Gerard Krewer

Effects of Blueberry (Vaccinium ashei) on DNA Damage, Lipid Peroxidation, and Phase II Enzyme Activities in Rats

Blueberry extracts have high antioxidant potential and increase phase II enzyme activities in vitro. This study tested the hypothesis that blueberries would reduce DNA damage and lipid peroxidation and increase phase II enzyme activities in vivo. Young, healthy male Sprague-Dawley rats (n = 8 per group) were fed control AIN-93 diets or AIN-93 diets supplemented with blueberries or blueberry extracts for 3 weeks. Diets were supplemented with 10% freeze-dried whole blueberries, blueberry polyphenol extract and sugars to match the 10% blueberry diet, or 1 and 0.2% blueberry flavonoids, which were primarily anthocyanins. Liver and colon mucosa glutathione-S-transferase (GST), quinone reductase, and UDP-glucuronosyltransferase activities in colon mucosa and liver were not significantly increased by freeze-dried whole blueberries or blueberry fractions. Liver GST activity, however, was approximately 25% higher than controls for the freeze-dried whole blueberry, blueberry polyphenol, and 1% flavonoid groups. DNA damage was significantly lower than control only in the liver of animals fed the 1% flavonoid diet. The level of urinary F(2)-isoprostanes, a measure of lipid peroxidation, was unaffected. In summary, in healthy rats, short-term supplementation with freeze-dried whole blueberries, blueberry polyphenols, or blueberry flavonoids did not significantly increase phase II enzyme activities. However, supplementation with 1% blueberry flavonoids did decrease oxidative DNA damage in the liver.

A Survey of Horticultural and Pest Management Practices of the Georgia Blueberry Industry

Abstract A producer survey was conducted in January 1999 to collect data on current production practices as well as present and future needs of the Georgia blueberry industry. A questionnaire requested anonymous information on various aspects of production, pest management, and pesticide use in addition to soliciting producer perceptions of the importance of horticultural and pest problems. The survey, which accounted for more than 45% of the states bearing blueberry acreage, showed that production continues to be concentrated in the southeastern and south-central parts of the state. On average, producers had 14.3 years of experience in growing blueberries, indicating that the industry has matured considerably during the past decade. Prominent changes in production include increased plantings of southern highbush cultivars and an increased percentage of the crop being produced for the fresh market. In addition, pest problems have become more noteworthy, illustrated by the fact that more than 80% of producers now use fungicides. The most common horticultural problems identified were poor fruit set, drought, and freeze-related problems. Overall, the survey suggests that Georgias blueberry industry is healthy and expanding, with a projected increase in the area planted by more than 35% by 2005.

Imidacloprid Insecticide Slows Development of Pierce's Disease in Bunch Grapes

Six cultivars of bunch grapevines Vitis labrusca (L.) and V. vinifera (L), ‘Cabernet Franc’, ‘Canadice’, ‘Flame Seedless’, ‘Johannesburg Riesling’, ‘Mars’ and ‘Reliance’ when treated at planting an...

Blueberry Postharvest Disease Detection Using an Electronic Nose

In the United States, cultivated blueberries are second only to strawberries as one of the most important berries. In Georgia, the blueberry industry has grown by 170% in economic value between 2000 and 2005 and has become Georgia’s most important fruit crop with a total farm gate value exceeding

Growing Organic Rabbiteye Blueberries in Georgia, USA: Results of Two Multi-Year Field Studies

75 million. However, blueberries are also a highly perishable fruit, and more than 20% of the berries are typically lost before they get to consumers. Furthermore, physical damage renders blueberry fruit more susceptible to certain fungal diseases such as gray mold (Botrytis cinerea), anthracnose (Collecotrichum spp.), and Alternaria rot (Alternaria spp.). A conducting polymer gas sensor array was evaluated for detecting and classifying blueberry fruit infected with these three common fungal postharvest pathogens. Samples of rabbiteye blueberries (Vaccinium virgatum cv. Brightwell) were inoculated individually with one of the three pathogens or left uninoculated, and volatiles emanating from the fruit were assessed using a gas sensor array 6-10 days after inoculation in two separate experiments. Principal component analysis revealed four distinct groups corresponding to the four inoculation treatments. A hierarchical cluster analysis indicated two super-clusters, i.e., control cluster (non-inoculated fruit) vs. pathogen cluster (inoculated fruit). Within the pathogen cluster, fruit infected by B. cinerea and Alternaria sp. were more similar to each other than to fruit infected by C. gloeosporioides. A linear Bayesian classifier achieved 90% overall correct classification for combined data from two experiments. Gas chromatography-mass spectrometry identified six compounds [styrene, 1-methyl-2-(1-methylethyl) benzene, eucalyptol, undecane, 5-methyl-2-(1-methylethyl)-2-cyclohexen-1-one, and thujopsene] that contributed the most in distinguishing differences in the volatiles emanating from the fruit due to infection. This study underscores the potential feasibility of using a gas sensor array for blueberry postharvest quality assessment and fungal disease detection.

Abundance and Consumption Rate of Glassy-Winged Sharpshooter (Hemiptera: Cicadellidae) on Peaches and Plums

South Georgia is a major blueberry production region located in the warm and humid northern subtropics. The region enjoys a favorable market window, but pressure from weeds, insects, and diseases raised questions as to whether organic production would be feasible in this climatic zone. Two multi-year field studies were conducted to determine the best practices for organic culture of blueberries and to compare yields with conventional production. Various methods of weed control were tested. While organic burn-down herbicides performed poorly on the grasses that are the dominating weeds in blueberry in southern Georgia, mulches and a rolling cultivator were successful in maintaining a weed-free strip on the side of the organic beds. Hand-weeding was needed at the interface between the mulches and the cultivated strip. Pine straw and pine bark mulch resulted in the lowest hand-weeding times, whereas pine bark and wheat straw were the highest-yielding treatments. Some other locally available plant-derived or synthetic mulches also performed well for organic blueberry establishment, hence, the decision as to which mulch to use can be based partly on availability of local resources. A separate 6-year study compared yields in conventional and organic production systems. Weed problems in year 1 caused the growth of the organically managed plants to fall behind those grown conventionally, but over time very good yields (ca. 5,900 kgu2009/ha) were produced by the organic method using pine bark mulch, and net returns over the 6-year period were higher than conventional. Organic production of rabbiteye blueberries in Georgia appears commercially feasible.

Disease Management in Organic Rabbiteye Blueberries

Homalodisca vitripennis (Germar), the glassy-winged sharpshooter, is a primary vector of phony peach and plum leaf scald diseases caused by Xylella fastidiosa Wells et al. A survey of H. vitripennis on peach [Prunus persica (L.) Batsch] varieties established that leafhopper abundances varied from 0–13 per tree. Prunus persica cvs. Flordaking and June Gold and Prunus salicina Lindl. (cvs. Methley and Santa Rosa) were then budded on each of 3 P. persica rootstocks (cvs. Aldrighi, Lovell and Nemaguard). Leafhopper abundance was monitored on each of the two scions budded on each rootstock and on non budded rootstocks over a 2-yr period. The genotypes were container-grown in Year 1 and were planted in the field in Year 2. For both years leafhopper abundance was greatest during early June and on Methley and Santa Rosa cultivars compared with the peach genotypes. The feeding rates of leafhoppers were substantially higher on plum scions than on peach scions, and nocturnal feeding rates were often higher than dayt...

Phenolic compounds and antioxidant capacity of Georgia-grown blueberries and blackberries.

ABSTRACT Non-indigenous fruit crops such as peaches, apples, and vinifera grapes have limited potential for organic production in the southeastern United States due to the substantial pest pressures associated with the long growing season and the warm, humid climate. In contrast, rabbiteye blueberries, which comprise a large majority of the blueberry acreage in the Southeast, are native to the region and are well adapted to cope with its challenging climate, poor soils, and extensive pest complexes. Although rabbiteye blueberries are resistant to several important diseases affecting other blueberry species, all rabbiteye cultivars appear susceptible to mummy berry disease and most are affected by one or more foliar diseases such as Septoria leaf spot, Gloeosporium leaf spot, and/or leaf rust. This article briefly reviews old and new approaches for controlling these diseases organically. Mummy berry can be managed by pathogen exclusion, soil cultivation against overwintering primary inoculum, and application of a Bacillus subtilis-based biofungicide against secondary infection of flowers. For foliar diseases, host resistance is the first line of defense, whereas fish oil-based biofungicides have provided promising levels of disease suppression on susceptible cultivars. Knowledge gaps and future research needs are discussed.