206), ascorbate peroxidase (EC 220.127.116.11), monodehydroascorbate reductase (EC 18.104.22.168), dehydroascorbate reductase (EC 22.214.171.124), and glutathione reductase (EC 126.96.36.199)], and the activities of nonenzyme antioxidant components, ascorbic acid and glutathione. Correlations between the proliferation of cancer cells and these antioxidant activities were calculated. At the species level, F. virginiana fruit extract inhibited the proliferation of A549 human lung epithelial cancer cells to a significantly greater extent (34% inhibition) than the extracts from fruit of either F. chiloensis (26%) or F. ×ananassa (25%) (P < 0.0001). Extracts from fruit of F. virginiana also had significantly greater antioxidant activities and higher activities of antioxidant enzymes and nonenzyme components than did extracts from the other two species. Among individual genotypes, there was a high positive correlation between antiproliferation of A549 cancer cells, antioxidant activities against free radicals, activities of antioxidant enzymes, and activities of nonenzyme components. Although all fruit extracts from all the strawberry genotypes inhibited proliferation of A594 cancer cells, fruit extracts from seven F. virginiana genotypes showed significantly greater antiproliferative effects than any of the F. ×ananassa or F. chiloensis genotypes. These genotypes, CFRA 0982, JP 95-1-1, NC 95-19–1, RH 30, NC 96-48-1, JP 95-9-6, and LH 50-4, may be especially useful in developing cultivars with greater anticancer potential.
S. Y. Wang, H. J. Jiao, and M. Faust
An increase in ascorbic acid, reduced form of glutathione (GSH), total glutathione, total non-protein thiol (NPSH) and non-glutathione thiol (RSH) occurred as a result of induction by thidiazuron during bud break, whereas dehydroascorbic acid and oxidized glutathione (GSSG) decreased during the same period. Thidiazuron also enhanced the ratio of GSH/GSSG, and activities of catalase, superoxide dismutase (SOD), ascorbate free radical reductase (AFR), ascorbate peroxidase (POD), dehydroascorbate reductase (DHAR), ascorbate oxidase (AAO), and glutathione reductase (GR). The ascorbic acid content and the activities of catalase, SOD, AFR, POD, AAO, and DHAR peaked when buds were in the side green or green tip stage just prior to the start of rapid expansion, and declined thereafter. The GSH, NPSH, RSH, ratio of GSH/GSSG, and activity of GR increased steadily during bud development.
F.D. Moore III, S.R. Nath, and Y-C Wang
Duration of growth is dependent on morphological events or changes in growth rate. It is the latter that is associated with phasic development. The most productive phase of plant growth is the linear or constant rate phase, primarily because it endures longer than the exponential phase. The purpose of our research was to objectively determine the true tree-height growth pattern, the linear and stationary phases of height growth, and to mathematically derive the maximum slope (maximum growth rate) of the growth curve, its location (inflection point), and the maximum slope of the logarithmic form (maximum relative growth rate) of the growth curve. The data were composed of 333 tree-height records covering 240 years from 200 beechwoods in the U.K. Height-age data were fitted using a splined function (S) and the Chapman-Richards function (CR). The growth curve and critical points on the curve were derived from the CR model. The linear phase began when trees were 9 and lasted 43 years. However, the stationary phase did not begin until age 162. Anecdotal evidence suggests that very little fruiting occurs before age 50. Based on derived critical points and anticipated source-sink dynamics, the reproductive stage should have taken place during the progressive “deceleration phase” when trees were between 31 (location of the maximum slope, also inflection point) and 162 (from quadratic root). The linear phase ended at 52 years, (coinciding with minimum acceleration) and may prove a more accurate estimate than 31. Maximum slope was 1.2 m per year occurring at age 31. Maximum slope of the log curve was 0.14 m·m–1 per year. The advantage of the CR function and the importance of the derived quantities and growth phases will be discussed.
H. Wang, S. Parent, A. Gosselin, and Y. Desjardins
Micropropagated plantlets of Gerbera jamesonii H. Bolus ex Hook. F. `Terra Mix', Nephrolepis exaltata (L.) Schott `Florida Ruffles', and Syngonium podophyllum Schott `White Butterfly' were inoculated with two vesicular-arbuscular mycorrhizal (VAM) fungi, Glomus intraradices Schenck and Smith and G. vesiculiferum Gerderman and Trappe. They were potted in three peat-based media to determine the effects of mycorrhizal peat substrate on acclimatization and subsequent growth of micropropagated plantlets under greenhouse conditions. Symbiosis was established between the three ornamental species and VAM fungi within 4 to 8 weeks of culture in the greenhouse, but not during acclimatization. Mortality of Gerbera and Nephrolepis mycorrhizal plantlets was reduced at week 8 compared to the noninoculated control. A peat-based substrate low in P and with good aeration improved VAM fungi spread and efficiency. Mycorrhizal substrates had a long-term benefit of increasing leaf and root dry weight of Gerbera and Nephrolepis. Mycorrhizal Gerbera plants flowered significantly faster than non-mycorrhizal plants.
Julia M. Harshman, Wayne M. Jurick II, Kim S. Lewers, Shiow Y. Wang, and Christopher S. Walsh
Raspberries are a delicate, high-value crop with an extremely short shelf life exacerbated by postharvest decay caused by Botrytis cinerea Pers. European red raspberry (Rubus idaeus L.) is the most widely grown variety. Yellow (R. idaeus L.), black (R. occidentalis L.), and purple raspberries (R. ×neglectus Peck. or R. occidentalis ×idaeus hybrids) are available mainly at local markets and U-pick farms. To compare the postharvest quality of the raspberry color groups, pesticide-free fruit from cultivars and breeding selections of red, yellow, purple, and black raspberries were examined for oxygen radical absorbance capacity (ORAC), phenolics, anthocyanins, soluble solids, titratable acids, pH, color, firmness, decay and juice leakage rates, ethylene evolution, and respiration. There were significant correlations between decay rate and physiochemical properties. Both decay and leakage rates were correlated with weather conditions before harvest, but each color group responded differently to different weather factors. There were no correlations among changes in color, firmness, decay, or juice leakage rates. All the other color groups were less acidic than the familiar red raspberry. Yellow raspberries had the worst decay rates but the best leakage rates. Black and purple raspberries, with the highest phenolics and anthocyanins and the lowest ethylene evolution rates, resisted decay the longest but bled soonest.
S. Y. Wang, J. L. Maas, E. M. Daniel, and G. J. Galletta
Ellagic acid (EA) a naturally occurring polyphenol in many fruit and nut crops, is a putative inhibitor of certain chemically-induced cancers. Improved methods of extraction, detection and quantification are essential for accurate determination of EA for plant physiological and genetic studies and animal nutrition and chemopreventative studies. Column (C18) preconditioning significantly reduced column retention of EA. An ammonium phosphate/methanol solvent system was used in preference to sodium phosphate/methanol. Fruit sample determinations were 10-100 times higher than previously reported, due to the improvements in efficiency of these methods. EA levels (mg/g dry wt) were: strawberry pulp (1.55), achene (8.46), root (1.55), crown (3.32) and leaf (14.27); blackberry pulp (,2.43) and seed (3.37); and cranberry skin (1.06), pulp (0.31), seed (0.69), leaf (4.10).