Twenty blueberry (Vaccinium sp. L.) families were planted in Michigan and Oregon to determine variability among families, locations and the importance of family×location interaction. The families were generated at Michigan State University from crosses among parents with a diverse genetic background. Seedlings were planted in field locations in Corvallis, Ore., and East Lansing, Mich., in 1995 and managed following standard commercial blueberry production practices with no insecticide or fungicide applications. In 1998-2000 the plants were evaluated for survival, bloom date, ripening date, plant growth and the fruit were scored for crop load, color, picking scar, firmness and size. All traits, except fruit color, varied significantly between locations. Plants in Oregon had a 36% greater survival rate and grew to be much larger, 80% taller and 104% wider, than those in Michigan. Families in Oregon flowered earlier in the year than those in Michigan but ripened at a similar time. Between locations, family differences were only evident for survival and fruit color. In Oregon, there were differences among families for all traits whereas in Michigan only survival, ripening date, plant height and width, and picking scar differed significantly. The family × environment interaction was not significant for crop load, fruit color and fruit firmness, so individuals selected on the basis of crop load, fruit color and fruit firmness should perform similarly in either location. There was a significant family × environment interaction for the other traits including survival, bloom date, ripening date, ripening interval, plant height and width, and for picking scar. Therefore, there is a need for individual selection programs at each location. Genotypes well adapted to Michigan may also do well in Oregon, but numerous promising genotypes could be missed for Oregon, if families are first selected in Michigan. The loss of numerous individuals due to winter cold may have reduced levels of variability in Michigan.
C.E. Finn, J.F. Hancock, T. Mackey, and S. Serçe
Ronald G. Goldy and Paul M. Lyrene
Methods of producing 8x plants from 4x V. corymbosum clones through in vitro colchicine treatments were investigated. Colchicine concentrations and exposure times ranged from 0.001% to 0.2% and 1 to 14 days, respectively. Pretreatments designed to predispose the plants to the effect of colchicine also were investigated. Eleven 8x plants and one 4x-8x chimera were selected from pretreated plants exposed to 0.025% or 0.05% colchicine. The superior treatment was 0.025% with a 24- or 48-hr exposure time in liquid medium. No differences were noted between warm/dark and cold/dark pretreatments. No differences were observed among 24-, 48-, 96-, and 192-hr growth intervals between cold pretreatment and colchicine treatment. However, a significant genotype effect in response to colchicine was found, both with respect to culture survival and polyploid induction.
C. Stushnoff and Ascunia J. Feliciano
The problem of observing pollen tube development and mitotic division can often be difficult and the technique can be unreliable. The following method was used with very good success for periodic observation of pollen tube development of several species of Vaccinium.
John C. Beaulieu, Rebecca E. Stein-Chisholm, and Deborah L. Boykin
There are very few studies detailing the aroma, astringency, and flavor of rabbiteye blueberry [RAB (Vaccinium ashei)] fruit typically grown in the southeastern United States. The objectives were to investigate the rapid and qualitative solid-phase microextraction gas chromatographic–mass spectrometry volatile composition of several local RAB cultivars with an overall goal to build a database of possible flavor and aroma compounds. Volatile profiles were obtained in five Louisiana-grown RAB cultivars (Brightwell, Climax, Premier, Powder Blue, and Tifblue) assayed at four maturities. The method routinely captured 53 volatiles, including 12 aldehydes, six alcohols, 11 esters, four ketones, 17 terpenoids, one furan, and two aromatics. Of the 33 compounds considered important in blueberries, 17 were recovered in the RAB cultivars assessed. Herein, 10 compounds were recovered for the first time in blueberry (Vaccinium sp.) and five of those compounds were confirmed with standards [2-ethylfuran, (E)-2-pentenal, (Z)-dehydroxylinalool oxide, (E)-dehydroxylinalool oxide and 1,4-cineole]. In general, terpenoids and their subclass linalools were the most significant volatiles followed closely by esters, aldehydes, and then alcohols. Terpenoids and linalools displayed the greatest significant differences in ‘Powder Blue’ and ‘Premier’. Esters and aldehydes were the most significant compound classes based on cultivar effect per maturity in firm-ripe fruit. From the suite of 17 of the 33 important compounds in upright blueberry, 10 were recovered across the five cultivars at four maturities that displayed a high level of significance. These were linalool, methyl 3-methylbutanoate, 1,8-cineole, (E)-2-hexanal, (Z)-3-hexenal, (Z)-3-hexenyl acetate, limonene, hexyl acetate, hexanal, and α-terpineol. These data will be useful to evaluate aroma volatiles in RAB and changes in processed and value-added byproducts.
Tripti Vashisth and Anish Malladi
A better understanding of fruit detachment and the processes mediating it is essential to improve the efficiency of mechanical harvesting in blueberry (Vaccinium sp.). In blueberry, fruit detachment may occur either at the point of attachment of the pedicel to the peduncle [peduncle–pedicel junction (PPJ)] or at the point of attachment of the pedicel to the fruit [fruit–pedicel junction (FPJ)]. The fruit detachment responses of the PPJ and the FPJ to different conditions are not entirely clear. Additionally, whether fruit detachment at these junctions is mediated by the physiological process of abscission or through physical separation of the organ from the parent plant is not well understood. In this study, a series of experiments were performed to determine the abscission zone (AZ) corresponding to the point of mature fruit detachment and to determine whether fruit detachment occurs as a result of abscission or physical separation in rabbiteye blueberry (Vaccinium ashei). Anatomical studies indicated the presence of an AZ at the PPJ. Greater than 92% of the natural detachment of mature fruit occurred at the PPJ. The morphology of the fracture plane at the PPJ in naturally detached fruit was even and uniform, consistent with fruit detachment through abscission at this location. Abscission agents such as methyl jasmonate (20 mm) and ethephon (1000 mg·L−1) enhanced the extent of fruit detachment at the PPJ, further indicating that mature fruit detachment through abscission occurred primarily at this location. Additionally, the fracture plane at the PPJ during fruit detachment in response to abscission agent applications was flattened and even, further supporting the conclusion that fruit detachment at this location occurred through abscission. In contrast, the majority of the fruit detachment in response to mechanical shaking occurred at the FPJ. Analysis of the morphology of the fracture plane at the FPJ during detachment in response to mechanical shaking indicated that fruit detachment at this location was associated with extensive tearing and mechanical disruption of cells, consistent with physical separation. Together, data from this study indicate that mature fruit detachment resulting from abscission occurs primarily at the PPJ, whereas fruit detachment during mechanical shaking occurs primarily at the FPJ as a result of physical breakage at this weak junction.
Bernadine C. Strik, Amanda J. Davis, Patrick A. Jones, and Chad E. Finn
‘Mini Blues’ highbush blueberry (Vaccinium sp.) was released in 2016 as a high-quality, machine-harvestable alternative to lowbush (V. angustifolium Ait.) or other small-fruited highbush blueberry cultivars for processed markets. A planting was established in Oct. 2015 in western Oregon to evaluate the effects of pruning method on yield, machine-harvest efficiency (MHE), berry weight and total soluble solids (TSS), leaf tissue nutrients, pruning weight, pruning time, and costs. Plants were pruned for shape and to remove flower buds in 2015–16 and 2016–17. Pruning treatments began in 2017–18 and included: 1) conventional highbush pruning (HB); 2) removing one or two of the oldest canes per bush (Speed); 3) leaving plants to grow from 2017 to 2021 (Unpruned) before doing a hard renovation prune in 2021–22 (cutting the plants back to a height of ≈0.3 m and leaving the best 8–10 canes/plant); and 4) hedging after fruit harvest in 2018 (Hedge) and then unpruned afterward until renovation in 2021–22. The pattern of yield progression, observed wood aging, and reduced berry size after 4 years of no pruning indicated renovation was necessary in the unpruned and hedge treatments. Low growth was removed each year in all treatments, and hedging was only done in 2018 because it severely reduced yield the following year and, therefore, was not a viable option. An over-the-row machine harvester was used from 2018 to 2021. Speed-pruned plants, averaged over 4 years, had the greatest potential yield (3.75 kg/plant) compared with the other treatments (averaged 2.99 kg/plant) but had a similar yield as HB because more fruit remained on the bush after harvest with speed pruning. In 2021, speed pruning resulted in the highest yield (4.2 kg/plant), followed by HB (3.8 kg/plant) and the unpruned and hedge methods (averaged 3.1 kg/plant). MHE increased from 43% in 2018 to 74% in 2021, mainly because, as the plants aged, a larger proportion of the canopy was above the catcher plates on the harvester. On average, MHE was highest with HB pruning (70%), intermediate in the unpruned and speed-pruned plants (59%), and lowest in the hedged plants (49%). In 2021, ground drop loss was highest for hedge (18%), lowest for speed (14%), and intermediate for HB and unpruned (averaged 16%) methods. HB-pruned plants had heavier berries (0.64 g) than unpruned and hedge treatments (averaged 0.57 g) and a similar berry weight as the speed-pruned plants (0.61 g). Pruning had no effect on berry TSS. In contrast to leaf K, leaf Mg and Ca concentrations were lowest in HB and higher in all other treatments. In 2020–21, HB pruning required 471 h·ha−1, while speed pruning took 79 h·ha−1; the hedge and unpruned treatments required an average of 60 h·ha−1 to remove low-growing branches that would interfere with machine harvest. In 2021–22, renovation of the unpruned and hedge treatments took 290 h·ha−1. While leaving bushes unpruned during establishment appears to be a promising option for ‘Mini Blues’, further work is needed to evaluate fruit production after renovation and to determine how long the plants could remain unpruned thereafter. Speed pruning is also a good option, reducing pruning costs by 85%.
Ann Marie Connor, James J. Luby, and Cindy B.S. Tong
Narrow-sense heritability and among-family and within-family variance components were estimated for antioxidant activity (AA), total phenolic content (TPH), and anthocyanin content (ACY) in blueberry (Vaccinium L. sp.) fruit. AA, TPH, and ACY were determined in the parents and in 10 offspring from each of 20 random crosses for each of 2 years at Becker, Minn. Offspring-midparent regression analysis provided combined-year heritability estimates of 0.43 ± 0.09 (P ≤ 0.0001) for AA, 0.46 ± 0.11 (P ≤ 0.0001) for TPH, and 0.56 ± 0.10 (P ≤ 0.0001) for ACY. Analyses of variance delineated variation among and within families for AA, TPH, and ACY (P ≤ 0.001). Year-to-year variation in the means for all offspring genotypes was not significant for AA or TPH, but there were changes in rank between years for families and for offspring within families for these traits. Year-to-year variation in the mean for all offspring genotypes was significant for ACY, but rank changes were observed only among offspring within families, not among families. In total, 18 of 200 offspring from 7 of the 20 crosses were transgressive segregants for AA, exceeding the higher parent of the cross by at least two sds. Estimates of variance components showed that variation among families accounted for 24% to 27% of total variance for the three traits. However, variation within families was greater than that among families, accounting for 38% to 56% of total variance for the three traits. These results suggest that increasing antioxidant activity in blueberry through breeding is feasible, and that the breeding strategies utilized should exploit the large within-family variation that exists.
W. B. Sherman and R. H. Sharpe
‘Beckyblue’ (Fig. 1)has been released by the University of Florida, Institute of Food and Agricultural Sciences Fruit Crops Department. It fills the need for a rabbiteye type blueberry in North and Central Florida which will fruit consistently in years of high and low winter chilling.
W. B. Sherman and R. H. Sharpe
‘Aliceblue’ (Fig. 1) has been released by the University of Florida, Institute of Food and Agricultural Sciences Fruit Crops Department. It fills the need for a rabbiteye type blueberry in North and Central Florida which will fruit consistently in years of high and low winter chilling.