Strawberries contain high levels of antioxidants, which have been correlated with a decreased risk of chronic disease. To more fully characterize the antioxidant profiles and possible associated health benefits of this fruit, the total free and bound phenolic, total flavonoid, and total anthocyanin contents of eight strawberry cultivars (Earliglow, Annapolis, Evangeline, Allstar, Sable, Sparkle, Jewel, and Mesabi) were measured. Cultivar effects on phenolic contents were compared with antioxidant capacities, as measured by the total oxyradical scavenging capacity (TOSC) assay, and to antiproliferative activities, as measured by inhibition of HepG(2) human liver cancer cell proliferation in vitro. Free phenolic contents differed by 65% between the highest (Earliglow) and the lowest (Allstar) ranked cultivars. The water soluble bound and ethyl acetate soluble bound phenolic contents averaged 5% of the total phenolic content of the cultivars. The total flavonoid content of Annapolis was 2-fold higher than that of Allstar, which had the lowest content. The anthocyanin content of the highest ranked cultivar, Evangeline, was more than double that of the lowest ranked cultivar, Allstar. Overall, free phenolic content was weakly correlated with total antioxidant activity, and flavonoid and anthocyanin content did not correlate with total antioxidant activity. The proliferation of HepG(2) human liver cancer cells was significantly inhibited in a dose-dependent manner after exposure to all strawberry cultivar extracts, with Earliglow exhibiting the highest antiproliferative activity and Annapolis exhibiting the lowest. No relationship was found between antiproliferative activity and antioxidant content.

The production of Rubus is associated with many expectations from different interest groups. Consumers expect flavorful products with health-enhancing benefits at reasonable costs. They want fresh products at any time, and they expect the quality to be high. Growers want productive plants that yield high quality fruit with minimal labor inputs. Both groups want the production of Rubus to have a minimal impact on the environment. Over the last century, production systems have evolved incrementally, with progressive modifications to what was done before. However, what may be required to meet ever-increasing demands and expectations is a complete redesign of plants and production systems. Seven areas of research are suggested for Rubus workers, each of which could significantly impact production systems and help retain the strong, positive image that these fruits enjoy. New advances will require the cooperation of breeders, physiologists, agronomists, engineers and ecologists working together at the interface of their overlapping fields.

Microshoots of apple (Malus domestica Borkh.) rootstocks G. 65, G.30 and G.11 were transferred from stage II axillary shoot cultures to stage III rooting media containing 10 levels of indole-butyric acid (IBA) for four weeks to determine optimal conditions for rooting. Microshoots were inverted or left in an upright position. Rootstocks and microshoot position affected rooting and survival; the highest rooting was 30% for G.65 inverted with 2 mg.L-1 IBA, 100% for G.30 upright with 3 mg.L-1 IBA, and 100% for G.11 inverted with 1 or 2 mg.L-1 IBA. No single set of conditions provided consistent rooting in vitro, and plants were not always of high quality. In a second experiment, microshoots were rooted and acclimatized ex vitro in a custom-built fog chamber to assess the effect of two carbon dioxide levels (450 or 1350 mu mol.mol(-1)) and three light levels (30, 50 or 100 mu mol.m(-2).s(-1)). All rootstocks rooted equally well ex vitro, but survival varied. Plantlets had the highest dry mass, leaf area and growth rates under high light conditions compared to medium light or low light conditions. Supple mental carbon dioxide had no consistent effect. If plants survived fog chamber conditions, subsequent survival in the fog tunnel and greenhouse was 100%. Thus, these rootstocks can be rooted successfully in the fog chamber at high light conditions, which yielded high quality plants. A third experiment was conducted to evaluate the effect of chilling for four weeks at 3.3 degrees C, or spraying with gibberellic acid 3 (GA(3)) on post-rooting dormancy, a problem which frequently occurs with recently rooted apple microshoots. Chilled plants had greater dry mass than control or GA(3) plants, and the GA(3) effect was short-lived. The ex vitro procedure suggested by these experiments could reduce the time associated with rootstock micropropagation to at most 6 months.

A 2-year study was conducted to investigate the influence of the light environment on source-sink relationships in 'Titan' red raspberry. Treatments imposed included flower and cane removal in conjunction with partial or whole canopy shading. Raspberry plants were remarkably resistant to a reduction in carbon supply, Yields and primocane production were maintained even when canopies were shaded. Furthermore, if raspberry plants were prevented from producing a full crop in one year, yields the following year tended to be higher than normal. These data, and other studies demonstrating that raspberry roots are strong carbon sinks, suggest that raspberry plants may rely on stored carbohydrate to mature the current crop of fruits when current photosynthate is inadequate. This trait is characteristic of some perennial species adapted to progressively changing environments, but may not be optimal for horticultural situations where growing conditions are relatively constant from year to year. A large root storage capacity and excessive primocane production likely contribute to the relatively low yields that are typical of this species.

Seasonal changes in growth, mean maximal photosynthetic rates, and the temperature and light response curves of `Titan' red raspberry ( Rubus idaeus L.) were obtained from potted plants grown under field conditions. Primocane dry weight accumulation increased steadily at the beginning and the end of the season, but growth slowed midseason during fruiting. The slower midseason dry-weight accumulation rate coincided with an increase in root dry weight. Primocane net assimilation rate (NAR) was highest early in the season. Floricane photosynthetic rates (A) were highest during the fruiting period, while primocane A remained steady throughout the season. Primocane and floricane leaflets displayed a midday depression in A under field conditions, with a partial recovery in the late afternoon. Photosynthetic rates of primocane and floricane leaves were very sensitive to temperature, exhibiting a decline from 15 to 40C. Light-response curves differed depending on cane type and time of year. A temporal convergence of sink demand from fruit, primocanes, and roots occurs when plants experience high temperatures. These factors may account for low red raspberry yield.

A protocol is presented that enables a propagator to produce field-sized blueberry transplants within 6 months of obtaining microshoots from tissue culture. The protocol involves subjecting microshoots to ex vitro rooting in a fog chamber under 100 μmol·m –2 ·s –1 photosynthetic photon flux for 7 weeks, transferring plants to a fog tunnel for 2 weeks, then to a greenhouse for 7 more weeks. Plant survival and rooting of cultivars Berkeley ( Vaccinium corymbosum L.) and Northsky ( Vaccinium angustifolium × corymbosum ) were near 100% under these conditions. Plantlets in fog chambers receiving 100 μmol·m –2 ·s –1 grew rapidly, while those at lower irradiance levels grew more slowly, and supplemental CO 2 enhanced growth only at 50 μmol·m –2 ·s –1 . Growth rates slowed when plants were moved into the fog tunnel; but by the end of 16 weeks, plants that were under high irradiance in the fog chamber had root systems that were 15 to 30 times larger than plants under low irradiance. Within 6 months, these plants were 30 to 60 cm tall and suitable for field planting.

Flower bud and leaf samples collected from a wide range of native North American Vaccinium populations were tested for the presence of blueberry shoestring virus (BBSSV) using the enzyme-linked immunosorbant assay. The highest disease incidence was found in Michigan (14%), although a few positive samples also were found in Virginia, New Jersey, Maine, Ontario, and Quebec. Of seven species tested, only V. corymbosum L. and V. angustifolium Ait. were infected with BBSSV.

Longitudinally mowing rows to half their width and the V-trellis system were used to separate fruiting canes from primocanes in a raspberry ( Rubus idaeus and R. neglectus ) planting. The effects of these two systems on yield and its components were determined in 1985 and 1986 for the red raspberry ‘Titan’ and the purple raspberry ‘Royalty’. Both systems were compared to a standard I-trellis configuration, in which primocanes and floricanes grow together. Yields for both cultivars were significantly higher with the V-trellis than with the I-trellis system. Longitudinal mowing reduced yields in the V-trellis, but plots that were mowed outperformed the standard I-trellis. ‘Titan’ was more responsive to cane manipulation than ‘Royalty.’

Effects of annual pruning, alternate-year mowing, and primocane suppression on yield and its components for ‘Titan’ and ‘Royalty’ summer-bearing raspberries ( Rubus idaeus and R. neglectus ) were measured for 2 consecutive years. Cumulative yield was highest for primocane suppression and lowest for alternate-year mowing. Path analysis revealed that cane number per plant and number of fruitful laterals per cane were the most important yield components for both cultivars. Alternate-year mowing plots had higher cane numbers per plant than other treatments, but fewer fruitful laterals in the bottom and middle thirds of the canes. Annual primocane suppression increased numbers of fruitful laterals in the bottom and middle thirds of canes, resulting in increased yield compared to other treatments. Productivity was related to the amount of photosynthetically active radiation entering the canopy.

Abstract Plants of chrysanthemum ( Dendranthema grandiflora Tzvelev.) were grown under one of 25 irradiance and temperature combinations from start of short days to flower. Four phases of development were defined as 1) the start of short days to the appearance of 4-mm terminal flower buds (phase I), 2) appearance of 4-mm terminal flower buds to removal of lateral flower buds when the terminal flower bud was 7 to 8 mm (phase II), 3) removal of lateral flower buds to flower buds showing first color (phase III), and 4) flower buds showing color to flowering (phase IV ). Path analysis was used to study the influence of development time and relative dry weight gain during each of these four phases on development time and relative dry weight gain of subsequent phases. Relative dry matter accumulation during phases I, II, III, and IV significantly influenced cumulative relative dry weight gain, with phase I having the greatest influence. Increasing relative dry weight gain during phase I had a significant negative effect on relative dry weight gain in phase II. Time within each phase significantly affected total time to flower. Under the constant environmental conditions of this experiment, time in one phase did not influence the length of time in later phases.

Flower bud injury was assessed in 18 cultivars of highbush blueberry ( Vaccinium corymbosum L.) after two spring frosts. Bud position on shoots was significantly correlated ( P < 0.05) with percent brown ovaries. Significant differences in proportion of brown ovaries were noted among cultivars, but most of the variation was associated with stage of bud development. The least-developed buds were the most hardy. Bloom date was significantly correlated with harvest date across cultivars, although ‘Spartan’ flowered much later than other early ripening cultivars.

Abstract Blueberry shoestring virus (BBSSV) is the most serious disease in Michigan, and it has been reported in New Jersey, Washington, North Carolina, and Nova Scotia (4, 8). Shoestring is particularly difficult to eradicate, since there is no known control other than removing diseased bushes, and infected bushes do not show external symptoms for up to 4 years. Also, no cultivars of highbush blueberry are immune to the disease (2).

The proportion of annual biomass production allocated to various vegetative and reproductive tissues was measured in differently aged individuals of Vaccinium corymbosum from native populations in southern Michigan. The relationship between age and allocation was determined and a lifetime pattern of biomass partitioning was developed. The proportion of biomass allocated to reproduction was higher than many have predicted for woody species, and the relationship between age and reproductive effort did not conform to optimality models. In addition, reproductive performance was not affected by previous growth or reproduction. The basis of this complex reproductive behavior was examined by quantifying the relationships among components of reproduction. In general, yield components behaved independently within a season. A high potential reproductive effort coupled with yield component independence may be an adaptation to fluctuating environments.

Several genotypes of Vactinium angustifolium were taken at random from 17 environmentally diverse sites in Michigan and transplanted to a common greenhouse environment. During the 2nd season of growth, genotypes from southern sites exhibited significantly greater numbers of inflorescence buds than northern sites. Genotypes from sites with low light levels exhibited greater numbers of inflorescence buds and flowers per bud than those from sites with high light levels. Genotypes from dry sites produced larger fruit than genotypes from wet sites. These data suggest that environments exist in which natural selection has favored horticulturally desirable traits.

PRITTS, M. P. AND J. F. HANCOCK (Department of Pomology, Cornell University, Ithaca, NY 14853 and Department of Horticulture, Michigan State University, East Lansing, MI 48824). Independence of life history parameters in populations of Vaccinium angustifolium (Ericaceae). Bull. Torrey Bot. Club. 111: 451-461. 1984.-Many predictions concerning optimal patterns of resource partitioning imply that limiting resources are shared among several life history components, and this results in trade-offs (negative correlations) among the competing components. This implication was examined by measuring covariation among several life history traits and yield components in 13 diverse populations of Vaccinium angustifolium Ait. A principal component analysis revealed little covariation among life history parameters even though there was substantial variation in individual traits. Yield components also exhibited independent or slightly additive interactions and only one negative relationship was observed. Environmental factors were also strongly associated with life history and demographic variables. These results suggested that resource sharing does not always occur among life history parameters possibly because 1) components of growth and reproduction often are regulated by different limiting resources, 2) shared resources may not be limiting, and 3) natural selection may favor those individuals which minimize resource sharing through asynchronous periods of component development.